Toll-like receptor-4 and mitogen-activated protein kinase signal system are involved in activation of dendritic cells in patients with acute coronary syndrome

Transcriptional control of metabolism by interferon regulatory factors

Interferon regulatory factors (IRFs) comprise a family of nine transcription factors in mammals. IRFs exert broad effects on almost all aspects of immunity but are best known for their role in the antiviral response. Over the past two decades, IRFs have been implicated in metabolic physiology and pathophysiology, partly as a result of their known functions in immune cells, but also because of direct actions in adipocytes, hepatocytes, myocytes and neurons. This Review focuses predominantly on IRF3 and IRF4, which have been the subject of the most intense investigation in this area. IRF3 is located in the cytosol and undergoes activation and nuclear translocation in response to various signals, including stimulation of Toll-like receptors, RIG-I-like receptors and the cGAS-STING pathways. IRF3 promotes weight gain, primarily by inhibiting adipose thermogenesis, and also induces inflammation and insulin resistance using both weight-dependent and weight-independent mechanisms. IRF4, meanwhile, is generally pro-thermogenic and anti-inflammatory and has profound effects on lipogenesis and lipolysis. Finally, new data are emerging on the role of other IRF family members in metabolic homeostasis. Taken together, data indicate that IRFs serve as critical yet underappreciated integrators of metabolic and inflammatory stress.

Extracellular vesicles of iPS cells highly capable of producing HGF and TGF-β1 can attenuate Sjögren's syndrome via innate immunity regulation

Previous studies have demonstrated that extracellular vesicles (EVs) from dental pulp stem cells (DPSCs), which release abundant hepatocyte growth factor (HGF) and transforming growth factor-β1 (TGF-β1), contribute to the pathogenesis of Sjögren's syndrome (SS). However, depending on the condition of DPSCs, this effect is often not achieved. In this study, we established induced pluripotent stem (iPS) cells highly capable of releasing HGF and TGF-β1 and iPS cells barely capable of releasing them, and administered each EV to SS model mice to see if there was a difference in therapeutic effect. EVs were collected from each iPS cell and their characteristics and shapes were examined. When they were administered to SS model mice, the EVs from iPS cells with higher concentrations of HGF and TGF-β1 showed significantly reduced inflammatory cell infiltration in salivary gland tissues, increased saliva volume, and decreased anti-SS-A and anti-SS-B antibodies. A comprehensive search of microRNA arrays for differences among those EVs revealed that EVs from iPS cells with higher concentrations of HGF and TGF-β1 contained more of the let-7 family. Thereafter, we examined the expression of toll-like receptors (TLRs), which are said to be regulated by the let-7 family, by qPCR, and found decreased TLR4 expression. Focusing on MAPK, a downstream signaling pathway, we examined cytokine concentrations in mouse macrophage culture supernatants and Western blotting of murine splenic tissues and found higher concentrations of anti-inflammatory cytokines in the EVs-treated group and decreased TLR4, NF-κB and phosphorylation (p)-p-38 MAPK expression by Western blotting. Alternatively, p-Smad2/3 was upregulated in the EVs-treated group. Our findings suggest that the let-7 family in EVs may suppress the expression of TLR4 and NF-κB, which may be involved in the suppression of MAPK-mediated pro-inflammatory cytokine production.

Drugs to Treat Neuroinflammation in Neurodegenerative Disorders

Neuroinflammation is associated with disorders of the nervous system, and it is induced in response to many factors, including pathogen infection, brain injury, toxic substances, and autoimmune diseases. Astrocytes and microglia have critical roles in neuroinflammation. Microglia are innate immune cells in the central nervous system (CNS), which are activated in reaction to neuroinflammation-inducing factors. Astrocytes can have pro- or anti-inflammatory responses, which depend on the type of stimuli presented by the inflamed milieu. Microglia respond and propagate peripheral inflammatory signals within the CNS that cause low-grade inflammation in the brain. The resulting alteration in neuronal activities leads to physiological and behavioral impairment. Consequently, activation, synthesis, and discharge of various pro-inflammatory cytokines and growth factors occur. These events lead to many neurodegenerative conditions, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis discussed in this study. After understanding neuroinflammation mechanisms and the involvement of neurotransmitters, this study covers various drugs used to treat and manage these neurodegenerative illnesses. The study can be helpful in discovering new drug molecules for treating neurodegenerative disorders.

Montelukast and Acute Coronary Syndrome: The Endowed Drug

Acute coronary syndrome (ACS) is a set of signs and symptoms caused by a reduction of coronary blood flow with subsequent myocardial ischemia. ACS is associated with activation of the leukotriene (LT) pathway with subsequent releases of various LTs, including LTB4, LTC4, and LTD4, which cause inflammatory changes and induction of immunothrombosis. LTs through cysteine leukotriene (CysLT) induce activation of platelets and clotting factors with succeeding coronary thrombosis. CysLT receptor (CysLTR) antagonists such as montelukast (MK) may reduce the risk of the development of ACS and associated complications through suppression of the activation of platelet and clotting factors. Thus, this critical review aimed to elucidate the possible protective role of MK in the management of ACS. The LT pathway is implicated in the pathogenesis of atherosclerosis, cardiac hypertrophy, and heart failure. Inhibition of the LT pathway and CysL1TR by MK might be effective in preventing cardiovascular complications. MK could be an effective novel therapy in the management of ACS through inhibition of pro-inflammatory CysLT1R and modulation of inflammatory signaling pathways. MK can attenuate thrombotic events by inhibiting platelet activation and clotting factors that are activated during the development of ACS. In conclusion, MK could be an effective agent in reducing the severity of ACS and associated complications. Experimental, preclinical, and clinical studies are recommended to confirm the potential therapeutic of MK in the management of ACS.

Microglia Phenotypes in Aging and Neurodegenerative Diseases

Neuroinflammation is a hallmark of many neurodegenerative diseases (NDs) and plays a fundamental role in mediating the onset and progression of disease. Microglia, which function as first-line immune guardians of the central nervous system (CNS), are the central drivers of neuroinflammation. Numerous human postmortem studies and in vivo imaging analyses have shown chronically activated microglia in patients with various acute and chronic neuropathological diseases. While microglial activation is a common feature of many NDs, the exact role of microglia in various pathological states is complex and often contradictory. However, there is a consensus that microglia play a biphasic role in pathological conditions, with detrimental and protective phenotypes, and the overall response of microglia and the activation of different phenotypes depends on the nature and duration of the inflammatory insult, as well as the stage of disease development. This review provides a comprehensive overview of current research on the various microglia phenotypes and inflammatory responses in health, aging, and NDs, with a special emphasis on the heterogeneous phenotypic response of microglia in acute and chronic diseases such as hemorrhagic stroke (HS), Alzheimer’s disease (AD), and Parkinson’s disease (PD). The primary focus is translational research in preclinical animal models and bulk/single-cell transcriptome studies in human postmortem samples. Additionally, this review covers key microglial receptors and signaling pathways that are potential therapeutic targets to regulate microglial inflammatory responses during aging and in NDs. Additionally, age-, sex-, and species-specific microglial differences will be briefly reviewed.

Toll receptor 2 (Toll2) positively regulates antibacterial immunity but promotes white spot syndrome virus (WSSV) infection in shrimp

The Toll family of receptors are a group of conserved pattern recognition receptors (PRRs) essentially controlling the initiation of innate immune responses. The white spot syndrome virus (WSSV) and Vibrio parahaemolyticus are major pathogens of aquaculture shrimp. Previous study has suggested that expression of the Toll2 receptor in Pacific white shrimp Penaeus vannamei was up-regulated by white spot syndrome virus (WSSV) infection but did not significantly changed upon infection with the bacterial pathogen Vibrio parahaemolyticus. The current study intends to investigate the role of P. vannamei Toll2 in antibacterial and antiviral immunity. We demonstrated that compared with the control, the Toll2-silenced shrimp was more susceptible to V. parahaemolyticus infection, suggesting that Toll2 may play a positive role in antibacterial immunity. However, silencing of Toll2 significantly enhanced survivorship of shrimp infected with WSSV and reduced the viral load in shrimp tissues. The expression of WSSV structural protein VP28 was also inhibited in Toll2-silenced shrimp. Histologic pathology analysis further showed that the WSSV infection was attenuated in stomach tissues from Toll2-silenced shrimp. These suggested that Toll2 could promote WSSV infection in shrimp. In Toll2-silenced shrimp, expression of antimicrobial peptides ALFs and PENs was significantly changed, which may contribute to the role of Toll2 in antibacterial immunity and WSSV infection.

Activation of TNFR1 and TLR4 following oxygen glucose deprivation promotes mitochondrial fission in C6 astroglial cells

Astrocytes have emerged as active players in the innate immune response triggered by various types of insults. Recent literature suggests that mitochondria are key participants in innate immunity. The present study investigates the role of ischemia-induced innate immune response on p65/PGC-1α mediated mitochondrial dynamics in C6 astroglial cells. OGD conditions induced astroglial differentiation in C6 cells and increased the expression of hypoxia markers; HIF-1α, HO-1 and Cox4i2. OGD conditions resulted in induction of innate immune response in terms of expression of TNFR1 and TLR4 along with increase in IL-6 and TNF-α levels. OGD conditions resulted in decreased expression of I-κB with a concomitant increase in phos-p65 levels. The expression of PGC-1α, a key regulator of mitochondrial biogenesis, was also increased. Immunochemical staining suggested that phos-p65 and PGC-1α was co-localized. Studies on mitochondrial fusion (Mfn-1) and fission (DRP1) markers revealed shift toward fission. In addition, mitochondrial membrane potential decreased with increased DNA degradation and apoptosis confirming mitochondrial fission under OGD conditions. However, inhibition of phos-p65 by MG132 reduced the co-localization of phos-p65/ PGC-1α and significantly increased the Mfn-1 expression. The findings demonstrate the involvement of TNFR1 and TLR4 mediated immune response followed by interaction between phos-p65 and PGC-1α in promoting fission in C6 cells under hypoxic condition.

Red yeast rice ameliorates high-fat diet-induced atherosclerosis in Apoe-/- mice in association with improved inflammation and altered gut microbiota composition

Gut microbiota plays an important role in many metabolic diseases and has been linked to cardiovascular disease, including atherosclerosis. Clinical studies suggest that red yeast rice (RYR) has the potential to reduce blood lipid levels. However, the mechanisms under which RYR regulates atherosclerosis by affecting the composition of the gut microbiome have not been elucidated. In the current study, results showed that treatment with RYR significantly decreased the plaque formation and levels of cholesterol and low-density lipoprotein (LDL) compared with the atherosclerotic model group which were fed with a high-fat diet. In addition, the height of enteral villus in the red Monascus group was increased, indicating that RYR can improve the intestinal barrier function. Further analysis revealed that RYR might attenuate atherosclerosis through inhibiting hydroxy methylglutaryl-CoA reductase and the consequent inflammatory signaling pathways mediated by TLR2 and TLR4. Moreover, the RYR treatment led to significant structural changes on the intestinal microbiota of high-fat diet-fed mice and reduced the relative abundance of Alistipes and Flavonifractor that exhibited positive relationships with the plasma levels of cholesterol and LDL. Collectively, these findings illustrated that RYR could significantly protect against atherosclerosis, which was possibly associated with the alterations in the gut microbiota composition.

Serum metabolite profiling of ST-segment elevation myocardial infarction using liquid chromatography quadrupole time-of-flight mass spectrometry

ST segment elevation myocardial infarction (STEMI) is one of the most common global causes of cardiovascular disease-related death. Several metabolites may change during STEMI. Hence, analysis of metabolites in body fluid may be considered as a rapid and accurate test for initial diagnosis. This study has therefore attempted to determine the variation in metabolites identified in the serum of STEMI patients (n = 20) and 15 controls. Samples collected from the Cardiology Department, Medical Faculty, Ataturk University, were extracted by liquid-liquid extraction and analysed using liquid chromatography quadrupole time-of-flight mass spectrometry. The METLIN database was used for the identification and characterization of metabolites. According to Q-TOF/MS measurements, 231 m/z values, which were significantly different between groups (P < 0.01 and fold analysis >1.5) were detected. Metabolite identification was achieved via the Human Metabolome database. According to the multivariate data analysis, leucine, isoleucine, l-proline, l-alanine, glycine, fumaric acid, citrate, succinate and carnitine levels were decreased, whereas levels of propionic acid, maleic acid, butyric acid, urea, oleic acid, palmitic acid, lysoPC [18:2(9Z)], glycerol, phoshpatidylethanolamine, caffeine and l-lactic acid were increased in STEMI patients compared with controls. In conclusion, malonic acid, maleic acid, fumaric acid and palmitic acid can be used as biomarkers for early risk stratification of patients with STEMI.

Immune-Inflammatory Responses in Atherosclerosis: The Role of Myeloid Cells

Inflammation plays a key role in the initiation and progression of atherosclerosis and can be caused by multiple agents, including increased concentration of circulating low-density lipoprotein (LDL) cholesterol. Areas of the arterial wall affected by atherosclerosis are enriched with lymphocytes and dendritic cells (DCs). Atherosclerotic plaques contain a variety of proinflammatory immune cells, such as macrophages, DCs, T cells, natural killer cells, neutrophils and others. Intracellular lipid accumulation in atherosclerotic plaque leads to formation of so-called foam cells, the cytoplasm of which is filled with lipid droplets. According to current understanding, these cells can also derive from the immune cells that engulf lipids by means of phagocytosis. Macrophages play a crucial role in the initial stages of atherogenesis by engulfing oxidized LDL (oxLDL) in the intima that leads to their transformation to foam cells. Dying macrophages inside the plaque form a necrotic core that further aggravates the lesion. Proinflammatory DCs prime differentiation of naïve T cells to proinflammatory Th1 and Th17 subsets. In this review, we discuss the roles of cell types of myeloid origin in atherosclerosis-associated inflammation.

Unveiling the Interplay between the TLR4/MD2 Complex and HSP70 in the Human Cardiovascular System: A Computational Approach

While precise mechanisms underlying cardiovascular diseases (CVDs) are still not fully understood, previous studies suggest that the innate immune system, through Toll-like receptor 4 (TLR4), plays a crucial part in the pathways leading to these diseases, mainly because of its interplay with endogenous molecules. The Heat-shock protein 70 family (HSP70-70kDa) is of particular interest in cardiovascular tissues as it may have dual effects when interacting with TLR4 pathways. Although the hypothesis of the HSP70 family members acting as TLR4 ligands is becoming widely accepted, to date no co-crystal structure of this complex is available and it is still unknown whether this process requires the co-adaptor MD2. In this study, we aimed at investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the human cardiovascular system through transcriptomic data analysis and at proposing a putative interaction model between these proteins. We report compelling evidence of correlated expression levels between TLR4 and MD2 with HSP70 cognate family members, especially in heart tissue. In our molecular docking simulations, we found that HSP70 in the ATP-bound state presents a better docking score towards the TLR4/MD2 complex compared to the ADP-bound state (-22.60 vs. -10.29 kcal/mol, respectively). Additionally, we show via a proximity ligation assay for HSP70 and TLR4, that cells stimulated with ATP have higher formation of fluorescent spots and that MD2 might be required for the complexation of these proteins. The insights provided by our computational approach are potential scaffolds for future in vivo studies investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the cardiovascular system.

Indoleamine 2,3-Dioxygenase (IDO) Enzyme Links Innate Immunity and Altered T-Cell Differentiation in Non-ST Segment Elevation Acute Coronary Syndrome

Atherosclerosis is a chronic inflammatory disease characterized by a complex interplay between innate and adaptive immunity. Dendritic cells (DCs) play a key role in T-cell activation and regulation by promoting a tolerogenic environment through the expression of the immunosuppressive enzyme indoleamine 2,3-dioxygenase (IDO), an intracellular enzyme involved in tryptophan catabolism. IDO expression and activity was analyzed in monocytes derived DCs (MDDCs) from non-ST segment elevation myocardial infarction (NSTEMI) patients, stable angina (SA) patients and healthy controls (HC) by real-time quantitative polymerase chain reaction (RT-qPCR) before and after in vitro maturation with lipopolysaccharide (LPS). The amount of tryptophan catabolite; kynurenine; was evaluated in the culture supernatants of mature-MDDCs by ELISA assay. Autologous mixed lymphocyte reaction (MLR) between mature-MDDCs and naïve T-cells was carried out to study the differentiation towards T-helper 1 (Th1) and induced regulatory T-cells (iTreg). Analysis of IDO mRNA transcripts in mature-MDDCs revealed a significant reduction in cells isolated from NSTEMI (625.0 ± 128.2; mean ± SEM) as compared with those from SA (958.5 ± 218.3; p = 0.041) and from HC (1183.6 ± 231.6; p = 0.034). Furthermore; the concentration of kynurenine was lower in NSTEMI patients (2.78 ± 0.2) and SA (2.98 ± 0.25) as compared with HC (5.1 ± 0.69 ng/mL; p = 0.002 and p = 0.016; respectively). When IDO-competent mature-MDDCs were co-cultured with allogeneic naïve T-cells, the ratio between the percentage of generated Th1 and iTreg was higher in NSTEMI (4.4 ± 2.9) than in SA (1.8 ± 0.6; p = 0.056) and HC (0.9 ± 0.3; p = 0.008). In NSTEMI, the tolerogenic mechanism of the immune response related to IDO production by activated MDDCs is altered, supporting their role in T-cell dysregulation.

Experimental study of the anti-atherosclerotic effect of demethylzeylasteral

This study aimed to confirm that atherosclerosis (AS) is a systemic immune-mediated chronic inflammatory disease and to investigate the anti-atherosclerotic effect of demethylzeylasteral by testing the immunocompetent cells and inflammatory mediators in the blood and atherosclerotic plaques of the rabbit model of AS. For this purpose, 60 male New Zealand white rabbits were given 150 g high-fat diet (1% cholesterol, 5% lard, and 15% egg yolk powder) daily for a total of 90 days. On day 61, the rabbits were randomly divided into the saline group (n=15), the rosuvastatin group (n=15), the low-dose demethylzeylasteral group (n=15), and the high-dose demethylzeylasteral group (n=15). The CD3⁺ T lymphocytes and the subsets CD4⁺, CD8⁺, and CD4⁺/CD8⁺, as well as the soluble interleukin-2 receptor (sIL-2R) were measured before and after the treatment. The contents of immunoglobulins IgG, IgA and IgM and the levels of complements C3 and C4 were also monitored. In addition, the level of anti-oxidized low-density lipoprotein (ox-LDL) antibody, the inflammatory cytokines tumor necrosis factor-α (TNF-α), IL-6 and metalloproteinase-9 (MMP-9), the blood lipids triglyceride (TG), total cholesterol (TC), LDL cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured, and the severity of plaque lesions was also evaluated. Our results showed that the saline group, the rosuvastatin group and the low-dose demethylzeylasteral group had significantly lower activated T lymphocyte parameters CD3⁺, CD4⁺, CD8⁺ and CD4⁺/CD8⁺ (P<0.05), and significantly higher levels of sIL-2R, immunoglobulins IgG, IgA and IgM, complements C3 and C4, anti-ox-LDL antibody, TNF-α, IL-6 and MMP-9 (P<0.01) when compared with the high-dose demethylzeylasteral group. Moreover, TG, TC, LDL-C contents were found significantly lower and their HDL-C contents were significantly higher in high-dose demethylzeylasteral group (P<0.01) as compared to the other three groups. Furthermore, Sudan staining and haematoxylin and eosin staining of the thoracic aorta showed that, after 30-day treatment, the high-dose demethylzeylasteral group had the smoothest intima and the lightest plaque lesions among the four groups. Based on these results, we concluded that AS is a systemic immune-mediated chronic inflammatory disease and the relatively high dose of demethylzeylasteral used in the treatment of atherosclerotic rabbits could significantly alleviate AS. This implies that demethylzeylasteral may be considered as a suitable drug for anti-immunization therapy.

Role of TLR4 and miR-155 in peripheral blood mononuclear cell-mediated inflammatory reaction in coronary slow flow and coronary arteriosclerosis patients

BACKGROUND

To study the role of toll-like receptor 4 (TLR4) and MicroRNA-155 (miR-155) in the peripheral blood mononuclear cell (PBMC)-mediated inflammation in coronary slow flow (CSF) and coronary arteriosclerosis.

METHODS

Patients were divided into acute coronary syndrome (ACS), stable angina pectoris (SAP), CSF, and healthy control (HC) groups. The isolated PBMCs were treated with lipopolysaccharide (LPS)/and antagomiR-155. TLR4, miR-155, and the concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1, and IL-10 were measured.

RESULTS

Before LPS intervention, the TLR4, TNF-α, IL-1, and IL-6 levels were higher and the level of miR-155, IL-10 was lower in the ACS group compared with the SAP, CSF, and HC groups. After exposure to LPS, the levels of TLR4, miR-155, TNF-α, IL-1, and IL-6 were increased and the level of IL-10 was decreased in the SAP and CSF groups compared with the HC group. But when over-expressing antagomiR-155 into PBMCs from SAP and CSF groups, the miR-155 expression, and TNF-α, IL-6, and IL-1 secretion increase induced by LPS were restrained.

CONCLUSIONS

TLR4, miR-155, and inflammatory cytokines may be closely related to ACS. LPS can induce TLR4, miR-155 expression and inflammatory response in SAP and CSF patients. AntagomiR-155 can inhibit this inflammatory response.

Inflammation-induced foam cell formation in chronic inflammatory disease

Atherosclerosis is the leading cause of cardiovascular disease and is both a metabolic and inflammatory disease. Two models describe early events initiating atherosclerotic plaque formation, whereby foam cells form in response to hyperlipidaemia or inflammation-associated stimuli. Although these models are inextricably linked and not mutually exclusive, identifying the unique contribution of each in different disease settings remains an important question. Circulating monocytes are key mediators of atherogenesis in both models as precursors to lipid-laden foam cells formed in response to either excess lipid deposition in arteries, signalling via pattern-associated molecular patterns or a combination of the two. In this review, we assess the role of monocytes in each model and discuss how key steps in atherogenesis may be targeted to enhance clinical outcomes in patients with chronic inflammatory disease.

Short-term exercise training improves insulin sensitivity but does not inhibit inflammatory pathways in immune cells from insulin-resistant subjects

Background. Exercise has an anti-inflammatory effect against, and immune cells play critical roles in the development, of insulin resistance and atherosclerotic vascular disease (AVD). Thus, the goal of this study was to determine whether exercise improves insulin sensitivity in insulin-resistant subjects by downregulating proinflammatory signaling in immune cells. Methods. Seventeen lean, 8 obese nondiabetic, and 11 obese type 2 diabetic individuals underwent an aerobic exercise program for 15 days and an insulin clamp before and after exercise. Peripheral mononuclear cells (PMNC) were obtained for determination of Toll-like receptor (TLR) 2 and 4 protein content and mitogen-activated protein kinase phosphorylation. Results. Compared with that in lean individuals, TLR4 protein content was increased by 4.2-fold in diabetic subjects. This increase in TLR4 content was accompanied by a 3.0-fold increase in extracellular signal-regulated kinase (ERK) phosphorylation. Exercise improved insulin sensitivity in the lean, obese, and type 2 diabetes groups. However, exercise did not affect TLR content or ERK phosphorylation. Conclusions. TLR4 content and ERK phosphorylation are increased in PMNC of type 2 diabetic individuals. While exercise improves insulin sensitivity, this effect is not related to changes in TLR2/TLR4 content or ERK phosphorylation in PMNC of type 2 diabetic individuals.

Salvianolic acid B suppresses maturation of human monocyte-derived dendritic cells by activating PPARγ

BACKGROUND AND PURPOSE

Salvianolic acid B (Sal B), a water-soluble antioxidant derived from a Chinese medicinal herb, is known to be effective in the prevention of atherosclerosis. Here, we tested the hypothesis that the anti-atherosclerotic effect of Sal B might be mediated by suppressing maturation of human monocyte-derived dendritic cells (h-monDC).

EXPERIMENTAL APPROACH

h-monDC were derived by incubating purified human monocytes with GM-CSF and IL-4. h-monDC were pre-incubated with or without Sal B and stimulated by oxidized low-density lipoprotein (ox-LDL) in the presence or absence of PPARγ siRNA. Expression of h-monDC membrane molecules (CD40, CD86, CD1a, HLA-DR) were analysed by FACS, cytokines were measured by elisa and the TLR4-associated signalling pathway was determined by Western blotting.

KEY RESULTS

Ox-LDL promoted h-monDC maturation, stimulated CD40, CD86, CD1a, HLA-DR expression and IL-12, IL-10, TNF-α production; and up-regulated TLR4 signalling. These effects were inhibited by Sal B. Sal B also triggered PPARγ activation and promoted PPARγ nuclear translocation, attenuated ox-LDL-induced up-regulation of TLR4 and myeloid differentiation primary-response protein 88 and inhibited the downstream p38-MAPK signalling cascade. Knocking down PPARγ with the corresponding siRNA blocked these effects of Sal B.

CONCLUSIONS AND IMPLICATIONS

Our data suggested that Sal B effectively suppressed maturation of h-monDC induced by ox-LDL through PPARγ activation.

Dendritic cells in human atherosclerosis: from circulation to atherosclerotic plaques

Background. Atherosclerosis is a chronic inflammatory disease with atherosclerotic plaques containing inflammatory infiltrates predominantly consisting of monocytes/macrophages and activated T cells. More recent is the implication of dendritic cells (DCs) in the disease. Since DCs were demonstrated in human arteries in 1995, numerous studies in humans suggest a role for these professional antigen-presenting cells in atherosclerosis. Aim. This paper focuses on the observations made in blood and arteries of patients with atherosclerosis. In principal, flow cytometric analyses show that circulating myeloid (m) and plasmacytoid (p) DCs are diminished in coronary artery disease, while immunohistochemical studies describe increased intimal DC counts with evolving plaque stages. Moreover, mDCs and pDCs appear to behave differently in atherosclerosis. Yet, the origin of plaque DCs and their relationship with blood DCs are unknown. Therefore, several explanations for the observed changes are postulated. In addition, the technical challenges and discrepancies in the research field are discussed. Future. Future studies in humans, in combination with experimental animal studies will unravel mechanisms leading to altered blood and plaque DCs in atherosclerosis. As DCs are crucial for inducing but also dampening immune responses, understanding their life cycle, trafficking and function in atherosclerosis will determine potential use of DCs in antiatherogenic therapies.

Tumor necrosis factor superfamily molecules in acute coronary syndromes

Accumulating evidence suggests that inflammatory pathways play an essential role in all stages of atherogenesis. Inflammatory processes are not only involved in plaque progression, but seem also to play a critical role in plaque rupture. Members of the tumor necrosis factor (TNF) superfamiliy are potent regulators of inflammation and cell survival and consist of 20 ligands that signal through 29 different receptors. Several lines of evidence suggest that TNF-related molecules are involved in the development of acute coronary syndromes (ACS). Most, convincing evidence exists for CD40 ligand-CD40 interaction, but several other members of the TNF superfamily seem also to be involved in this immune-mediated promotion of plaque instability, including LIGHT, receptor activator of nuclear factor κB ligand, and TNF-α. These plaque destabilization pathways involve the bidirectional interaction between platelets and endothelial cells/monocytes, activation of vascular smooth muscle cells, and co-stimulatory effects on T cells, promoting inflammation, thrombus formation, matrix degradation, and apoptosis. TNF-related pathways could contribute to the non-resolving inflammation that characterizes atherosclerosis, representing pathogenic loops that are operating during plaque rupture and the development of ACS. These TNF-related molecules could also represent attractive new targets for therapy in this disorder.

Dendritic cells and their role in atherogenesis

Dendritic cells (DCs) are the most potent professional antigen-presenting cells with the unique ability of primary immune response initiation. DCs originate from bone marrow progenitors, which circulate in the peripheral blood and subsequently penetrate peripheral tissues, where they give rise to immature DCs. In peripheral tissues, DCs continuously monitor the microenvironment and, when the cells encounter 'danger' signals, DCs undergo differentiation and maturation. Maturing DCs usually migrate to lymphatic tissues, where they form contacts with T cells to initiate a primary immune response. DCs were identified in arteries in 1995 and since then, further knowledge has been gained about the peculiarities of vascular-associated DCs and their role in atherosclerosis. Immune reactions toward modified lipoproteins and other factors ignited by resident vascular DCs as well as by newly arrived DCs, which originate from blood monocytes, are believed to destabilize arterial homeostasis from very earlier stages of atherogenesis. There is a remarkable heterogeneity of DCs in atherosclerotic lesions. Some DCs mature and become capable of forming clusters with T cells directly within the arterial wall. The predictive value of the numbers of circulating DC precursors in coronary artery disease and in atherosclerosis has been assessed, and it has been shown that DCs have a role in plaque destabilization. Over recent decades, DCs have proven to be a valuable instrument in immunotherapy approaches against cancer and various autoimmune diseases, and this explains the demand that the accumulated knowledge be applied to the field of atherosclerosis immunotherapy.

Changes in blood dendritic cell counts in relation to type of coronary artery disease and brachial endothelial cell function

BACKGROUND

Recently we reported a decline of circulating myeloid (m) and plasmacytoid (p) dendritic cells (DCs) in patients with coronary artery disease (CAD). This study also determined the total blood DC numbers and focused on effects of extent (one vs. three-vessel disease) and type (stable vs. unstable) of CAD, and on endothelial cell function.

METHODS

Patients undergoing diagnostic coronarography were enrolled in four groups: control patients (atypical chest pain, <50% narrowing, n=15), stable one-vessel (n=15), stable three-vessel (n=15), and unstable one-vessel CAD (n=16). Total blood DCs were identified as lineage (lin) and HLADR, and DC subtypes with blood DC antigen (BDCA)-1 for mDCs and BDCA-2 for pDCs. Flow-mediated dilatation (FMD) was measured in the brachial artery.

RESULTS

Numbers of total blood DCs, mDCs and pDCs declined in CAD patients compared with control patients, but without differences between the CAD groups. Interleukin-6 and high sensitivity C-reactive protein displayed inverse associations with mDCs. A FMD below the median of the study population, use of beta-blockers or of lipid-lowering drugs was associated with increased mDCs, whereas pDCs were similar. Interestingly, the effects of drugs and FMD were additive with that of CAD.

CONCLUSION

This study indicates that lower blood DCs do not result from medication intake or endothelial dysfunction, and are an overall systemic effect of atherosclerosis rather than CAD type (stable or unstable) or number of stenotic coronary arteries. In view of discrete associations with cytokines, FMD, beta-blockers and statins, mDCs and pDCs seem to behave differently and may influence inflammation during atherosclerosis in different ways.

Enhanced TLR4 endothelial cell immunohistochemical expression in symptomatic carotid atherosclerotic plaques

BACKGROUND AND PURPOSE

Toll-like receptor-4 (TLR4) has been linked to the pathogenesis of atherosclerosis. Carotid atheroma endothelial cells (ECs) express TLR4, nevertheless correlations with cerebrovascular symptomatology, epidemiological and clinical variables remain unresolved.

METHODS

Carotid atherosclerotic plaques were obtained by standard carotid endarterectomy from 157 patients with carotid artery disease (84 asymptomatic - Group A, 73 symptomatic - Group B). TLR4 expression was detected by immunohistochemistry and TLR4 positivity, overexpression and intensity of immunostaining in ECs were correlated with cerebrovascular symptomatology, epidemiological and clinical variables.

RESULTS

A significant association was found between TLR4 positivity in ECs and the occurrence of any cerebrovascular event (overall response (OR): 2.85, 95% CI 1.33 - 6.11, p = 0.009). TLR4 overexpression and staining intensity in ECs were both significantly enhanced in symptomatic patients (p < 0.0001 and p = 0.003, respectively). These associations were stronger for the occurrence of a major cerebrovascular accident (CVA) compared with a transient ischemic attack (TIA) or amaurosis fugax. TLR4 expression in ECs was less prominent in statin users (OR: 0.25, 95%CI 0.1 - 0.58, p = 0.001], while it was enhanced in restenotic plaques compared with primary atherosclerotic lesions (p = 0.012).

CONCLUSIONS

TLR4 expression in ECs of carotid atheroma was enhanced in symptomatic patients with most commonly 'unstable' - 'more prone to rupture' carotid plaques.

Toll like receptor 4 in atherosclerosis and plaque destabilization

The immune system plays a pivotal role in initiation and progression of atherosclerosis. Monocytes and T-lymphocytes are the first cells to enter the damaged endothelium. Differentiation of monocytes into macrophages and ingestion of lipids by these macrophages turning them into foam cells is a crucial step in the development of a fatty streak, the first sign of atherosclerosis. In recent years there has been accumulating evidence for the involvement of Toll like receptor 4, a pattern recognition receptor of the innate immune system, in the pathogenesis of atherosclerosis. Different cell types present in the atherosclerotic plaque express TLR4 and several pro-atherogenic ligands have been shown to activate TLR4. The innate immune system and the TLR signaling cascade may play an important role not only in the pathogenesis of atherosclerosis, but also in plaque destabilization. In this review, we discuss the role of TLR4 in the pathogenesis of atherosclerosis and vulnerable plaque development.

Dendritic cells in atherosclerotic disease

Atherosclerosis has been considered a syndrome of dysregulated lipid storage until recent evidence has emphasized the critical contribution of the immune system. Dendritic cells (DC) are positioned at the interface of the innate and adaptive immune system. Recognition of danger signals in atheromas leads to DC activation. Activated DC regulate effector T cells which can kill plaque-resident cells and damage the plaque structure. Two types of DC have been identified in atherosclerotic lesions; classical myeloid DC (mDC) which mainly recognize bacterial signatures and plasmacytoid DC (pDC) which specialize in sensing viral fragments and have the unique potential of producing large amounts of type I interferon (IFN). In human atheromas, type I IFN upregulates expression of the cytotoxic molecule TRAIL which leads to apoptosis of plaque-resident cells. This review will elucidate the role of DC in atherogenesis and particularly in plaque rupture, the underlying pathophysiologic cause of myocardial infarction.

Immune system and atherosclerotic disease: heterogeneity of leukocyte subsets participating in the pathogenesis of atherosclerosis

Atherosclerosis is an inflammatory disease in which a systemic inflammatory reaction is combined with an accumulation of immune cells, such as monocytes/macrophages, dendritic cells (DCs), and numerous lymphocytes, in atherosclerotic plaques. The immune system, comprising innate immunity and adaptive immunity, has been implicated in all stages of atherosclerosis, from initiation through progression and in atherothrombotic complications. It is clear that different subpopulations of leukocytes are involved in the pathogenesis of atherosclerosis and plaque instability. Recent studies have also demonstrated that each heterogeneity of immune-associated cells contributes to the atherogenic and atheroprotective axis. This review highlights recent advances in research and explores the role of the complex heterogeneity of leukocyte subsets, especially monocytes/macrophages (inflammatory monocytes, resident monocytes, M1, and M2), DCs (myeloid DCs, plasmacytoid DCs, pre DCs, conventional DCs, inflammatory DCs), and CD4(+) cells (T-helper 1, T-helper 2, regulatory T, and T-helper 17 cells), in the initiation and development of atherosclerotic disease and its complications.