Role of Toll-like receptor 4 in the initiation and progression of atherosclerotic disease

Mast cell-mediated immune regulation in health and disease

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

Clinical Evidence on the Potential Beneficial Effects of Probiotics and Prebiotics in Cardiovascular Disease

The 'gut microbiome'-the hundreds of trillions of bacteria in the human gastrointestinal tract-serves several functions. The gut microbiome includes all the microorganisms, bacteria, viruses, protozoa, and fungi in the gastrointestinal tract and their genetic material. It helps digest indigestible foods and produces nutrients. Through the metabolism of sugars and proteins, it helps the intestinal barrier, the immune system, and metabolism. Some bacteria, such as those in the gut microbiome, cause disease, but others are essential to our health. These "good" microbes protect us from pathogens. Numerous studies have linked an unhealthy gut microbiome to obesity, insulin resistance, depression, and cardiometabolic risk factors. To maximize probiotic benefits in each case, knowledge of probiotic bacterial strains and how to consume them should be increased. This study aims to examine the benefits of probiotic and prebiotic organisms on cardiovascular health, specifically on heart disease, coronary heart disease, stroke, and hypertension. To complete the research, a literature review was conducted by gathering clinical studies and data. The clinical evidence demonstrates the beneficial effect of probiotics and prebiotic microorganisms on the gut microbiome, which has multiple benefits for overall health and especially for cardiovascular diseases.

CircRNA-miRNA interactions in atherogenesis

Atherosclerosis is the major cause of coronary artery disease (CAD) which includes unstable angina, myocardial infarction, and heart failure. The onset of atherogenesis, a process of atherosclerotic lesion formation in the intima of arteries, is driven by lipid accumulation, a vicious cycle of reactive oxygen species (ROS)-induced oxidative stress and inflammatory reactions leading to endothelial cell (EC) dysfunction, vascular smooth muscle cell (VSMC) activation, and foam cell formation which further fuel plaque formation and destabilization. In recent years, there is a surge in the number of publications reporting the involvement of circular RNAs (circRNAs) in the pathogenesis of cardiovascular diseases, cancers, and metabolic syndromes. These studies have advanced our understanding on the biological functions of circRNAs. One of the most common mechanism of action of circRNAs reported is the sponging of microRNAs (miRNAs) by binding to the miRNAs response element (MRE), thereby indirectly increases the transcription of their target messenger RNAs (mRNAs). Individual networks of circRNA-miRNA-mRNA associated with atherogenesis have been extensively reported, however, there is a need to connect these findings for a complete overview. This review aims to provide an update on atherogenesis-related circRNAs and analyze the circRNA-miRNA-mRNA interactions in atherogenesis. The atherogenic mechanisms and clinical relevance of each atherogenesis-related circRNA were systematically discussed for better understanding of the knowledge gap in this area.

Coronary plaque vulnerability in statin-treated patients with elevated LDL-C and hs-CRP: optical coherence tomography study

There have been no previous attempts to assess coronary plaque morphology in statin-treated patients with combined residual cholesterol and inflammatory risk. The aim of this study was to characterize the morphology using optical coherence tomography (OCT) and to investigate the underlying molecular mechanisms. Two hundred seventy statin-treated patients with stable coronary artery disease who underwent OCT imaging prior to elective percutaneous coronary intervention were included in this single-center retrospective analysis. Subjects were stratified into four groups based on low-density lipoprotein cholesterol (LDL-C) and high-sensitivity C-reactive protein (hs-CRP) levels using 70 mg/dl and 2 mg/L as cut-offs, respectively. OCT images of the target lesions were assessed. For a subset of patients, peripheral blood mononuclear cells (PBMC) were isolated, and gene expression was characterized using microarray analysis. Patients with high LDL-C and high hs-CRP demonstrated a higher frequency of lipid-rich plaques (LRP) (91%, P = 0.03) by OCT. LRPs in these patients had a greater maximal lipid arc (186.6 ± 92.5°, P = 0.047). In addition, plaques from patients who did not achieve dual-target were less frequently calcified (P = 0.003). If calcification was present, it was characterized by a lower maximal arc (P = 0.016) and shorter length (P = 0.025). PBMC gene expression analysis demonstrated functional enrichment of toll-like receptors (TLRs) 1-9 to be associated with high LDL-C and hs-CRP. Obstructive coronary lesions in patients on statin therapy with combined residual cholesterol and inflammatory risk demonstrated a higher prevalence of LRP with greater maximal lipid arcs and more frequent spotty calcifications. PBMC from these patients revealed functional enrichment of TLR 1-9.

Biological active ingredients of Astragali Radix and its mechanisms in treating cardiovascular and cerebrovascular diseases

BACKGROUND

With the rising age of the global population, the incidence rate of cardiovascular and cerebrovascular diseases (CCVDs) is increasing, which causes serious public health burden. The efforts for new therapeutic approaches are still being sought since the treatment effects of existing therapies are not quite satisfactory. Chinese traditional medicine proved to be very efficient in the treatment of CCVDs. Well described and established in Chinese medicine, Astragali Radix, has been commonly administered in the prophylaxis and cure of CCVDs for thousands of years.

PURPOSE

This review summarized the action mode and mechanisms of Astragali Radix phytochemicals on CCVDs, hoping to provide valuable information for the future application, development and improvement of Astragali Radix as well as CCVDs treatment.

METHODS

A plenty of literature on biological active ingredients of Astragali Radix used for CCVDs treatment were retrieved from online electronic PubMed and Web of Science databases.

RESULTS

This review highlighted the effects of five main active components in Astragali Radix including astragaloside Ⅳ, cycloastragenol, astragalus polysaccharide, calycosin-7-O-β-d-glucoside, and calycosin on CCVDs. The mechanisms mainly involved anti-oxidative damage, anti-inflammatory, and antiapoptotic through signaling pathways such as PI3K/Akt, Nrf2/HO-1, and TLR4/NF-κB pathway. In addition, the majority active constituents in AR have no obvious toxic side effects.

CONCLUSION

The main active components of Astragali Radix, especially AS-IV, have been extensively summarized. It has been proved that Astragali Radix has obvious therapeutic effects on various CCVDs, including myocardial and cerebral ischemia, hypertension, atherosclerosis, cardiac hypertrophy, chronic heart failure. CAG possesses anti-ischemia activity without toxicity, indicating a worthy of further development. However, high-quality clinical and pharmacokinetic studies are required to validate the current studies.

Intermedin attenuates macrophage phagocytosis via regulation of the long noncoding RNA Dnm3os/miR-27b-3p/SLAMF7 axis in a mouse model of atherosclerosis in diabetes

Atherosclerosis in diabetes is a leading cause of cardiovascular complications. Intermedin (IMD) is a calcitonin peptide that is known to inhibit macrophage phagocytosis in atherosclerosis, but the exact mechanism is unclear. We investigate genes that are differentially expressed in response to IMD in hyperglycemic conditions and determine whether they delay the progression of atherosclerosis. An atherosclerotic and diabetic-murine model was generated in 8-week-old male ApoE-/- mice receiving streptozotocin and a high-fat diet. The mouse model was treated with IMD and the expression levels of NF-κB, Dnm3os, miR-27b-3p, and SLAMF7 were detected in plaque tissue and macrophages cultured with high glucose concentrations. Phagocytosis was determined by oxidized-low-density lipoprotein (Ox-LDL) uptake and the interactions among Dnm3os, SLAMF7 and miR-27b-3p were assessed by dual-luciferase reporter assays. The expression of NF-κB, Dnm3os, and SLAMF7 was enhanced in atherosclerotic plaques but decreased by IMD. The suppression of Dnm3os reduced plaque formation in IMD-treated mice even further whereas increased by miR-27b-3p. Dnm3os and SLAMF7 were competitively bind to miR-27b-3p in vivo. In vitro, ox-LDL uptake is elevated in macrophages cultured in hyperglycemic conditions but reduced by IMD. Dual-luciferase assays indicate that Dnm3os positively regulates SLAMF7 through miR-27b-3p expression. In conclusion, Dnm3os is involved in macrophage phagocytosis through the competitive binding of SLAMF7 with miR-27b-3p. IMD induces the suppression of Dnm3os to inhibit macrophage phagocytosis and alleviate atherosclerosis in diabetes.

Implications for the role of lipopolysaccharide in the development of atherosclerosis

Mounting scientific evidence over decades has established that atherosclerosis is a chronic inflammatory disorder. Among the potentially critical sources of vascular inflammation during atherosclerosis are the components of pathogenic bacteria, especially lipopolysaccharide (LPS). Toll-like receptor (TLR)-4, expressed on different inflammatory cells involved with the recognition of bacterial LPS, has been recognized to have mutations that are prevalent in a number of ethnic groups. Such mutations have been associated with a decreased risk of atherosclerosis. In addition, epidemiological investigations have proposed that LPS confers a risk factor for the development of atherosclerosis. Gram-negative bacteria are the major source of LPS in an individual's serum, which may be generated during subclinical infections. The major cell receptors on inflammatory cells involved in the pathogenesis of atherosclerosis, like macrophages, monocytes, and dendritic cells (DCs), are CD14, MD-2, and LPS binding protein (LBP). These receptors have been blamed for the development of atherosclerosis through dysregulated activation following LPS recognition. Lipoproteins may also play a role in modulating the LPS-induced inflammatory events during atherosclerosis development. In this review article, we attempt to clarify the role of LPS in the initiation and progression of atherosclerotic lesion development.

Age-dependent messenger RNA expression of toll-like receptor 4 and intercellular adhesion molecule-1 in peripheral blood mononuclear cells

BACKGROUND

Inflammation plays an important role in the ageing process in which monocytes/macrophages are important players. Intercellular adhesion molecule-1 (ICAM-1), tumour necrosis factor-α (TNF-α) and Toll-like receptor 4 (TLR4) are well-known inflammatory markers. This study aimed to investigate the relationship between age and the expression and correlation of ICAM-1, TNF-α and TLR4 mRNA in peripheral blood mononuclear cells (PBMCs).

METHODS

A total of 239 participants were recruited in a medical centre in Taiwan. The mRNA isolated from the PBMCs was used to determine the levels of ICAM-1, TNF-α and TLR4 mRNAs with real-time polymerase chain reaction (PCR). The propensity-matched analysis was also applied for subgroup analysis.

RESULTS

When compared 189 older adults (≧65 years) to 50 younger adults (<65 years), the ICAM-1, TNF-α and TLR4 mRNA levels in PBMCs were significantly higher in older adults (2.00 ± 0.72 vs 0.87 ± 0.34 for ICAM-1, 2.32 ± 0.69 vs 1.15 ± 0.44 for TNF-α and 1.56 ± 0.47 vs 1.05 ± 0.51 for TLR4, and all P < .0001). Also, both age and TLR4 were independent factors affecting mononuclear cell ICAM-1 in the multiple linear regression analysis (P < .0001).

CONCLUSION

The mRNA levels of ICAM-1 and TLR4 in PBMCs are higher in older adults than those in younger adults. TLR4 is an independent factor affecting ICAM-1 expression in PBMCs, especially in older adults. This may suggest that ICAM-1 and TLR4 in PBMCs are potential biomarkers and their relationship may shed some light on the ageing process.

Toll-Like Receptor Signaling Pathways: Novel Therapeutic Targets for Cerebrovascular Disorders

Toll-like receptors (TLRs), a class of pattern recognition proteins, play an integral role in the modulation of systemic inflammatory responses. Cerebrovascular diseases (CVDs) are a group of pathological conditions that temporarily or permanently affect the brain tissue mostly via the decrease of oxygen and glucose supply. TLRs have a critical role in the activation of inflammatory cascades following hypoxic-ischemic events and subsequently contribute to neuroprotective or detrimental effects of CVD-induced neuroinflammation. The TLR signaling pathway and downstream cascades trigger immune responses via the production and release of various inflammatory mediators. The present review describes the modulatory role of the TLR signaling pathway in the inflammatory responses developed following various CVDs and discusses the potential benefits of the modulation of different TLRs in the improvement of functional outcomes after brain ischemia.

Effect of probiotic supplementation along with calorie restriction on metabolic endotoxemia, and inflammation markers in coronary artery disease patients: a double blind placebo controlled randomized clinical trial

Purpose

Alterations in the gut microbiome (dysbiosis) has been associated with increased microbial translocation, leading to chronic inflammation in coronary artery disease (CAD). It has been proposed that modulation of gut microbiota by probiotic might modify metabolic endotoxemia. Therefore, the purpose of this study was to examine the effects of Lactobacillus rhamnosus GG (LGG) on endotoxin level, and biomarkers of inflammation in CAD participants.

Methods

This study was a 12-weeks randomized, double-blind, and intervention on 44 patients with CAD. Patients were randomly allocated to receive either one LGG capsule 1.6 × 10⁹ colony-forming unit (CFU) or the placebo capsules for 12 weeks. In addition, all the participants were also prescribed a calorie-restricted diet. Serum levels of interleukin-1β (IL-1β), Toll-like receptor 4 (TLR4), interleukin-10 (IL-10), and lipopolysaccharide (LPS), were assessed before and after the intervention.

Results

A significant decrease in IL1-Beta concentration (− 1.88 ± 2.25, vs. 0.50 ± 1.58 mmol/L, P = 0.027), and LPS levels (− 5.88 ± 2.70 vs. 2.96+ 5.27 mg/L, P = 0.016), was observed after the probiotic supplementation compared with the placebo. Participants who had ≥2.5 kg weight loss showed significantly improved cardiovascular-related factors, compared to patients with < 2.5 kg weight reduction, regardless of the supplement they took.

Conclusion

These data provide preliminary evidence that probiotic supplementation has beneficial effects on metabolic endotoxemia, and mega inflammation in participants with CAD.

Reshaping of the gastrointestinal microbiome alters atherosclerotic plaque inflammation resolution in mice

Since alterations in the intestinal microbiota may induce systemic inflammation and polarization of macrophages to the M1 state, the microbiome role in atherosclerosis, an M1-driven disease, requires evaluation. We aimed to determine if antibiotic (Abx) induced alterations to the intestinal microbiota interferes with atherosclerotic plaque inflammation resolution after lipid-lowering in mice. Hyperlipidemic Apoe^−/− mice were fed a western diet to develop aortic atherosclerosis with aortas then transplanted into normolipidemic wild-type (WT) mice to model clinically aggressive lipid management and promote atherosclerosis inflammation resolution. Gut microbial composition pre and post-transplant was altered via an enteral antibiotic or not. Post aortic transplant, after Abx treatment, while plaque size did not differ, compared to Apoe^−/− mice, Abx^– WT recipient mice had a 32% reduction in CD68-expressing cells (p = 0.02) vs. a non-significant 12% reduction in Abx⁺ WT mice. A trend toward an M1 plaque CD68-expresing cell phenotype was noted in Abx⁺ mice. By 16S rRNA sequence analysis, the Abx⁺ mice had reduced alpha diversity and increased Firmicutes/Bacteroidetes relative abundance ratio with a correlation between gut Firmicutes abundance and plaque CD68-expressing cell content (p < 0.05). These results indicate that in a murine atherosclerotic plaque inflammation resolution model, antibiotic-induced microbiome perturbation may blunt the effectiveness of lipid-lowering to reduce the content of plaque inflammatory CD68-expressing cells.

Knockdown of circ_0003204 alleviates oxidative low-density lipoprotein-induced human umbilical vein endothelial cells injury: Circulating RNAs could explain atherosclerosis disease progression

Atherosclerosis (AS) is a serious cardiovascular disease. Circular RNAs (circRNAs) play an important role in the progression of many diseases, including AS. However, the role of circ_0003204 in AS is not clear. Oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs) were used to construct an AS cell model in vitro. Cell viability was assessed using cell counting kit 8 (CCK8) assay. Flow cytometry and caspase-3 activity were used to measure cell apoptosis. The contents of inflammatory cytokines were measured using enzyme-linked immunosorbent assay (ELISA). Oxidative stress marker expression and cell injury marker activity were detected by their corresponding Assay Kits. Besides, the expression levels of circ_0003204, miR-330-5p, and toll-like receptor 4 (TLR4) were tested by real-time polymerase chain reaction (qPCR). The interaction between miR-330-5p and circ_0003204 or TLR4 was examined by dual-luciferase reporter assay and RNA pull-down assay. Western blot (WB) analysis was used to determine the levels of TLR4 protein and nuclear factor-kappa B (NF-κB) signaling pathway-related protein. Our data suggested that ox-LDL could suppress viability and promote apoptosis, inflammatory response, and oxidative stress in HUVECs. circ_0003204 was highly expressed in ox-LDL-induced HUVECs, and its silencing could inhibit ox-LDL-induced HUVECs injury. miR-330-5p could be sponged by circ_0003204, and its inhibitor could reverse the inhibition effect of silenced circ_0003204 on ox-LDL-induced HUVECs injury. Further, TLR4 could be targeted by miR-330-5p, and its overexpression could invert the suppression effect of miR-330-5p on ox-LDL-induced HUVECs injury. The activity of the NF-κB signaling pathway was regulated by the circ_0003204/miR-330-5p/TLR4 axis. Our results indicated that circ_0003204 silencing could alleviate ox-LDL-induced HUVECs injury, suggesting that circ_0003204 might be a novel target for AS treatment.

The Effect of Statins through Mast Cells in the Pathophysiology of Atherosclerosis: a Review

PURPOSE OF REVIEW

In this review, we discuss the evidence supporting the effects of statins on mast cells (MCs) in atherosclerosis and their molecular mechanism of action.

RECENT FINDINGS

Statins or HMG-CoA reductase inhibitors are known for their lipid-lowering properties and are widely used in the prevention and treatment of cardiovascular diseases. There is growing evidence that statins have an inhibitory effect on MCs, which contributes to the pleiotropic effect of statins in various diseases. MCs are one of the crucial effectors of the immune system which play an essential role in the pathogenesis of multiple disorders. Recent studies have shown that MCs are involved in the development of atherosclerotic plaques. MCs secrete various inflammatory cytokines (IL-6, IL4, TNF-α, and IFNγ) and inflammatory mediators (histamine, tryptase, proteoglycans) after activation by various stimulants. This, in turn, will exacerbate atherosclerosis. Statins suppress the activation of MCs via IgE inhibition which leads to inhibition of inflammatory mediators and cytokines which are involved in the development and progression of atherosclerosis. In keeping with this evidence presented here, MCs can be considered as one of the therapeutic targets for statins in the treatment of atherosclerosis.

Notoginsenoside R1 upregulates miR-221-3p expression to alleviate ox-LDL-induced apoptosis, inflammation, and oxidative stress by inhibiting the TLR4/NF-κB pathway in HUVECs

Atherosclerosis (AS) is a common vascular disease, which can cause apoptosis of vascular endothelial cells. Notoginsenoside R1 (NGR1) is considered an anti-AS drug. MicroRNAs (miRNAs) are believed to play a vital role in cell apoptosis and angiogenesis. This study aimed to explore the mechanism of NGR1 for treating AS through miRNAs. Flow cytometry was used to detect the apoptosis rate. The levels of inflammatory cytokines interleukin (IL)-6 and IL-1β were detected using ELISA. Reactive oxygen species (ROS) and malondialdehyde (MDA) levels were measured using corresponding assay kits. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was performed to detect miR-221-3p expression. Dual-luciferase reporter and RNA immunoprecipitation assays were carried out to examine the relationship between miR-221-3p and toll-like receptors 4 (TLR4). Also, western blot analysis was performed to determine the levels of TLR4 and nuclear factor kappa B (NF-κB) signaling pathway-related proteins. Oxidized low-density lipoprotein (ox-LDL) induced human umbilical vein endothelial cells (HUVECs) apoptosis, inflammation, and oxidative stress. NGR1 alleviated the negative effect of ox-LDL through promoting the expression of miR-221-3p in HUVECs. TLR4 was a target of miR-221-3p, and its overexpression could reverse the inhibition effects of miR-221-3p on apoptosis, inflammation, and oxidative stress. NGR1 improved miR-221-3p expression to inhibit the activation of the TLR4/NF-κB pathway in ox-LDL-treated HUVECs. NGR1 decreased ox-LDL-induced HUVECs apoptosis, inflammation, and oxidative stress through increasing miR-221-3p expression, thereby inhibiting the activation of the TLR4/NF-κB pathway. This study of the mechanism of NGR1 provided a more theoretical basis for the treatment of AS.

The role of Toll-like receptor signaling pathways in cerebrovascular disorders: the impact of spreading depolarization

Cerebral vascular diseases (CVDs) are a group of disorders that affect the blood supply to the brain and lead to the reduction of oxygen and glucose supply to the neurons and the supporting cells. Spreading depolarization (SD), a propagating wave of neuroglial depolarization, occurs in different CVDs. A growing amount of evidence suggests that the inflammatory responses following hypoxic-ischemic insults and after SD plays a double-edged role in brain tissue injury and clinical outcome; a beneficial effect in the acute phase and a destructive role in the late phase. Toll-like receptors (TLRs) play a crucial role in the activation of inflammatory cascades and subsequent neuroprotective or harmful effects after CVDs and SD. Here, we review current data regarding the pathophysiological role of TLR signaling pathways in different CVDs and discuss the role of SD in the potentiation of the inflammatory cascade in CVDs through the modulation of TLRs.

New insights into the role of iron in inflammation and atherosclerosis

Iron is fundamental for life-essential processes. However, it can also cause oxidative damage, which is thought to trigger numerous pathologies, including cardiovascular diseases. The role of iron in the pathogenesis of atherosclerosis is still not completely understood. Macrophages are both key players in the handling of iron throughout the body and in the onset, progression and destabilization of atherosclerotic plaques. Iron itself might impact atherosclerosis through its effects on macrophages. However, while targeting iron metabolism within macrophages may have some beneficial effects on preventing atherosclerotic plaque progression there may also be negative consequences. Thus, the prevailing view of iron being capable of accelerating the progression of coronary disease through lipid peroxidation may not fully take into account the multi-faceted role of iron in pathogenesis of atherosclerosis. In this review, we will summarize the current understanding of iron metabolism in the context of the complex interplay between iron, inflammation, and atherosclerosis.

MiR-590 Inhibits Endothelial Cell Apoptosis by Inactivating the TLR4/NF-κB Pathway in Atherosclerosis

PURPOSE

Previous study has well documented the anti-apoptotic effects of miR-590 on oxidized low-density lipoprotein (ox-LDL)-treated endothelial cells (ECs). However, the mechanism underlying the anti-apoptotic effects of miR-590 in ox-LDL-treated ECs remains to be further addressed.

MATERIALS AND METHODS

ApoE^-/- mice fed with a high-fat diet (HFD) and human aortic endothelial cells (HAECs) treated with ox-LDL were used as in vivo and in vitro models of atherosclerosis. The expressions of miR-590 and toll-like receptor 4 (TLR4) were detected by quantitative real-time PCR and Western blot, respectively. Atherosclerotic lesion analysis was performed using Evans blue and hematoxylin-eosin staining. Cell proliferation was assessed by MTT assay. Apoptosis was examined using flow cytometry analysis and Western blot analysis of Cleaved poly (ADP-ribose) polymerase (PARP) and Cleaved Caspase-3 levels. The effect of miR-590 on TLR4/nuclear factor kappa B (NF-κB) pathway was evaluated by Western blot. Binding between miR-590 and TLR4 was confirmed by luciferase reporter assay and Western blot.

RESULTS

miR-590 was downregulated in the aorta tissues from HFD-fed apoE^-/- mice and ox-LDL-treated HAECs. miR-590 overexpression inhibited atherosclerotic lesion in HFD-induced apoE^-/- mice and promoted proliferation and inhibited apoptosis of ox-LDL-treated HAECs. Additionally, TLR4 was identified as a direct target of miR-590 in ox-LDL-treated HAECs. Moreover, anti-miR-590 reversed TLR4 knockdown-mediated promotion of cell proliferation and suppression of apoptosis in ox-LDL-treated HAECs. miR-590 overexpression suppressed the TLR4/NF-κB pathway, and inhibition of the TLR4/NF-κB pathway promoted cell proliferation and impeded apoptosis in ox-LDL-treated HAECs.

CONCLUSION

miR-590 promoted proliferation and blocked ox-LDL-induced apoptosis in HAECs through inhibition of the TLR4/NF-κB pathway.

MiR-370 inhibits vascular inflammation and oxidative stress triggered by oxidized low-density lipoprotein through targeting TLR4

Atherosclerosis, as a chronic cardiovascular disease, still remains a serious threat to human health. Inflammation and oxidative stress are commonly involved in various stages of atherosclerosis development. MicroRNAs are reported to play important roles in macrophages, which can respond to inflammation and oxidative stress. In our current study, we focused on the biological roles of miR-370 in atherosclerosis. According to the previously research, miR-370 was downregulated in AS mice models. Oxidized low-density lipoprotein (Ox-LDL) is regarded as a crucial regulator of atherosclerosis and we observed that miR-370 was decreased by ox-LDL dose-dependently and time-dependently in THP-1 cells. Then, it was found that miR-370 overexpression was able to inhibit inflammation molecules including IL-6 and IL-1β. Meanwhile, ROS levels, and malondialdehyde (MDA) were also restrained by miR-370 mimics in vitro. Toll-like receptor 4 (TLR4) has been implicated in many inflammation diseases. It can serve as a target of miR-370 and TLR4 expression was greatly increased in ox-LDL-incubated THP-1 cells in a time and dose dependent manner. The negative correlation was validated using a dual-luciferase reporter assay in our study. In conclusion, our present study revealed that miR-370 can reduce inflammatory reaction and inhibit the ROS production by targeting TLR4 in THP-1 cells.

Association between Toll-like receptor 4 Asp299Gly polymorphism and coronary heart disease susceptibility

Published data on the association between Toll-like receptor 4 (TLR4) Asp299Gly polymorphism and coronary heart disease (CHD) susceptibility are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. English-language studies were identified by searching PubMed and Embase databases (up to November 2016). All epidemiological studies were regarding Caucasians because no TLR4 Asp/Gly and Gly/Gly genotypes have been detected in Asians. A total of 20 case-control studies involving 14,416 cases and 10,764 controls were included in the meta-analysis. Overall, no significant associations were found between TLR4 Asp299Gly polymorphism and CHD susceptibility in the dominant model (OR=0.89; 95%CI=0.74 to 1.06; P=0.20) pooled in the meta-analysis. In the subgroup analysis by CHD, non-significant associations were found in cases compared to controls. When stratified by control source, no significantly decreased risk was found in the additive model or dominant model. The present meta-analysis suggests that the TLR4 Asp299Gly polymorphism was not associated with decreased CHD risk in Caucasians.

The role of iron in the pathogenesis of atherosclerosis

Ferritin and increased iron stores first appeared on the list of cardiovascular risk factors more than 30 years ago and their causal role in the pathogenesis of atherosclerosis has been heavily discussed since the early 1990s. It seems that besides traditional factors such as hyperlipoproteinemia, hypertension, diabetes mellitus, obesity, physical inactivity, smoking and family history, high iron stores represent an additional parameter that could modify individual cardiovascular risk. The role of iron in the pathogenesis of atherosclerosis was originally primarily associated with its ability to catalyze the formation of highly reactive free oxygen radicals and the oxidation of atherogenic lipoproteins. Later, it became clear that the mechanism is more complex. Atherosclerosis is a chronic fibroproliferative inflammatory process and iron, through increased oxidation stress as well as directly, can control both native and adaptive immune responses. Within the arterial wall, iron affects all of the cell types that participate in the atherosclerotic process (monocytes/macrophages, endothelial cells, vascular smooth muscle cells and platelets). Most intracellular iron is bound in ferritin, whereas redox-active iron forms labile iron pool. Pro-inflammatory and anti-inflammatory macrophages within arterial plaque differ with regard to the amount of intracellular iron and most probably with regard to their labile iron pool. Yet, the relation between plasma ferritin and intracellular labile iron pool has not been fully clarified. Data from population studies document that the consumption of meat and lack of physical activity contribute to increased iron stores. Patients with hereditary hemochromatosis, despite extreme iron storage, do not show increased manifestation of atherosclerosis probably due to the low expression of hepcidin in macrophages.

DC-SIGN and Toll-like receptor 4 mediate oxidized low-density lipoprotein-induced inflammatory responses in macrophages

The regulation of inflammatory responses by innate immune receptors is recognized as a crucial step in the development of atherosclerosis, although the precise molecular mechanisms remain to be elucidated. This study focused on illustrating the roles of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN)- and Toll-like receptor 4 (TLR4)-regulated inflammatory responses in macrophages. We found that DC-SIGN expression levels were increased in macrophages of atherosclerotic plaques. Oxidized low-density lipoprotein (oxLDL) significantly enhanced DC-SIGN protein expression levels after a short-term exposure. Knockdown of DC-SIGN decreased expression and secretion of interleukin 1-β (IL1-β), monocyte chemo-attractant protein 1 (MCP-1), tumor necrosis factor-α (TNFα) and matrix metalloproteinase-9 (MMP-9). Immunofluorescence studies demonstrated that DC-SIGN and TLR4 co-localized in regions of the plaques. Moreover, DC-SIGN was co-expressed with TLR4 on the plasma membrane after oxLDL stimulation. The presence of an endogenous interaction and the results of the in vitro pull-down assays revealed that DC-SIGN binds directly with TLR4. We also present evidence that DC-SIGN mediates TLR4-regulated NFκB activation but not activation of p38 and JNK. Our results suggest an essential role of DC-SIGN/TLR4 signaling in macrophages in the pathogenesis of atherosclerosis.

Hypaphorine Attenuates Lipopolysaccharide-Induced Endothelial Inflammation via Regulation of TLR4 and PPAR-γ Dependent on PI3K/Akt/mTOR Signal Pathway

Endothelial lesion response to injurious stimuli is a necessary step for initiating inflammatory cascades in blood vessels. Hypaphorine (Hy) from different marine sources is shown to exhibit anti-inflammatory properties. However, the potential roles and possible molecular mechanisms of Hy in endothelial inflammation have yet to be fully clarified. We showed that Hy significantly inhibited the positive effects of lipopolysaccharide (LPS) on pro-inflammatory cytokines expressions, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), monocyte chemoattractant protein 1 (MCP-1) and vascular cellular adhesion molecule-1 (VCAM-1), as well as induction of the phosphorylation of Akt and mTOR in HMEC-1 cells. The downregulated peroxisome proliferator-activated receptor γ (PPAR-γ) and upregulated toll-like receptor 4 (TLR4) expressions in LPS-challenged endothelial cells were prevented by Hy. Inhibition of both PI3K and mTOR reversed LPS-stimulated increases in TLR4 expressions and decreases in PPAR-γ levels. Genetic silencing of TLR4 or PPAR-γ agonist pioglitazone obviously abrogated the levels of pro-inflammatory cytokines in LPS-treated HMEC-1 cells. These results suggest that Hy may exert anti-inflammatory actions through the regulation of TLR4 and PPAR-γ dependent on PI3K/Akt/mTOR signal pathways. Hy may be considered as a therapeutic agent that can potentially relieve or ameliorate endothelial inflammation-associated diseases.

Toll-like Receptors in the Vascular System: Sensing the Dangers Within

Toll-like receptors (TLRs) are components of the innate immune system that respond to exogenous infectious ligands (pathogen-associated molecular patterns, PAMPs) and endogenous molecules that are released during host tissue injury/death (damage-associated molecular patterns, DAMPs). Interaction of TLRs with their ligands leads to activation of downstream signaling pathways that induce an immune response by producing inflammatory cytokines, type I interferons (IFN), and other inflammatory mediators. TLR activation affects vascular function and remodeling, and these molecular events prime antigen-specific adaptive immune responses. Despite the presence of TLRs in vascular cells, the exact mechanisms whereby TLR signaling affects the function of vascular tissues are largely unknown. Cardiovascular diseases are considered chronic inflammatory conditions, and accumulating data show that TLRs and the innate immune system play a determinant role in the initiation and development of cardiovascular diseases. This evidence unfolds a possibility that targeting TLRs and the innate immune system may be a novel therapeutic goal for these conditions. TLR inhibitors and agonists are already in clinical trials for inflammatory conditions such as asthma, cancer, and autoimmune diseases, but their study in the context of cardiovascular diseases is in its infancy. In this article, we review the current knowledge of TLR signaling in the cardiovascular system with an emphasis on atherosclerosis, hypertension, and cerebrovascular injury. Furthermore, we address the therapeutic potential of TLR as pharmacological targets in cardiovascular disease and consider intriguing research questions for future study.

Elaidate, an 18-carbon trans-monoenoic fatty acid, but not physiological fatty acids increases intracellular Zn(2+) in human macrophages

Artificial trans fatty acids promote atherosclerosis by blocking macrophage clearance of cell debris. Classical fatty-acid response mechanisms include TLR4-NF-κB activation, and Erk1/2 phosphorylation, but these may not indicate long-term mechanisms. Indeed, nuclear NF-κB was increased by 60 min treatment by 30 μM of the 18 carbon trans unsaturated fatty acid elaidic acid (elaidate), the physiological cis-unsaturated fatty acid oleic acid (oleate), and the 18 or 16 carbon saturated fatty acids stearic and palmitic acid (stearate or palmitate). However, except for stearate, effects on related pathways were minimal at 44 h. To determine longer term effects of trans fatty acids, we compared mRNA expression profiles of (trans) elaidate to (cis) oleate, 30 μM, at 44 h in human macrophages. We found that elaidate changed Zn(2+) -homeostasis gene mRNAs markedly. This might be important because Zn(2+) is a major regulator of macrophage activity. Messenger RNAs of seven Zn(2+) -binding metallothioneins decreased 2-4-fold; the zinc importer SLC39A10 increased twofold, in elaidate relative to oleate-treated cells. Results were followed by quantitative PCR comparing cis, trans, and saturated fatty acid effects on Zn(2+) -homeostasis gene mRNAs. This confirmed that elaidate uniquely decreased metallothionein expression and increased SLC39A10 at 44 h. Further, intracellular Zn(2+) was measured using N-(carboxymethyl)-N-[2-[2-[2(carboxymethyl) amino]-5-(2,7,-difluoro-6-hydroxy-3-oxo-3H-xanthen-9-yl)-phenoxy]-ethoxy]-4-methoxyphenyl]glycine, acetoxymethyl ester (FluoZin-3-AM). This showed that, at 44 h, only cells treated with elaidate had increased Zn(2+) . The durable effect of elaidate on Zn(2+) activation is a novel and specific effect of trans fatty acids on peripheral macrophage metabolism.

Repulsive guidance molecule a blockade exerts the immunoregulatory function in DCs stimulated with ABP and LPS

Repulsive guidance molecule a (RGMa) is an axonal guidance molecule that has recently found to exert function in immune system. This study evaluated the function of RGMa in modulation of dendritic cells (DCs) function stimulated with Achyranthes bidentata polysaccharide (ABP) and lipopolysaccharide (LPS) using a RGMa-neutralizing antibody. Compared with the Control-IgG/ABP and Control-IgG/LPS groups, DCs in the Anti-RGMa/ABP and Anti-RGMa/LPS groups 1) showed small, round cells with a few cell processes and organelles, and many pinocytotic vesicles; 2) had decreased MHC II, CD86, CD80, and CD40 expression; 3) displayed the decreased IL-12p70, IL-1β and TNF-α levels and increased IL-10 secretion; 4) had a high percentage of FITC-dextran uptake; and 5) displayed a reduced ability to drive T cell proliferation and reinforced T cell polarization toward a Th2 cytokine pattern. We conclude that DCs treated with RGMa-neutralizing antibodies present with tolerogenic and immunoregulatory characteristics, which provides new insights into further understanding of the function of RGMa.

Regulatory T cells in atherosclerosis: critical immune regulatory function and therapeutic potential

Atherosclerosis is a chronic inflammatory disease that is mediated by innate and adaptive immune responses. The disease is characterized by sub-endothelial accumulation and modification of lipids in the artery wall triggering an inflammatory reaction which promotes lesion progression and eventual plaque rupture, thrombus formation, and the respective clinical sequelae such as myocardial infarction or stroke. During the past decade, T-cell-mediated immune responses, especially control of pro-inflammatory signals by regulatory T cells (Tregs), have increasingly attracted the interest of experimental and clinical researchers. By suppression of T cell proliferation and secretion of anti-inflammatory cytokines, such as interleukin-10 (IL-10) and transforming growth factor-β, Tregs exert their atheroprotective properties. Atherosclerosis-prone, hyperlipidemic mice harbor systemically less Tregs compared to wild-type mice, suggesting an imbalance of immune cells which affects local and systemic inflammatory and potentially metabolic processes leading to atherogenesis. Restoring or increasing Treg frequency and enhancing their suppressive capacity by various modulations may pose a promising approach for treating inflammatory conditions such as cardiovascular diseases. In this review, we briefly summarize the immunological basics of atherosclerosis and introduce the role and contribution of different subsets of T cells. We then discuss experimental data and current knowledge pertaining to Tregs in atherosclerosis and perspectives on manipulating the adaptive immune system to alleviate atherosclerosis and cardiovascular disease.

Toll-like receptors mediating vascular malfunction: Lessons from receptor subtypes

Toll-like receptors (TLR) are a subfamily of pattern recognition receptors (PRR) implicated in a variety of vascular abnormalities. However, the pathophysiological role and the interplay between different TLR-mediated innate and adaptive immune responses during the development of vascular diseases remain largely unspecified. TLR are widely distributed in both immune and nonimmune cells in the blood vessel wall. The expressions and locations of TLR are dynamically regulated in response to distinct molecular patterns derived from pathogens or damaged host cells. As a result, the outcome of TLR signaling is agonist- and cell type-dependent. A better understanding of discrete TLR signaling pathways in the vasculature will provide unprecedented opportunities for the discovery of novel therapies in many inflammatory vascular diseases. The present brief review discusses the role of individual TLR in controlling cellular functions of the vascular system, by focusing on the inflammatory responses within the blood vessel wall which contribute to the development of hypertension and atherosclerosis.

Cigarette Smoke Amplifies Inflammatory Response and Atherosclerosis Progression Through Activation of the H1R-TLR2/4-COX2 Axis

Emerging evidence suggests that infection and persistent inflammation are key players in the pathogenesis of atherosclerotic cardiovascular disease (CVD). Although it is well established that cigarette smoke (CS) promotes atherosclerotic CVD, very little is known about the potential impact of the collective effects of CS and intermittent or chronic subclinical infection on atherosclerosis. Our previous studies demonstrated that mast cell-derived histamine and lipopolysaccharide (LPS) synergistically enhance endothelial cell inflammatory response. We further noted that the synergy between histamine and LPS was due to reciprocal upregulation of histamine receptor and Toll-like receptor 4 (TLR4) expression and functions. These results suggest that the combined and persistent effects of mast cell mediators and bacterial agents on the vasculature are risk factors of CVD. Our recent data demonstrated that CS extract enhances histamine- and LPS-induced expression of cyclooxygenase-2 (COX-2) in endothelial cells, suggesting that CS and mast cell mediators may collectively amplify inflammatory response in the vessel wall. We hypothesize that CS enhances histamine-mediated upregulation of TLR2/TLR4 signaling in the endothelium and promotes progression of atherosclerosis. This article presents our perspective on the modulatory effects of CS and nicotine on the “histamine-TLR-COX-2 axis.”

miR-223 Inhibits Lipid Deposition and Inflammation by Suppressing Toll-Like Receptor 4 Signaling in Macrophages

Atherosclerosis and its complications rank as the leading cause of death with the hallmarks of lipid deposition and inflammatory response. MicroRNAs (miRNAs) have recently garnered increasing interests in cardiovascular disease. In this study, we investigated the function of miR-223 and the underlying mechanism in atherosclerosis. In the atherosclerotic ApoE^−/− mice models, an obvious increase of miR-223 was observed in aortic atherosclerotic lesions. In lipopolysaccharide (LPS) activated macrophages, its expression was decreased. The miR-223 overexpression significantly attenuated macrophage foam cell formation, lipid accumulation and pro-inflammatory cytokine production, which were reversed by anti-miR-223 inhibitor transfection. Mechanism assay corroborated that miR-223 negatively regulated the activation of the toll-like receptor 4 (TLR4)-nuclear factor-κB (NF-κB) pathway. Pretreatment with a specific inhibitor of NF-κB (pyrrolidinedithiocarbamate, PDTC) strikingly abrogated miR-223 silence-induced lipid deposition and inflammatory cytokine production. Furthermore, PI3K/AKT was activated by miR-223 up-regulation. Pretreatment with PI3K/AKT inhibitor LY294002 strikingly ameliorated the inhibitory effects of miR-223 on the activation of TLR4 and p65, concomitant with the increase in lipid deposition and inflammatory cytokine production. Together, these data indicate that miR-223 up-regulation might abrogate the development of atherosclerosis by blocking TLR4 signaling through activation of the PI3K/AKT pathway, and provides a promising therapeutic avenue for the treatment of atherosclerosis.

Relation between TLR4/NF-κB signaling pathway activation by 27-hydroxycholesterol and 4-hydroxynonenal, and atherosclerotic plaque instability

It is now thought that atherosclerosis, although due to increased plasma lipids, is mainly the consequence of a complicated inflammatory process, with immune responses at the different stages of plaque development. Increasing evidence points to a significant role of Toll-like receptor 4 (TLR4), a key player in innate immunity, in the pathogenesis of atherosclerosis. This study aimed to determine the effects on TLR4 activation of two reactive oxidized lipids carried by oxidized low-density lipoproteins, the oxysterol 27-hydroxycholesterol (27-OH) and the aldehyde 4-hydroxynonenal (HNE), both of which accumulate in atherosclerotic plaques and play a key role in the pathogenesis of atherosclerosis. Secondarily, it examined their potential involvement in mediating inflammation and extracellular matrix degradation, the hallmarks of high-risk atherosclerotic unstable plaques. In human promonocytic U937 cells, both 27-OH and HNE were found to enhance cell release of IL-8, IL-1β, and TNF-α and to upregulate matrix metalloproteinase-9 (MMP-9) via TLR4/NF-κB-dependent pathway; these actions may sustain the inflammatory response and matrix degradation that lead to atherosclerotic plaque instability and to their rupture. Using specific antibodies, it was also demonstrated that these inflammatory cytokines increase MMP-9 upregulation, thus enhancing the release of this matrix-degrading enzyme by macrophage cells and contributing to plaque instability. These innovative results suggest that, by accumulating in atherosclerotic plaques, the two oxidized lipids may contribute to plaque instability and rupture. They appear to do so by sustaining the release of inflammatory molecules and MMP-9 by inflammatory and immune cells, for example, macrophages, through activation of TLR4 and its NF-κB downstream signaling.

L-4F inhibits lipopolysaccharide-mediated activation of primary human neutrophils

Human apolipoprotein A-I (apoA-I) mimetic L-4F inhibits acute inflammation in endotoxemic animals. Since neutrophils play a crucial role in septic inflammation, we examined the effects of L-4F, compared to apoA-I, on lipopolysaccharide (LPS)-mediated activation of human neutrophils. We performed bioassays in human blood, isolated human neutrophils (incubated in 50 % donor plasma), and isolated human leukocytes (incubated in 5 and 50 % plasma) in vitro. In whole blood, both L-4F and apoA-I inhibited LPS-mediated elevation of TNF-α and IL-6. In LPS-stimulated neutrophils, L-4F and apoA-I (40 μg/ml) also decreased myeloperoxidase and TNF-α levels; however, L-4F tended to be superior in inhibiting LPS-mediated increase in IL-6 levels, membrane lipid rafts abundance and CD11b expression. In parallel experiments, when TNF-α and IL-8, instead of LPS, was used for cell stimulation, L-4F and/or apoA-I revealed only limited efficacy. In LPS-stimulated leukocytes, L-4F was as effective as apoA-I in reducing superoxide formation in 50 % donor plasma, and more effective in 5 % donor plasma (P<0.05). Limulus ambocyte lysate (LAL) and surface plasmon resonance assays showed that L-4F neutralizes LAL endotoxin activity more effectively than apoA-I (P<0.05) likely due to avid binding to LPS. We conclude that (1) direct binding/neutralization of LPS is a major mechanism of L-4F in vitro; (2) while L-4F has similar efficacy to apoA-I in anti-endotoxin effects in whole blood, it demonstrates superior efficacy to apoA-I in aqueous solutions and fluids with limited plasma components. This study rationalizes the utility of L-4F in the treatment of inflammation that is mediated by endotoxin-activated neutrophils.

TLR4/NF-κB signaling contributes to chronic unpredictable mild stress-induced atherosclerosis in ApoE-/- mice

Objective

Chronic stress is an important risk factor for atherosclerotic diseases. Our previous studies have shown that chronic unpredictable mild stress (CUMS) accelerates atherosclerosis and up-regulates TLR4/NF-κB expression in apoE^-/- mice. However, TLR4/NF-κB signaling whether directly contributes to the development of atherosclerosis in CUMS mice is unclear. We hypothesized that the interference of TLR4/NF-κB can ameliorate CUMS-induced inflammation and atherosclerosis in apoE^-/- mice.

Methods

ApoE^-/- mice were exposed to 12 weeks CUMS. Ad-siRNA TLR4 was given by tail vein injection (10 μl/mouse, every 5 days), and PDTC (an inhibitor of NF-κB) was given by intraperitoneal injection (60 mg/kg, once a day). Plasma corticosterone concentrations were determined by solid-phase ¹²⁵I radioimmunoassay. Atherosclerosis lesions in aortic sinuses were evaluated and quantified by IMAGEPRO PLUS. Western blotting was used to detect the expression of TLR4, NF-κB, and IL-1β in aortas of the mice. Plasma lipid profiles, IL-1β, TNF-α, and MCP-1 were measured by ELISA.

Results

Our results indicated that CUMS apoE^-/- mice treatment with siRNA TLR4 significantly decreased atherosclerosis and down-regulated TLR4, NF-κB, and inflammatory cytokines. PDTC also remarkably reduced atherosclerosis and the levels of IL-1β, TNF-α and MCP-1 in plasma. However, Treatment with siRNA TLR4 or PDTC had no effect on plasma corticosterone levels, and lipid profiles.

Conclusions

TLR4/NF-κB pathway may participate in CUMS-induced atherosclerosis through activation of proinflammatory cytokines in apoE^-/- mice. Our data may provide a new potential therapeutic target for prevention of CUMS -induced atherosclerosis.

EPA and DHA exposure alters the inflammatory response but not the surface expression of Toll-like receptor 4 in macrophages

Dietary intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and their respective enrichment in cell membranes have been negatively associated with atherosclerotic lesion development. This effect may be mediated, in part, by dampened inflammatory response of macrophages triggered by toll-like receptor 4 (TLR4) activation. This study investigated the influence of membrane fatty acid profile on TLR4-mediated inflammation in RAW 264.7 macrophages. Cells pretreated with myristic acid (MA), EPA, DHA or vehicle control for 24 h were stimulated with ultra-pure LPS, a specific TLR4 agonist, for 6 or 24 h, corresponding to early and late stages of TNFα and IL-6 protein induction. Treatment significantly increased cell membrane MA, EPA, and DHA by 4.5-, 20.6-, and 8.9-fold, respectively. MA significantly increased IL-6 secretion 6 h post-exposure to the fatty acid, but did not change TNFα secretion in response to any other treatment condition. EPA and DHA significantly reduced TNFα secretion by 36 and 41 %, respectively, in cells stimulated for 24 h but not 6 h. In contrast, EPA and DHA significantly reduced IL-6 secretion at both 6 h (67 and 72%, respectively) and 24 h (69 and 72%, respectively). MA or DHA treatment had no significant effect compared to vehicle on factors influencing cellular LPS recognition, including LPS-cell association, and cell surface expression of TLR4, TLR4-MD2 complex, and CD14. These data suggest that membrane fatty acid profiles influence the TLR4-mediated inflammatory response in macrophages, via mechanisms that occur downstream of TLR4 receptor activation.

Targeting TLR4/MAPKs signaling pathway: A better option for therapeutic inhibition of atherosclerosis

Cardiovascular diseases, especially atherosclerosis, found to be the dreadful diseases worldwide. There are diverse pathways associated with the progression of atherosclerosis. One of the important signaling pathways to target atherosclerotic plaque rupture is toll-like receptor 4 (TLR4) Pathway. Several studies are available for illustrating the role of TLR4 in health and diseases. Different types of immune cell are activated in atherosclerosis but primary cells that are activated by the TLR4 signaling are macrophages and endothelial cells. Mechanisms by which macrophages uptake lipids are diverse and it is very important to target signaling pathway responsible for controlling foam cell formation. The process of macrophages transformed foam cell formation is the critical event in progression of atherosclerotic lesion and TLR4 found to have actively participate in the event through mitogen activated protein kinases (MAPKs) activation. The activation of MAPKs signaling pathway leads to the accumulation of cholesterol in the macrophages and also contribute to the dissociation of IκB and the nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 subunit, thereby activating key inflammatory cascade activation by MAPKs/NF-κB signaling pathway to induce toxicity by activating different inflammatory parameters. Hence, the review focussed on exploring the role of TLR4/MAPKs signaling pathway for the therapeutic inhibition of atherosclerosis.

Relationship between toll-like receptor 4 levels in aorta and severity of atherosclerosis

OBJECTIVE

To investigate the relationship between levels of toll-like receptor 4 (TLR4) protein in aortic tissue and the severity of atherosclerosis in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

Samples of ascending aorta and renal artery were collected from patients undergoing CABG surgery or kidney donation, respectively. TLR4 levels were determined by immunohistochemistry. Coronary angiography was performed to determine atherosclerosis severity via Gensini score.

RESULTS

TLR4 was present at high levels in aortic tissues from patients (n = 46), and was absent from renal artery tissue (controls; n = 11). There was a significant positive correlation between Gensini score and TLR4 level in the patient group.

CONCLUSIONS

TLR4 may play an important role in atherosclerosis and could be a potential therapeutic target for treatment of coronary artery disease. Discarded aortic tissue obtained during CABG surgery provides a new approach to the study of the pathogenesis of atherosclerosis.

Atherogenesis and iron: from epidemiology to cellular level

Iron accumulates in human atherosclerotic lesions but whether it is a cause or simply a downstream consequence of the atheroma formation has been an open question for decades. According to the so called "iron hypothesis," iron is believed to be detrimental for the cardiovascular system, thus promoting atherosclerosis development and progression. Iron, in its catalytically active form, can participate in the generation of reactive oxygen species and induce lipid-peroxidation, triggering endothelial activation, smooth muscle cell proliferation and macrophage activation; all of these processes are considered to be proatherogenic. On the other hand, the observation that hemochromatotic patients, affected by life-long iron overload, do not show any increased incidence of atherosclerosis is perceived as the most convincing evidence against the "iron hypothesis." Epidemiological studies and data from animal models provided conflicting evidences about the role of iron in atherogenesis. Therefore, more careful studies are needed in which issues like the source and the compartmentalization of iron will be addressed. This review article summarizes what we have learnt about iron and atherosclerosis from epidemiological studies, animal models and cellular systems and highlights the rather contributory than innocent role of iron in atherogenesis.

Toll-like receptor 4 mediates inflammatory cytokine secretion in smooth muscle cells induced by oxidized low-density lipoprotein

Oxidized low-density lipoprotein (oxLDL)-regulated secretion of inflammatory cytokines in smooth muscle cells (SMCs) is regarded as an important step in the progression of atherosclerosis; however, its underlying mechanism remains unclear. This study investigated the role of toll-like receptor 4 (TLR4) in oxLDL-induced expression of inflammatory cytokines in SMCs both in vivo and in vitro. We found that the levels of TLR4, interleukin 1-β (IL1-β), tumor necrosis factor-α (TNFα), monocyte chemoattractant protein 1 (MCP-1) and matrix metalloproteinase-2 (MMP-2) expression were increased in the SMCs of atherosclerotic plaques in patients with femoral artery stenosis. In cultured primary arterial SMCs from wild type mice, oxLDL caused dose- and time-dependent increase in the expression levels of TLR4 and cytokines. These effects were significantly weakened in arterial SMCs derived from TLR4 knockout mice (TLR4-/-). Moreover, the secretion of inflammatory cytokines was blocked by TLR4-specific antibodies in primary SMCs. Ox-LDL induced activation of p38 and NFκB was also inhibited in TLR4-/- primary SMCs or when treated with TLR4-specific antibodies. These results demonstrated that TLR4 is a crucial mediator in oxLDL-induced inflammatory cytokine expression and secretion, and p38 and NFκB activation.

Wnt5a, TLR2 and TLR4 are elevated in advanced human atherosclerotic lesions

Objective and design

Atherosclerosis (ATH) is a chronic inflammatory disease that involves cascades of signaling events mediated by various effector proteins. Here we sought to determine if the expression of Wnt5a, a secreted glycoprotein, is altered in discrete regions of the arterial plaque.

Methods

Atherosclerotic plaque tissues from 14 human subjects undergoing elective carotid endarterectomy were used in this study. Immunohistochemistry and laser capture microdissection combined with quantitative real-time PCR were used to determine the expression of Wnt5a and Toll-like receptors (TLRs) in different sections of the arterial lesions. Atherosclerotic serum samples (n = 30) and serum from healthy subjects (n = 16) were quantified for Wnt5a using an enzyme-linked immunosorbent assay (ELISA).

Results

The data analysis revealed that Wnt5a transcripts and protein were elevated in advanced arterial lesions relative to less advanced arterial lesions; that Wnt5a expression correlated with the presence of TLR4 and TLR2 transcripts; and that the average amount of Wnt5a protein present in atherosclerotic patient serum was significantly higher compared to healthy controls.

Conclusions

This study is the first to provide evidence that the expression of Wnt5a increases as the disease progresses to a more advanced stage, and that this expression is coincident with that of TLR2 and TLR4. In addition, we found that the average Wnt5a levels in the serum of atherosclerotic patients are elevated relative to healthy controls, which is consistent with the hypothesis that Wnt5a plays a role in ATH.

Comparison of anti-endotoxin activity of apoE and apoA mimetic derivatives of a model amphipathic peptide 18A

Endotoxemia is a major cause of chronic inflammation, and is an important pathogenic factor in the development of metabolic syndrome and atherosclerosis. Human apolipoprotein E (apoE) and apoA-I are protein components of high-density lipoprotein, which have strong anti-endotoxin activity. Here, we compared anti-endotoxin activity of Ac-hE18A-NH2 and 4F peptides, modified from model amphipathic helical 18A peptide, to mimic, respectively, apoE and apoA-I properties. Ac-hE18A-NH2, stronger than 4F, inhibited endotoxin activity and disaggregated Escherichia coli 055:B5 (wild smooth serotype). Ac-hE18A-NH2 and 4F inhibited endotoxin activity of E. coli 026:B6 (rough-like serotype) to a similar degree. This suggests that Ac-hE18A-NH2 as a dual-domain molecule might interact with both the lipid A and headgroup of smooth LPS, whereas 4F binds lipid A. In C57BL/6 mice, Ac-hE18A-NH2 was superior to 4F in inhibiting the inflammatory responses mediated by E. coli 055:B5, but not E. coli 026:B6. However, in THP-1 cells, isolated human primary leukocytes, and whole human blood, Ac-hE18A-NH2 reduced responses more strongly than 4F to both E. coli serotypes either when peptides were pre-incubated or co-incubated with LPS, indicating that Ac-hE18A-NH2 also has strong anti-inflammatory effects independent of endotoxin-neutralizing properties. In conclusion, Ac-hE18A-NH2 is more effective than 4F in inhibiting LPS-mediated inflammation, which opens prospective clinical applications for Ac-hE18A-NH2.

Toll-like receptor 4 gene polymorphisms and acute coronary syndrome: no association in a Mexican population

OBJECTIVE

The objective of this study was to establish the role of the TLR-4 gene polymorphisms in individuals in risk of developing ACS.

METHODS

The study included 457 Mexican patients with ACS and 283 control individuals. The TLR-4 Asp299Gly and TLR-4 Thr399Ile single nucleotide polymorphisms were genotyped using 5' exonuclease TaqMan genotyping assays on an 7900HT Fast real-time PCR system according to manufacturer's instructions (Applied Biosystems, Foster City, USA).

RESULTS

The results obtained in this study showed that the frequency of the two polymorphisms (TLR-4 Asp299Gly and TLR-4 Thr399Ile) studied were similar between patients with ACS and healthy controls. Multiple logistic regression analysis showed that the largest risk factor for ACS development was given by smoking (11.88-fold increased risk), hypertension (4.32-fold increased risk), type II diabetes (3.44-fold increased risk), gender (2.32-fold increased risk), and dyslipidemia (1.52-fold increased risk).

CONCLUSION

The Asp299Gly and Thr399Ile polymorphisms were not associated with susceptibility to ACS in the Mexican population.

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.

Toll-like receptor 4 gene Asp299Gly polymorphism in ischemic cerebrovascular disease: a meta-analysis

Epidemiological studies have evaluated the association between Toll-like receptor 4 (TLR4) gene Asp299Gly (rs4986790) polymorphism and the risk of ischemic cerebrovascular disease, but the results are inconsistent. In an effort to clarify earlier inconclusive results, a meta-analysis was performed. We searched the PubMed, Web of Science, Embase, Cochrane database, Clinicaltrials.gov, Current Controlled Trials, CNKI, CBMdisc, Chinese Clinical Trial Registry and Google Scholar until up to 20 July 2013. Additionally, hand searching of the references of identified articles was performed. Original observational studies investigating the association between TLR4 gene Asp299Gly polymorphism and ischemic cerebrovascular disease risk were included. All statistical analyses were performed using Stata 11.0. The search strategy identified 1038 potentially relevant articles, seven of which were included in the final meta-analysis, covering a total of 1767 cases and 2785 controls. Overall, no significant association was found between TLR4 gene Asp299Gly polymorphism and ischemic cerebrovascular disease risk (for G allele versus A allele: OR = 0.95, 95% CI = 0.75-1.21, p = 0.69; for G/G+A/G versus A/A: OR = 0.96, 95% CI = 0.75-1.22, p = 0.73). In addition, the similar results were obtained in the sensitivity analysis based on studies with the high quality. In summary, the present meta-analysis indicates that TLR4 gene Asp299Gly polymorphism is not associated with increased ischemic cerebrovascular disease risk.

Race and gender variation in response to evoked inflammation

BACKGROUND

Race- and gender-variation in innate immunity may contribute to demographic differences in inflammatory and cardiometabolic disease; yet their influence on dynamic responses during inflammatory stress is poorly understood. Our objective was to examine race and gender influence on the response to experimental endotoxemia.

METHODS

The Genetics of Evoked Responses to Niacin and Endotoxemia (GENE) study was designed to investigate regulation of inflammatory and metabolic responses during low-grade endotoxemia (LPS 1 ng/kg intravenously) in healthy individuals (median age 24, IQR=7) of European (EA; n=193, 47% female) and African ancestry (AA; n=101, 59% female).

RESULTS

Baseline clinical, metabolic, and inflammatory biomarkers by race and gender were consistent with epidemiological literature; pre-LPS cytokines (e.g. median (IQR) IL-6, 2.7 (2) vs.2.1 (2) pg/ml, P=0.001) were higher in AA than EA. In contrast, acute cytokine responses during endotoxemia were lower in AA than EA (e.g. median (IQR) peak IL-1RA, 30 (38) vs.43 (45) ng/ml P=0.002) as was the induction of hepatic acute-phase proteins (e.g. median (IQR) peak CRP 12.9 (9) vs.17.4 (12) mg/L P=0.005). Further, baseline levels of cytokines were only weakly correlated with peak inflammatory responses (all r(s) <0.2) both in AA and in EA. There were less pronounced and less consistent differences in the response by gender, with males having a higher AUC for CRP response compared to females (median (IQR) AUC: 185 (112) vs. 155 (118), P=0.02).

CONCLUSIONS

We observed lower levels of evoked inflammation in response to endotoxin in AA compared with EA, despite similar or higher baseline levels of inflammatory markers in AA. Our data also suggest that levels of inflammatory biomarkers measured in epidemiological settings might not predict the degree of acute stress-response or risk of diseases characterized by activation of innate immunity.

TRIAL REGISTRATION

FDA clinicaltrials.gov registration number NCT00953667.

Influence of pentraxin 3 (PTX3) genetic variants on myocardial infarction risk and PTX3 plasma levels

PTX3 is a long pentraxin of the innate immune system produced by different cell types (mononuclear phagocytes, dendritic cells, fibroblasts and endothelial cells) at the inflammatory site. It appears to have a cardiovascular protective function by acting on the immune-inflammatory balance in the cardiovascular system. PTX3 plasma concentration is an independent predictor of mortality in patients with acute myocardial infarction (AMI) but the influence of PTX3 genetic variants on PTX3 plasma concentration has been investigated very little and there is no information on the association between PTX3 variations and AMI. Subjects of European origin (3245, 1751 AMI survivors and 1494 controls) were genotyped for three common PTX3 polymorphisms (SNPs) (rs2305619, rs3816527, rs1840680). Genotype and allele frequencies of the three SNPs and the haplotype frequencies were compared for the two groups. None of the genotypes, alleles or haplotypes were significantly associated with the risk of AMI. However, analysis adjusted for age and sex indicated that the three PTX3 SNPs and the corresponding haplotypes were significantly associated with different PTX3 plasma levels. There was also a significant association between PTX3 plasma concentrations and the risk of all-cause mortality at three years in AMI patients (OR 1.10, 95% CI: 1.01–1.20, p = 0.02). Our study showed that PTX3 plasma levels are influenced by three PTX3 polymorphisms. Genetically determined high PTX3 levels do not influence the risk of AMI, suggesting that the PTX3 concentration itself is unlikely to be even a modest causal factor for AMI. Analysis also confirmed that PTX3 is a prognostic marker after AMI.