Hyperglycemia amplifies TLR-mediated inflammatory response of M(IL4) macrophages to dyslipidemic ligands

Hyperglycemia is critical for initiation of diabetic vascular complications. We systemically addressed the role of hyperglycemia in the regulation of TLRs in primary human macrophages. Expression of TLRs (1-9) was examined in monocyte-derived M(NC), M(IFNγ), and M(IL4) differentiated in normoglycemic and hyperglycemic conditions. Hyperglycemia increased expression of TLR1 and TLR8 in M(NC), TLR2 and TLR6 in M(IFNγ), and TLR4 and TLR5 in M(IL4). The strongest effect of hyperglycemia in M(IL4) was the upregulation of the TLR4 gene and protein expression. Hyperglycemia amplified TLR4-mediated response of M(IL4) to lipopolysaccharide by significantly enhancing IL1β and modestly suppressing IL10 production. In M(IL4), hyperglycemia in combination with synthetic triacylated lipopeptide (TLR1/TLR2 ligand) amplified expression of TLR4 and production of IL1β. In summary, hyperglycemia enhanced the inflammatory potential of homeostatic, inflammatory, and healing macrophages by increasing specific profiles of TLRs. In combination with dyslipidemic ligands, hyperglycemia can stimulate a low-grade inflammatory program in healing macrophages supporting vascular diabetic complications.

Expanding role of deoxyribonucleic acid-sensing mechanism in the development of lifestyle-related diseases

In lifestyle-related diseases, such as cardiovascular, metabolic, respiratory, and kidney diseases, chronic inflammation plays a causal role in their pathogenesis; however, underlying mechanisms of sterile chronic inflammation are not well-understood. Previous studies have confirmed the damage of cells in these organs in the presence of various risk factors such as diabetes, dyslipidemia, and cigarette smoking, releasing various endogenous ligands for pattern recognition receptors. These studies suggested that nucleic acids released from damaged tissues accumulate in these tissues, acting as an endogenous ligand. Undamaged DNA is an integral factor for the sustenance of life, whereas, DNA fragments, especially those from pathogens, are potent activators of the inflammatory response. Recent studies have indicated that inflammatory responses such as the production of type I interferon (IFN) induced by DNA-sensing mechanisms which contributes to self-defense system in innate immunity participates in the progression of inflammatory diseases by the recognition of nucleic acids derived from the host, including mitochondrial DNA (mtDNA). The body possesses several types of DNA sensors. Toll-like receptor 9 (TLR9) recognizes DNA fragments in the endosomes. In addition, the binding of DNA fragments in the cytosol activates cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS), resulting in the synthesis of the second messenger cyclic GMP-AMP (cGAMP). The binding of cGAMP to stimulator of interferon genes (STING) activates NF-κB and TBK-1 signaling and consequently the production of many inflammatory cytokines including IFNs. Numerous previous studies have demonstrated the role of DNA sensors in self-defense through the recognition of DNA fragments derived from pathogens. Beyond the canonical role of TLR9 and cGAS-STING, this review describes the role of these DNA-sensing mechanism in the inflammatory responses caused by endogenous DNA fragments, and in the pathogenesis of lifestyle-related diseases.

Innate Immune Activation and Circulating Inflammatory Markers in Preschool Children

Early childhood is characterised by repeated infectious exposures that result in inflammatory responses by the innate immune system. In addition, this inflammatory response to infection is thought to contribute to the epidemiological evidence linking childhood infection and adult non-communicable diseases. Consequently, the relationship between innate immune responses and inflammation during early life may inform prevention of NCDs later in life. In adults, non-genetic host factors such as age, sex, and obesity, strongly impact cytokine production and circulating mediators, but data in children are lacking. Here, we assessed cytokine responses and inflammatory markers in a population of healthy preschool children (mean age 4.2 years). We studied associations between cytokines, plasma inflammatory markers and non-genetic host factors, such as sex, age, adiposity, season, and immune cell composition. Similar to adults, boys had a higher inflammatory response than girls, with IL-12p70 and IL-10 upregulated following TLR stimulation. Adiposity and winter season were associated with increased circulating inflammatory markers but not cytokine production. The inflammatory markers GlycA and hsCRP were positively associated with production of a number of cytokines and may therefore reflect innate immune function and inflammatory potential. This dataset will be informative for future prospective studies relating immune parameters to preclinical childhood NCD phenotypes.

Effects of Ruanmailing in Blocking Early Stages of Atherosclerosis by TNF-α Regulation via Kir2.1

Objective

Ruanmailing oral solution consists of 16 herbs, has anti-lipid peroxidation activity, protects vascular endothelial cells, and improves vascular elasticity. It is an effective drug for the treatment of atherosclerosis (AS). The objective of this study was to investigate the mechanism underlying the antiatherosclerotic effects of Ruanmailing oral solution.

Methods

Macrophages were isolated, cultured, and divided into the macrophage control; macrophage foam cell; and low-, medium-, and high-concentration Ruanmailing groups. Cell proliferation was analyzed by cell counting kit-8 (CCK-8) assay, and the expression levels of inward-rectifier potassium ion channel 2.1 (Kir2.1) and tumor necrosis factor (TNF)-α were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses.

Results

CCK-8 assay results showed that the tested concentrations of Ruanmailing solution did not affect macrophage proliferation. RT-PCR and Western blot assays indicated that TNF-α expression increased significantly with the formation of macrophage foam cells (P < 0.05). In addition, significant decreases in Kir2.1 and TNF-α expression were observed following treatment with various concentrations of Ruanmailing (P < 0.05).

Conclusion

Based on the results, Ruanmailing affects macrophage foam cell formation by regulating Kir2.1 expression, which in turn reduces TNF-α expression and exerts antiatherosclerotic effects. These findings provide a scientific basis for the use of traditional Chinese medicine for AS treatment.

Emerging evidence of Toll-like receptors as a putative pathway linking maternal inflammation and neurodevelopmental disorders in human offspring: A systematic review

Inflammation is increasingly recognised to play a major role in gene-environment interactions in neurodevelopmental disorders (NDDs). The effects of aberrant immune responses to environmental stimuli in the mother and in the child can affect neuroimmune signalling that is central to brain development. Toll-like receptors (TLR) are the best known innate immune pattern and danger recognition sensors to various environmental threats. In animal models, maternal immune activation (MIA), secondary to inflammatory factors including maternal gestational infection, obesity, diabetes, and stress activate the TLR pathway in maternal blood, placenta, and fetal brain, which correlate with offspring neurobehavioral abnormalities. Given the central role of TLR activation in animal MIA models, we systematically reviewed the human evidence for TLR activation and response to stimulation across the maternal-fetal interface. Firstly, we included 59 TLR studies performed in peripheral blood of adults in general population (outside of pregnancy) with six chronic inflammatory factors which have epidemiological evidence for increased risk of offspring NDDs, namely, obesity, diabetes mellitus, depression, low socio-economic status, autoimmune diseases, and asthma. Secondly, eight TLR studies done in human pregnancies with chronic inflammatory factors, involving maternal blood, placenta, and cord blood, were reviewed. Lastly, ten TLR studies performed in peripheral blood of individuals with NDDs were included. Despite these studies, there were no studies which examined TLR function in both the pregnant mother and their offspring. Increased TLR2 and TLR4 mRNA and/or protein levels in peripheral blood were common in obesity, diabetes mellitus, depression, autoimmune thyroid disease, and rheumatoid arthritis. To a lesser degree, TLR 3, 7, 8, and 9 activation were found in peripheral blood of humans with autoimmune diseases and depression. In pregnancy, increased TLR4 mRNA levels were found in the peripheral blood of women with diabetes mellitus and systemic lupus erythematosus. Placental TLR activation was found in mothers with obesity or diabetes. Postnatally, dysregulated TLR response to stimulation was found in peripheral blood of individuals with NDDs. This systematic review found emerging evidence that TLR activation may represent a mechanistic link between maternal inflammation and offspring NDD, however the literature is incomplete and longitudinal outcome studies are lacking. Identification of pathogenic mechanisms in MIA could create preventive and therapeutic opportunities to mitigate NDD prevalence and severity.

Extremes of age are associated with differences in the expression of selected pattern recognition receptor genes and ACE2, the receptor for SARS-CoV-2: implications for the epidemiology of COVID-19 disease

Background

Older aged adults and those with pre-existing conditions are at highest risk for severe COVID-19 associated outcomes.

Methods

Using a large dataset of genome-wide RNA-seq profiles derived from human dermal fibroblasts (GSE113957) we investigated whether age affects the expression of pattern recognition receptor (PRR) genes and ACE2, the receptor for SARS-CoV-2.

Results

Extremes of age are associated with increased expression of selected PRR genes, ACE2 and four genes that encode proteins that have been shown to interact with SAR2-CoV-2 proteins.

Conclusions

Assessment of PRR expression might provide a strategy for stratifying the risk of severe COVID-19 disease at both the individual and population levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-00970-7.

Emerging roles of Toll-like receptor 9 in cardiometabolic disorders

Growing evidence suggests that damage-associated molecule patterns (DAMPs) and their receptors, pattern recognition receptors (PRRs), are associated with the progression of cardiometabolic disorders, including obesity-related insulin resistance and atherosclerosis. Cardiometabolic disorders share sterile chronic inflammation as a major cause; however, the exact mechanisms are still obscure. Toll-like receptor 9 (TLR9), one of the nucleic acid-sensing TLRs, recognizes DNA fragments derived from pathogens and contributes to self-defense by activation of the innate immune system. In addition, previous studies demonstrated that TLR9 recognizes DNA fragments released from host cells, accelerating sterile inflammation, which is associated with inflammatory diseases such as autoimmune diseases. In obese adipose tissue and atherosclerotic vascular tissue, various stresses release DNA fragments and/or nuclear proteins as DAMPs from degenerated adipocytes and vascular cells. Recent studies indicated that the activation of TLR9 in immune cells including macrophages and dendritic cells by recognition of these DAMPs promotes inflammation in these tissues, which causes cardiometabolic disorders. This review discusses recent advances in understanding the role of sterile inflammation associated with TLR9 and its endogenous ligands in cardiometabolic disorders. New insights into innate immunity may provide better understanding of cardiometabolic disorders and new therapeutic options for these major health threats in recent decades.

The Role of Toll-like Receptors in Atherothrombotic Cardiovascular Disease

Toll-like receptors (TLRs) are dominant components of the innate immune system. Activated by both pathogen-associated molecular patterns and damage-associated molecular patterns, TLRs underpin the pathology of numerous inflammation related diseases that include not only immune diseases, but also cardiovascular disease (CVD), diabetes, obesity, and cancers. Growing evidence has demonstrated that TLRs are involved in multiple cardiovascular pathophysiologies, such as atherosclerosis and hypertension. Specifically, a trial called the Canakinumab Anti-inflammatory Thrombosis Outcomes Study showed the use of an antibody that neutralizes interleukin-1β, reduces the recurrence of cardiovascular events, demonstrating inflammation as a therapeutic target and also the research value of targeting the TLR system in CVD. In this review, we provide an update of the interplay between TLR signaling, inflammatory mediators, and atherothrombosis, with an aim to identify new therapeutic targets for atherothrombotic CVD.

TLR2 and TLR4 Surface and Gene Expression in White Blood Cells after Fasting and Oral Glucose, Lipid and Protein Challenges: Influence of Obesity and Sex Hormones

We studied if macronutrients of the diet have different effects on leukocyte activation, and if these effects are influenced by sex hormones or obesity. We analyzed leukocyte cell surface and gene expression of toll-like receptors 2 and 4 (TLR2 and TLR4) during fasting and after macronutrient loads in women with polycystic ovary syndrome and female and male controls. Fasting TLR2 surface expression in neutrophils was higher in men than in women. Obese subjects presented higher TLR2 gene expression than nonobese individuals, particularly in men. In contrast, surface TLR4 expression was lower in men and in obese individuals. Postprandial cell-surface expression decreased similarly after all macronutrient loads. Neutrophil TLR2 decreased only in obese subjects whereas TLR4 showed a greater decrease in nonobese individuals. However, TLR2 gene expression increased after glucose ingestion and decreased during the lipid load, while TLR4 was induced in response to lipids and mostly to glucose. Postprandial TLR gene expression was not influenced by group of subjects or obesity. Both cell-surface and gene postprandial expression inversely correlated with their fasting levels. These responses suggest a transient compensatory response aiming to prevent postprandial inflammation. However, obesity and sex hormones showed opposite influences on surface expression of TLR2 and TLR4, but not on their gene expression, pointing to regulatory posttranscriptional mechanisms.

Pattern Recognition Receptor-Mediated Chronic Inflammation in the Development and Progression of Obesity-Related Metabolic Diseases

Obesity-induced chronic inflammation is known to promote the development of many metabolic diseases, especially insulin resistance, type 2 diabetes mellitus, nonalcoholic fatty liver disease, and atherosclerosis. Pattern recognition receptor-mediated inflammation is an important determinant for the initiation and progression of these metabolic diseases. Here, we review the major features of the current understanding with respect to obesity-related chronic inflammation in metabolic tissues, focus on Toll-like receptors and nucleotide-binding oligomerization domain-like receptors with an emphasis on how these receptors determine metabolic disease progression, and provide a summary on the development and progress of PRR antagonists for therapeutic intervention.

TLR4 triggered complex inflammation in human pancreatic islets

Type 2 Diabetes (T2D) is strongly associated with obesity and inflammation. Toll-like receptor-4 (TLR-4) is the major pro-inflammatory pathway with its ligands and downstream products increased systemically in T2D and in at-risk individuals. Detailed mechanisms of the complex proinflammatory response in pancreatic islets remain unknown. In isolated human islets LPS induced IL-1β, IL-6, IL-8 and TNF production in a TLR4-dependent manner and severely impaired β-cell survival and function. IL-6 antagonism improved β-cell function. IL-8, which was identified specifically in α-cells, initiated monocyte migration, a process fully blocked by IL-8 neutralization. The TLR4 response was potentiated in obese donors; with higher IL-1β, IL-6 and IL-8 expression than in non-obese donors. TLR4 activation leads to a complex multi-cellular inflammatory response in human islets, which involves β-cell failure, cytokine production and macrophage recruitment to islets. In obesity, the amplified TLR4 response may potentiate β-cell damage and accelerate diabetes progression.

Udenafil, a Phosphodiesterase 5 Inhibitor, Reduces Body Weight in High-Fat-Fed Mice

Purpose

High-fat (HF) feeding induces hypothalamic leptin resistance via the activation of toll-like receptor 4 (TLR4). TLR4 deficiency confers resistance to diet-induced obesity. Udenafil, an anti-impotence drug, inhibits TLR4 in airway epithelial cells in vitro. In this study, we evaluated whether udenafil suppressed the hypothalamic expression of TLR4 and reduced body weight.

Materials and Methods

The hypothalamic expression of TLR4, phosphodiesterase 5 (PDE5), nuclear factor-κB (NF-κB), and myeloid differentiation primary response gene 88 (Myd88) was analyzed by real-time polymerase chain reaction after treating mice for 2 days with udenafil (0, 12, 120, or 600 µg/d). Furthermore, the hypothalamic expression of TLR4, pro-opiomelanocortin (POMC), and neuropeptide Y (NPY) was analyzed after 9 days' treatment with udenafil and/or leptin. We also measured body weight and food intake following 9 days of udenafil and/or leptin treatment in control- and HF-fed mice.

Results

Udenafil suppressed hypothalamic TLR4 mRNA expression dose-dependently. The changes were associated with decreased PDE5, NF-κB, and Myd88 expression. Udenafil treatment for 9 days reduced body weight and caloric intake in HF-fed mice. This may have been associated with the suppression of NPY expression that was elevated by HF feeding. POMC expression was not affected by udenafil. However, udenafil did not augment the effects of leptin on the reduction of body weight and caloric intake in HF-fed mice.

Conclusions

These results suggested that udenafil reduced body weight by suppressing hypothalamic TLR4 mRNA expression in HF-fed mice and the combination effect of udenafil and leptin was additive rather than synergistic.

The disintegrin, trimucrin, suppresses LPS-induced activation of phagocytes primarily through blockade of NF-κB and MAPK activation

In addition to antiplatelet activity, disintegrin, a small-mass RGD-containing polypeptide, has been shown to exert anti-inflammatory effects but the mechanism involved remains unclear. In this study, we report that trimucrin, a disintegrin from the venom of Trimeresurus mucrosquamatus, inhibits lipopolysaccharide (LPS)-induced stimulation of THP-1 and RAW 264.7 cells. We also investigate the underlying mechanism. Trimucrin decreased the release of proinflammatory cytokines including tumor necrosis factor α (TNFα), interleukin-6 (IL-6), nitric oxide, and reactive oxygen species (ROS), and inhibited the adhesion and migration of LPS-activated phagocytes. Trimucrin significantly blocked the expression of nuclear factor kappaB (NF-κB)-related downstream inducible enzymes such as inducible nitric oxide synthase (iNOS) and COX-2. In addition, its anti-inflammatory effect was associated with the decreased mitogen-activated protein kinase (MAPK) phosphorylation. Furthermore, trimucrin concentration dependently inhibited LPS-induced phosphorylation of focal adhesion kinase (FAK), PI3K, and Akt. Trimucrin also reversed the DNA-binding activity of NF-κB by suppressing the LPS-induced nuclear translocation of p65 and the cytosolic IκB release. Flow cytometric analyses showed that trimucrin bound to cells in a concentration-dependent manner. The anti-αVβ3 mAb also specifically decreased the binding of fluorescein isothiocyanate (FITC)-conjugated trimucrin. Binding assays demonstrated that integrin αVβ3 was the binding site for trimucrin on THP-1 and RAW 264.7 cells. In conclusion, we showed that trimucrin decreases the inflammatory reaction through the attenuation of iNOS expression and nitric oxide (NO) production by blocking MAP kinase and the NF-κB activation in LPS-stimulated THP-1 and RAW 264.7 cells.

Invasive surgery reduces infarct size and preserves cardiac function in a porcine model of myocardial infarction

Reperfusion injury following myocardial infarction (MI) increases infarct size (IS) and deteriorates cardiac function. Cardioprotective strategies in large animal MI models often failed in clinical trials, suggesting translational failure. Experimentally, MI is induced artificially and the effect of the experimental procedures may influence outcome and thus clinical applicability. The aim of this study was to investigate if invasive surgery, as in the common open chest MI model affects IS and cardiac function. Twenty female landrace pigs were subjected to MI by transluminal balloon occlusion. In 10 of 20 pigs, balloon occlusion was preceded by invasive surgery (medial sternotomy). After 72 hrs, pigs were subjected to echocardiography and Evans blue/triphenyl tetrazoliumchloride double staining to determine IS and area at risk. Quantification of IS showed a significant IS reduction in the open chest group compared to the closed chest group (IS versus area at risk: 50.9 ± 5.4% versus 69.9 ± 3.4%, P = 0.007). End systolic LV volume and LV ejection fraction measured by echocardiography at follow-up differed significantly between both groups (51 ± 5 ml versus 65 ± 3 ml, P = 0.033; 47.5 ± 2.6% versus 38.8 ± 1.2%, P = 0.005). The inflammatory response in the damaged myocardium did not differ between groups. This study indicates that invasive surgery reduces IS and preserves cardiac function in a porcine MI model. Future studies need to elucidate the effect of infarct induction technique on the efficacy of pharmacological therapies in large animal cardioprotection studies.

A therapeutic role for vitamin D on obesity-associated inflammation and weight-loss intervention

Vitamin D plays an essential role in the regulation of skeletal metabolism as well as calcium and phosphate homeostasis, while vitamin D receptor (VDR) regulates de novo lipid synthesis, thereby contributing to the development of obesity. Furthermore, obese individuals are at a greater risk for vitamin D deficiency which may increase the potential risk for chronic inflammation, insulin resistance, and metabolic syndrome. While acute exercise enhances the activation of inflammatory signaling pathways, chronic exercise training may attenuate elevated pro-inflammatory cytokine production, resulting in the improvement of cardiovascular and metabolic health in obese individuals. Supplementation with vitamin D coupled with exercise or mild caloric restriction has been shown to improve markers of fitness and inflammation as well as cholesterol. Therefore, this review primarily addresses the impact of vitamin D deficiency in obesity-related inflammatory imbalances and how exercise and weight-loss interventions may enhance the beneficial effects on vitamin D-mediated inflammation in obesity.

TLR4 at the Crossroads of Nutrients, Gut Microbiota, and Metabolic Inflammation

Obesity is accompanied by the activation of low-grade inflammatory activity in metabolically relevant tissues. Studies have shown that obesity-associated insulin resistance results from the inflammatory targeting and inhibition of key proteins of the insulin-signaling pathway. At least three apparently distinct mechanisms-endoplasmic reticulum stress, toll-like receptor (TLR) 4 activation, and changes in gut microbiota-have been identified as triggers of obesity-associated metabolic inflammation; thus, they are expected to represent potential targets for the treatment of obesity and its comorbidities. Here, we review the data that place TLR4 in the center of the events that connect the consumption of dietary fats with metabolic inflammation and insulin resistance. Changes in the gut microbiota can lead to reduced integrity of the intestinal barrier, leading to increased leakage of lipopolysaccharides and fatty acids, which can act upon TLR4 to activate systemic inflammation. Fatty acids can also trigger endoplasmic reticulum stress, which can be further stimulated by cross talk with active TLR4. Thus, the current data support a connection among the three main triggers of metabolic inflammation, and TLR4 emerges as a link among all of these mechanisms.

oxLDL/β2GPI/anti-β2GPI complex induced macrophage differentiation to foam cell involving TLR4/NF-kappa B signal transduction pathway

Macrophage-derived foam cell formation is a hallmark of atherosclerosis. It has been reported that oxidized low density lipoprotein (oxLDL) inducing formation of foam cells and expression of inflammatory molecules are partly mediated by toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) pathway. However, whether oxLDL/β2-glycoprotein I/anti-β2-glycoprotein I (oxLDL/β2GPI/anti-β2GPI) complex enhanced formation of foam cells involving TLR4/NF-κB pathway or not has never been explored. In the current study, we focused on investigating the transformation of peritoneal macrophages from BALB/c mice into foam cells induced by the three complexes, and the involvement of TLR4 as well as its downstream signal molecule NF-κB. The results showed that treatment of macrophages with oxLDL/β2GPI/anti-β2GPI complex could markedly increase intracellular lipid loading and expression of TLR4, phosphorylated NF-κB p65 (p-NF-κB p65), monocyte chemoattractant protein-1 (MCP-1), as well as tissue factor (TF). The oxLDL and oxLDL/β2GPI/anti-β2GPI complex induced formation of foam cells and expression of p-NF-κB p65 were significantly reduced, while macrophages were pre-treated with TLR4 inhibitor TAK-242. Meanwhile, both TAK-242 and NF-κB inhibitor PDTC could remarkably inhibit oxLDL, oxLDL/β2GPI/anti-β2GPI complex, as well as LPS increased MCP-1 and TF levels. Nevertheless, β2GPI/anti-β2GPI complex-induced MCP-1 and TF mRNA expression were inhibited by TAK-242 rather than PDTC, although TF activity was significantly reduced by both of the inhibitors. In conclusion, our results indicate that oxLDL/β2GPI/anti-β2GPI complex could enhance the conversion of macrophages into foam cells and the process may be at least partly mediated by TLR4/NF-κB pathway, which may contribute to the accelerated development of atherosclerosis in APS.

Flow cytometry and gene expression profiling of immune cells of the carotid plaque and peripheral blood

OBJECTIVES

The relative contribution of the local vs. peripheral inflammation to the atherothrombotic processes is unknown. We compared the inflammatory status of the immune cells of the carotid plaque with similar cells in peripheral circulation of patients with advanced carotid disease (PCDs).

METHODS

Mononuclear cells (MNCs) were extracted from carotid endarterectomy (CEA) samples by enzymatic digestion and subsequent magnetic cell sorting. The cell surface antigenic expressions, and mRNA expression levels were compared between CEA MNCs and peripheral MNCs, using flow cytometry and RT-PCR techniques.

RESULTS

The percentages of resting MNCs were lower, and activated MNCs, particularly monocytes, were higher in the CEAMNCs, as compared to the peripheral MNCs. The percentages of activated T cells and B cells were higher in the peripheral MNCs of PCDs, than in healthy controls (HCs), but the percentages of activated monocytes did not differ between the two groups. The expression levels of both pro-inflammatory/pro-thrombotic (P(38), JNKB-1, Egr-1 PAI-1, MCP-1, TF, MMP-9, HMGB-1, TNF-α, mTOR) and anti-inflammatory (PPAR-γ, TGF-β) mediators were significantly higher in the CEA MNCs as compared to the peripheral MNCs. Furthermore, MMP-9 and PPAR-γ expression levels were higher in the peripheral MNCs of PCDs than HCs.

CONCLUSION

The inflammatory status is higher in the immune cells of the carotid plaque, as compared to those cells in the peripheral blood. The altered expression levels of both pro-inflammatory/pro-thrombotic and anti-inflammatory mediators in the milieu of the plaque suggest that the balance between these various mediators may play a key role in carotid disease progression.

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

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

Pathophysiology of atherosclerosis plaque progression

Atherosclerotic plaque rupture with luminal thrombosis is the most common mechanism responsible for the majority of acute coronary syndromes and sudden coronary death. The precursor lesion of plaque rupture is thought to be a thin cap fibroatheroma (TCFA) or "vulnerable plaque". TCFA is characterised by a necrotic core with an overlying thin fibrous cap (≤65 μm) that is infiltrated by macrophages and T-lymphocytes. Intraplaque haemorrhage is a major contributor to the enlargement of the necrotic core. Haemorrhage is thought to occur from leaky vasa vasorum that invades the intima from the adventitia as the intima enlarges. The early atherosclerotic plaque progression from pathologic intimal thickening (PIT) to a fibroatheroma is thought to be the result of macrophage infiltration. PIT is characterised by the presence of lipid pools which consist of proteoglycan with lipid insudation. The conversion of the lipid pool to a necrotic core is poorly understood but is thought to occur as a result of macrophage infiltration which releases matrix metalloproteinase (MMPs) along with macrophage apoptosis that leads to the formation of a acellular necrotic core. The fibroatheroma has a thick fibrous cap that begins to thin over time through macrophage MMP release and apoptotic death of smooth muscle cells converting the fibroatheroma into a TCFA. Other causes of thrombosis include plaque erosion which is less frequent than plaque rupture but is a common cause of thrombosis in young individuals especially women <50 years of age. The underlying lesion morphology in plaque erosion consists of PIT or a thick cap fibroatheroma. Calcified nodule is the least frequent cause of thrombosis, which occurs in older individuals with heavily calcified and tortious arteries.

Innate immune function by Toll-like receptors: distinct responses in newborns and the elderly

Given the "inborn" nature of the innate immune system, it is surprising to find that innate immune function does in fact change with age. Similar patterns of distinct Toll-like-receptor-mediated immune responses come to light when one contrasts innate immune development at the beginning of life with that toward the end of life. Importantly, these developmental patterns of innate cytokine responses correlate with clinical patterns of susceptibility to disease: A heightened risk of suffering from excessive inflammation is often detected in prematurely born infants, disappears over the first few months of life, and reappears toward the end of life. In addition, risk periods for particular infections in early life reemerge in older adults. The near-mirror-image patterns that emerge in contrasts of early versus late innate immune ontogeny emphasize changes in host-environment interactions as the underlying molecular and teleologic drivers.

Oxidized LDLs inhibit TLR-induced IL-10 production by monocytes: a new aspect of pathogen-accelerated atherosclerosis

It is widely accepted that oxidized low-density lipoproteins and local infections or endotoxins in circulation contribute to chronic inflammatory process at all stages of atherosclerosis. The hallmark cells of atherosclerotic lesions-monocytes and macrophages-are able to detect and integrate complex signals derived from lipoproteins and pathogens, and respond with a spectrum of immunoregulatory cytokines. In this study, we show strong inhibitory effect of oxLDLs on anti-inflammatory interleukin-10 production by monocytes responding to TLR2 and TLR4 ligands. In contrast, pro-inflammatory tumor necrosis factor secretion was even slightly increased, when stimulated with lipopolysaccharide from Porphyromonas gingivalis-an oral pathogen associated with atherosclerosis. The oxLDLs modulatory activity may be explained by altered recognition of pathogen-associated molecular patterns, which involves serum proteins, particularly vitronectin. We also suggest an interaction between vitronectin receptor, CD11b, and TLR2. The presented data support a novel pathway for pathogen-accelerated atherosclerosis, which relies on oxidized low-density lipoprotein-mediated modulation of anti-inflammatory response to TLR ligands.

Oxidized LDLs inhibit TLR-induced IL-10 production by monocytes: a new aspect of pathogen-accelerated atherosclerosis

It is widely accepted that oxidized low-density lipoproteins and local infections or endotoxins in circulation contribute to chronic inflammatory process at all stages of atherosclerosis. The hallmark cells of atherosclerotic lesions-monocytes and macrophages-are able to detect and integrate complex signals derived from lipoproteins and pathogens, and respond with a spectrum of immunoregulatory cytokines. In this study, we show strong inhibitory effect of oxLDLs on anti-inflammatory interleukin-10 production by monocytes responding to TLR2 and TLR4 ligands. In contrast, pro-inflammatory tumor necrosis factor secretion was even slightly increased, when stimulated with lipopolysaccharide from Porphyromonas gingivalis-an oral pathogen associated with atherosclerosis. The oxLDLs modulatory activity may be explained by altered recognition of pathogen-associated molecular patterns, which involves serum proteins, particularly vitronectin. We also suggest an interaction between vitronectin receptor, CD11b, and TLR2. The presented data support a novel pathway for pathogen-accelerated atherosclerosis, which relies on oxidized low-density lipoprotein-mediated modulation of anti-inflammatory response to TLR ligands.

Enhancement of lipopolysaccharide-induced toll-like receptor 2 expression and inflammatory cytokine secretion in HUVECs under high glucose conditions

AIMS

Endothelial inflammatory responses mediated by toll-like receptors (TLRs) play an important role in atherogenesis. We aimed to investigate the exacerbation of an inflammatory response in human umbilical vein endothelial cells (HUVECs) under high glucose conditions.

MAIN METHODS

HUVECs were exposed to normal glucose (5.5 mmol/L) and high glucose (25, 50 mmol/L), alone or with lipopolysaccharide (LPS 0, 10, 100, or 1000 μg/L). Then concentrations of TNF-α and IL-6 in the culture supernatants were determined. The expression of toll-like receptor 2 (TLR2), TLR4 and NF-κB was evaluated by Western blot and RT-PCR analysis.

KEY FINDINGS

Compared with the normal glucose group, exposure of HUVECs to 50 mmol/L of glucose or 1000 μg/L of LPS significantly increased the concentrations of TNF-α and IL-6 in the culture supernatants. Neither 25 mmol/L of glucose nor low concentration of LPS (≤100 μg/L) alone had an effect on TNF-α and IL-6 release, or TLR2 expression, but they stimulated the inflammatory response and TLR2 expression under high glucose conditions (25 mmol/L) in combination. LPS (100 μg/L) did not alter the TLR4 expression in HUVECs under high glucose condition. Co-incubation with glucose and LPS increased the nuclear NF-κB expression in endothelial cells. Both NF-κB inhibitor and ROS scavenger could inhibit the enhancement of LPS-induced TLR2 expression and inflammatory cytokine secretion under high glucose conditions.

SIGNIFICANCE

We show in vitro data on the potential role of high glucose in increasing LPS-induced TLR2 expression and inflammatory cytokine secretion in HUVECs, offering a new insight into the pathophysiological pathways involved in atherosclerosis.

Anti-apolipoprotein A-1 IgG levels predict coronary artery calcification in obese but otherwise healthy individuals

We aimed at determining whether anti-apolipoprotein (apo) A-1 IgG levels are independent predictors of coronary artery calcification (CAC) and coronary endothelial dysfunction in obese and nonobese subjects without cardiovascular disease. 48 nonobese and 43 obese subjects were included. CAC score was measured by thorax scanner and defined by an Agatston score > 0. Coronary endothelial dysfunction was determined by measuring myocardial blood flow responses to cold pressor test (CPT) on PET/CT. Serum anti-apoA-1 IgG levels were measured by ELISA. Prevalence of coronary calcification was similar between the two study groups, but the prevalence of coronary endothelial dysfunction was higher in obese subjects. Anti-apoA-1 IgG levels and positivity rate were higher in obese than in nonobese individuals. CAC score was higher in anti-apoA-1 IgG positive subjects. ROC analyses indicated that anti-apoA-1 IgG levels were significant predictors of CAC > 0, but not of coronary endothelial dysfunction with a negative predictive value of 94%. Anti-apoA-1 IgG positivity was associated with a 17-fold independent increased risk of CAC > 0. In conclusion, those preliminary results indicate that anti-apoA-1 IgG autoantibodies are raised in obese subjects and independently predict the presence of coronary calcification in this population but not the presence of coronary endothelial dysfunction.

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

Background

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

Methods

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

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

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

Results

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

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

Conclusion

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

Systemic inflammation in childhood obesity: circulating inflammatory mediators and activated CD14++ monocytes

AIMS/HYPOTHESIS

In adults, circulating inflammatory mediators and activated CD14(++) monocytes link obesity to its metabolic and cardiovascular complications. However, it is largely unknown whether these inflammatory changes already occur in childhood obesity. To survey inflammatory changes during the early stages of obesity, we performed a comprehensive analysis of circulating inflammatory mediators, monocyte populations and their function in childhood obesity.

METHODS

In lean and obese children aged 6 to 16 years (n = 96), 35 circulating inflammatory mediators including adipokines were measured. Hierarchical cluster analysis of the inflammatory mediator profiles was performed to investigate associations between inflammatory mediator clusters and clinical variables. Whole-blood monocyte phenotyping and functional testing with the toll-like receptor 4 ligand, lipopolysaccharide, were also executed.

RESULTS

First, next to leptin, the circulating mediators chemerin, tissue inhibitor of metalloproteinase 1, EGF and TNF receptor 2 were identified as novel inflammatory mediators that are increased in childhood obesity. Second, cluster analysis of the circulating mediators distinguished two obesity clusters, two leanness clusters and one mixed cluster. All clusters showed distinct inflammatory mediator profiles, together with differences in insulin sensitivity and other clinical variables. Third, childhood obesity was associated with increased CD14(++) monocyte numbers and an activated phenotype of the CD14(++) monocyte subsets.

CONCLUSIONS/INTERPRETATION

Inflammatory mediator clusters were associated with insulin resistance in obese and lean children. The activation of CD14(++) monocyte subsets, which is associated with increased development of atherosclerosis in obese adults, was also readily detected in obese children. Our results indicate that inflammatory mechanisms linking obesity to its metabolic and cardiovascular complications are already activated in childhood obesity.

RGD-peptide lunasin inhibits Akt-mediated NF-κB activation in human macrophages through interaction with the αVβ3 integrin

SCOPE

Cardiovascular disease is the leading cause of mortality in the United States and regulation of aberrant macrophage activity under inflammatory conditions is critical for its prevention. The objective was to determine the effect of lunasin on the inhibition of Akt-mediated activation of nuclear factor-kappa B (NF-κB)-dependent markers of inflammation and to characterize the physical interaction of lunasin with the αVβ3 integrin receptor in lipopolysaccharide (LPS)-induced human THP-1 macrophages.

METHODS AND RESULTS

The effect of lunasin was evaluated in vitro in LPS-induced THP-1 human macrophages using immunoassays, co-immunoprecipitation (Co-IP), and fluorescence confocal microscopy. Lunasin (50 μM) reduced cyclooxygenase-2, inducible nitric oxide synthase, and NO levels by 57.9, 64.5, and 76.2%, respectively, and inhibited the activation of phosphorylated Akt and NF-κB p65 by 59.5 and 74.5%, respectively. Lunasin (50 μM) reduced exogenous release of prostaglandin E(2) and tumor necrosis factor-α by 92.5 and 94.9%, respectively. Vitronectin (10 μg/mL), an integrin ligand, increased expression of proinflammatory markers, whereas lunasin (50 μM) attenuated them. Co-IP of lunasin-treated cells confirmed direct interaction with αVβ3 integrin and LC/MS/MS verified its identity. Lunasin was detected within intracellular vesicles and reduced total αVβ3 intensity as observed by fluorescence microscopy.

CONCLUSION

Lunasin inhibited αVβ3 integrin-mediated proinflammatory markers and downregulated Akt-mediated NF-κB pathways through interaction with αVβ3 integrin.