Expression of heat shock protein-70 by dendritic cells in the arterial intima and its potential significance in atherogenesis

Deciphering the circulating immunological landscape of thoracic aortic aneurysm: Insights from a two-sample Mendelian randomization study

Background

Thoracic Aortic Aneurysm (TAA) poses significant health risks due to aortic dilation. Recent evidence suggests a pivotal role for the immune-inflammatory response in the mechanism of aortic aneurysm formation. In this study, we aim to investigate the causal relationship between circulating immune cells and TAA.

Methods

This study employs a two-sample Mendelian Randomization (MR) approach, utilizing genome-wide association study (GWAS) summary statistics for 731 immune cell types and two TAA data from large-scale studies. Causal effects of both peripheral immune cells on TAA and TAA on peripheral immune cells are explored. To ensure more accurate results, we intersected the findings from two TAA data from large-scale studies, excluding results where the direction of the odds ratio (OR) was inconsistent.

Findings

The study identifies specific immune cells associated with TAA. Notably, CD45+ NKT cell (OR: 0.95, 95CI%: 0.90-0.99 in FinnGen study; OR: 0.91, 95CI%: 0.84-0.99 in CHIP + MGI study) and CD45+ HLA-DR + CD8+ T cells (OR: 0.95, 95CI%: 0.90-0.99 in FinnGen study; OR: 0.90, 95CI%: 0.82-0.99 in CHIP + MGI study) demonstrate a protective role against TAA. In addition, CD28+ CD45RA- CD8+ T cells (relative cell counts and absolute cell counts) and HVEM + CM + CD8+ T cells are adversely affected by TAA.

Interpretation

The findings indicate that the potential protective influence exerted by specific subsets of peripheral NKT cells and CD8+ T cells in mitigating the development of TAA, while simultaneously highlighting the reciprocal effects of TAA on peripheral Treg cells subsets and T cell subsets. The complex interaction between immune cells and TAA could provide valuable clues for earlier detection and more efficacious treatment strategies for TAA.

Functional role of Ash2l in oxLDL induced endothelial dysfunction and atherosclerosis

Endothelial injury and dysfunction in the artery wall fuel the process of atherosclerosis. As a key epigenetic regulator, Ash2l (Absent, small, or homeotic-Like 2) is involved in regulating vascular injury and its complications. However, the role of Ash2l in atherosclerosis has not yet been fully elucidated. Here, we found increased Ash2l expression in high-cholesterol diet-fed ApoE-/- mice and oxidized LDL (oxLDL) treated endothelial cells (ECs). Furthermore, Ash2l promoted the scavenger receptors transcription by catalyzing histone H3 lysine 4 (H3K4) trimethylation at the promoter region of transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) and triggered the activation of the pro-inflammatory nuclear factor-kappa B (NF-κB) by enhancing interaction between CD36 and toll-like receptor 4 (TLR4). Meanwhile, enhanced expression of scavenger receptors drove more oxLDL uptake by ECs. In vivo studies revealed that ECs-specific Ash2l knockdown reduced atherosclerotic lesion formation and promoted fibrous cap stability in the aorta of ApoE-/- mice, which was partly associated with a reduced endothelial activation by suppressing scavenger receptors and the uptake of lipids by ECs. Collectively, our findings identify Ash2l as a novel regulator that mediates endothelial injury and atherosclerosis. Targeting Ash2l may provide valuable insights for developing novel therapeutic candidates for atherosclerosis.

The Role of Extracellular Heat Shock Proteins in Cardiovascular Diseases

In the early 1960s, heat shock proteins (HSPs) were first identified as vital intracellular proteinaceous components that help in stress physiology and reprogram the cellular responses to enable the organism's survival. By the early 1990s, HSPs were detected in extracellular spaces and found to activate gamma-delta T-lymphocytes. Subsequent investigations identified their association with varied disease conditions, including autoimmune disorders, diabetes, cancer, hepatic, pancreatic, and renal disorders, and cachexia. In cardiology, extracellular HSPs play a definite, but still unclear, role in atherosclerosis, acute coronary syndromes, and heart failure. The possibility of HSP-targeted novel molecular therapeutics has generated much interest and hope in recent years. In this review, we discuss the role of Extracellular Heat Shock Proteins (Ec-HSPs) in various disease states, with a particular focus on cardiovascular diseases.

Emerging role of heat shock proteins in cardiovascular diseases

Heat Shock Proteins (HSPs) are evolutionarily conserved proteins from prokaryotes to eukaryotes. They are ubiquitous proteins involved in key physiological and cellular pathways (viz. inflammation, immunity and apoptosis). Indeed, the survivability of the cells under various stressful conditions depends on appropriate levels of HSP expression. There is a growing line of evidence for the role of HSPs in regulating cardiovascular diseases (CVDs) (viz. hypertension, atherosclerosis, atrial fibrillation, cardiomyopathy and heart failure). Furthermore, studies indicate that a higher concentration of circulatory HSP antibodies correlate to CVDs; some are even potential markers for CVDs. The multifaceted roles of HSPs in regulating cellular signaling necessitate unraveling their links to pathophysiology of CVDs. This review aims to consolidate our understanding of transcriptional (via multiple transcription factors including HSF-1, NF-κB, CREB and STAT3) and post-transcriptional (via microRNAs including miR-1, miR-21 and miR-24) regulation of HSPs. The cytoprotective nature of HSPs catapults them to the limelight as modulators of cell survival. Yet another attractive prospect is the development of new therapeutic strategies against cardiovascular diseases (from hypertension to heart failure) by targeting the regulation of HSPs. Moreover, this review provides insights into how genetic variation of HSPs can contribute to the manifestation of CVDs. It would also offer a bird's eye view of the evolving role of different HSPs in the modulation and manifestation of cardiovascular disease.

The Value of SIRT1/FOXO1 Signaling Pathway in Early Detection of Cardiovascular Risk in Children with β-Thalassemia Major

Background: Atherosclerosis represents one of the major causes of morbidity in children with β-thalassemia major (β-TM). Aim: This study was designed to investigate SIRT1-FOXO1 signaling in β-TM children and their role in early detection of premature atherosclerosis. Methods: We equally subdivided 100 Egyptian children aged 6−14 years with β-TM according to carotid intima media thickness (CIMT) into 50 with CIMT < 0.5 mm and 50 with CIMT ≥ 0.5 mm, and 50 healthy children of matched age were included. They were subjected to evaluation of SIRT1, heat shock protein 72 (HSP72), and hepcidin levels via ELISA and forkhead box protein 1 (FOXO1) mRNA expression using real-time PCR in PBMCs; meanwhile, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase activities were evaluated spectrophotometrically. Results: Our results show significantly high values for CIMT, β-stiffness, atherogenic index of plasma (AIP), MDA, HSP72 and FOXO1, ferritin with significantly low hepcidin, SOD, catalase, and SIRT1 in β-TM as compared to controls with a more significant difference in β-TM with CIMT ≥ 0.5 mm than those with CIMT < 0.5 mm. A significant positive correlation between CIMT and MDA, HSP72, and FOXO1 gene expression was found, while a significant negative correlation with hepcidin, SOD, catalase, and SIRT1 was found. FOXO1 gene expression and HSP72 levels were the strongest independent determinants of CIMT. Conclusion: In β-TM, FOXO1 signaling is activated with low levels of SIRT1, and this is attributed to accelerated atherosclerosis in β-TM, which would be crucial in prediction of atherosclerosis.

Role of 72-kDa Heat Shock Protein in Heat-stimulated Regeneration of Injured Muscle in Rat

The regeneration of injured muscles is facilitated by intermittent heat stress. The 72-kDa heat shock protein (HSP72), the level of which is increased by heat stress, is likely involved in this effect, but the precise mechanism remains unclear. This study was conducted to investigate the localization and role(s) of HSP72 in the regenerating muscles in heat-stressed rats using immunohistochemistry. Heat stress was applied by immersion of the rat lower body into hot water (42C, 30 min, every other day) following injection of bupivacaine into the soleus muscles. After 1 week, we found that HSP72 was expressed at high levels not only in the surviving myofibers but also in the blood vessels of the regenerating muscles in heated rats. In addition, leukocytes, possibly granulocytes, expressing cluster of differentiation 43 within the blood capillaries surrounding the regenerating myofibers also highly expressed HSP72. In contrast, marked expression of HSP72 was not observed in the intact or regenerating muscles without heat stress. These results suggest that heat-stress-induced HSP72 within the myofibers, blood vessels, and circulating leukocytes may play important roles in enhancing regeneration of injured muscles by heat stress. Our findings would be useful to investigate cell-specific role(s) of HSP72 during skeletal muscle regeneration.

Human Invariant NKT Cells Induce IL-1β Secretion by Peripheral Blood Monocytes via a P2X7-Independent Pathway

The cytokine IL-1β plays a central role in inflammatory responses that are initiated by microbial challenges, as well as in those that are due to endogenous processes (often called sterile inflammation). IL-1β secretion that occurs independently of microbial stimulation is typically associated with the presence of endogenous alarmins, such as extracellular ATP (an indicator of cytopathic damage). In this study, we show that IL-2-activated human invariant NKT (iNKT) cells stimulate the secretion of IL-1β protein by human peripheral blood monocytes in a manner that requires neither the presence of microbial compounds nor signaling through the extracellular ATP receptor P2X7 Monocyte IL-1β production was specifically induced by iNKT cells, because similarly activated polyclonal autologous T cells did not have this effect. Secretion of IL-1β protein occurred rapidly (within 3-4 h) and required cell contact between the iNKT cells and monocytes. Similar to IL-1β production induced by TLR stimulation, the iNKT-induced pathway appeared to entail a two-step process involving NF-κB signaling and IL1B gene transcription, as well as assembly of the NLRP3 inflammasome and activation of caspase-1. However, in contrast to the classical inflammasome-mediated pathway of IL-1β production, activation of monocytes via P2X7 was dispensable for iNKT-induced IL-1β secretion, and potassium efflux was not required. Moreover, the iNKT-induced effect involved caspase-8 activity, yet it induced little monocyte death. These results suggest that IL-2-activated human iNKT cells induce monocytes to produce IL-1β through a distinctive pathway that does not require the presence of microbial danger signals or alarmins associated with cytopathic damage.

Role of Dendritic Cells in Atherosclerosis

Atherosclerosis is a lipid-related chronic inflammatory disease in which immune mechanisms play a pivotal role. The lesions are filled with large numbers of immune cells. During the last decade, dendritic cells have been identified in atherosclerotic plaques and are thought to play an important role in atherogenesis. Dendritic cells express major histocompatibility complex I and II, human leukocyte antigen-DR, CD1a, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and co-stimulatory molecule on their surfaces and this explains their unique ability to activate naive T cells. Factors such as oxidized low-density lipoprotein, hypoxia, nicotine, heat shock proteins, and altered nitric oxide synthase activity of the endothelium, all of which cause endothelial dysfunction, have a significant impact on dendritic cell adherence to endothelium and maturation. Mature dendritic cells are capable of presenting antigens to T cells, and activation of T cells leads to release of cytokines, which play an important role in the progression of disease. Drugs such as statins and diltiazem have been shown to protect endothelial function by inhibition of dendritic cell-endothelial cell interaction, and can be applied to delay the progression of cardiovascular diseases.

The role of heat shock proteins in atherosclerosis

Atherosclerosis is a chronic, multifactorial disease that starts in youth, manifests clinically later in life, and can lead to myocardial infarction, stroke, claudication, and death. Although inflammatory processes have long been known to be involved in atherogenesis, interest in this subject has grown in the past 30-40 years. Animal experiments and human analyses of early atherosclerotic lesions have shown that the first pathogenic event in atherogenesis is the intimal infiltration of T cells at arterial branching points. These T cells recognize heat shock protein (HSP)60, which is expressed together with adhesion molecules by endothelial cells in response to classic risk factors for atherosclerosis. Although these HSP60-reactive T cells initiate atherosclerosis, antibodies to HSP60 accelerate and perpetuate the disease. All healthy humans develop cellular and humoral immunity against microbial HSP60 by infection or vaccination. Given that prokaryotic (bacterial) and eukaryotic (for instance, human) HSP60 display substantial sequence homology, atherosclerosis might be the price we pay for this protective immunity, if risk factors stress the vascular endothelial cells beyond physiological conditions.

Endothelial dysfunction in tristetraprolin-deficient mice is not caused by enhanced tumor necrosis factor-α expression

Cardiovascular events are important co-morbidities in patients with chronic inflammatory diseases like rheumatoid arthritis. Tristetraprolin (TTP) regulates pro-inflammatory processes through mRNA destabilization and therefore TTP-deficient mice (TTP(-/-) mice) develop a chronic inflammation resembling human rheumatoid arthritis. We used this mouse model to evaluate molecular signaling pathways contributing to the enhanced atherosclerotic risk in chronic inflammatory diseases. In the aorta of TTP(-/-) mice we observed elevated mRNA expression of known TTP targets like tumor necrosis factor-α (TNF-α) and macrophage inflammatory protein-1α, as well as of other pro-atherosclerotic mediators, like Calgranulin A, Cathepsin S, and Osteopontin. Independent of cholesterol levels TTP(-/-) mice showed a significant reduction of acetylcholine-induced, nitric oxide-mediated vasorelaxation. The endothelial dysfunction in TTP(-/-) mice was associated with increased levels of reactive oxygen and nitrogen species (RONS), indicating an enhanced nitric oxide inactivation by RONS in the TTP(-/-) animals. The altered RONS generation correlates with increased expression of NADPH oxidase 2 (Nox2) resulting from enhanced Nox2 mRNA stability. Although TNF-α is believed to be a central mediator of inflammation-driven atherosclerosis, genetic inactivation of TNF-α neither improved endothelial function nor normalized Nox2 expression or RONS production in TTP(-/-) animals. Systemic inflammation caused by TTP deficiency leads to endothelial dysfunction. This process is independent of cholesterol and not mediated by TNF-α solely. Thus, other mediators, which need to be identified, contribute to enhanced cardiovascular risk in chronic inflammatory diseases.

IL-10 is significantly involved in HSP70-regulation of experimental subretinal fibrosis

Subretinal fibrosis is directly related to severe visual loss, especially if occurs in the macula, and is frequently observed in advanced age-related macular degeneration and other refractory eye disorders such as diabetic retinopathy and uveitis. In this study, we analyzed the immunosuppressive mechanism of subretinal fibrosis using the novel animal model recently demonstrated. Both TLR2 and TLR4 deficient mice showed significant enlargement of subretinal fibrotic area as compared with wild-type mice. A single intraocular administration of heat shock protein 70 (HSP70), which is an endogenous ligand for TLR2 and TLR4, inhibited subretinal fibrosis in wild-type mice but not in TLR2 and TLR4-deficient mice. Additionally, HSP70 induced IL-10 production in eyes from wild-type mice but was impaired in both TLR2- and TLR4-deficient mice, indicating that HSP70-TLR2/TLR4 axis plays an immunomodulatory role in subretinal fibrosis. Thus, these results suggest that HSP70-TLR2/TLR4 axis is a new therapeutic target for subretinal fibrosis due to prognostic CNV.

High glucose induces upregulation of scavenger receptors and promotes maturation of dendritic cells

BACKGROUND

Both hyperglycaemia and dendritic cells (DCs) play causative roles in atherosclerosis. However, whether they interact in atherosclerosis remains uncertain. Therefore, we examined whether high glucose could regulate the expression of scavenger receptors responsible for oxidised low-density lipoprotein (oxLDL) uptake in DCs, a critical step in atherogenesis. In addition, we investigated the impact of glucose on DC maturation regarding changes in phenotype and cytokine secretion.

METHODS

Immature DCs were cultured with different concentrations of glucose (5.5 mmol/L, 15 mmol/L, 30 mmol/L) in the absence or presence of N-acetylcysteine (NAC), SB203580 or Bay11-7082 for 24 hours. We used 30 mmol/L mannitol as a high-osmolarity control treatment. The expression of the scavenger receptors SR-A, CD36 and LOX-1 was determined by real-time PCR and western blot analysis. Furthermore, DCs were incubated with DiI-labelled oxLDL. The DiI-oxLDL-incorporated fraction was investigated by flow cytometry analysis. The intracellular production of ROS in DCs was measured by dichlorodihydrofluorescein (DCF) fluorescence using confocal microscopy. Finally, flow cytometry analysis was used to investigate immunophenotypic protein expression (CD83 and CD86). Supernatant cytokine measurements were used for immune function assays.

RESULTS

The incubation of DCs with glucose enhanced, in a dose-dependent manner, the gene and protein expression of SR-A, CD36 and LOX-1. This effect was partially abolished by NAC, SB203580 and Bay11-7082. Incubation of DCs with mannitol (30 mmol/L) did not enhance these scavenger receptors' expression. High glucose upregulated the production of ROS and expression of p38 MAPK in DCs. NAC partially reversed p38 MAPK upregulation. High glucose increased the oxLDL-uptake capacity of DCs. Blockage of the scavenger receptors SR-A and CD36 reduced oxLDL uptake, but blockage of LOX-1 did not. Furthermore, high-glucose (15 mmol/L or 30 mmol/L) treatment increased CD86 and CD83 in DCs. High glucose also increased IL-6 and IL-12 secretion and decreased IL-10 secretion.

CONCLUSION

High glucose can increase the expression of the scavenger receptors SR-A, CD36 and LOX-1, which can increase the oxLDL-uptake capacity of DCs. High glucose induces a proinflammatory cytokine profile in human DCs, leading to DC maturation. These results support the hypothesis that atherosclerosis is aggravated by hyperglycaemia-induced DC activation and oxLDL uptake.

Evidence on the pathogenic role of auto-antibodies in acute cardiovascular diseases

Atherothrombosis is the major determinant of acute ischaemic cardiovascular events, such as myocardial infarction and stroke. Inflammatory processes have been linked to all phases of atherogenesis In particular, the identification of autoimmunity mediators in the complex microenvironment of chronic inflammation has become the focus of attention in both early and advanced atherogenic processes. Auto-antibodies against self-molecules or new epitopes generated by oxidative processes infiltrate atherosclerotic plaques and were shown to modulate the activity of immune cells by binding various types of receptors. However, despite mounting evidence for a pathophysiological role of autoantibodies in atherothrombosis, the clinical relevance for circulating autoantibodies in cardiovascular outcomes is still debated. This review aims at illustrating the mechanisms by which different types of autoantibodies might either promote or repress atherothrombosis and to discuss the clinical studies assessing the role of auto-antibodies as prognostic biomarkers of plaque vulnerability.

Heat shock proteins: pathogenic role in atherosclerosis and potential therapeutic implications

Heat shock proteins (HSPs) are a highly conserved group of proteins that are constitutively expressed and function as molecular chaperones, aiding in protein folding and preventing the accumulation of misfolded proteins. In the arterial wall, HSPs have a protective role under normal physiologic conditions. In disease states, however, HSPs expressed on the vascular endothelial cell surface can act as targets for detrimental autoimmunity due to their highly conserved sequences. Developing therapeutic strategies for atherosclerosis based on HSPs is challenged by the need to balance such physiologic and pathologic roles of these proteins. This paper summarizes the role of HSPs in normal vascular wall processes as well as in the development and progression of atherosclerosis. The potential implications of HSPs in clinical therapies for atherosclerosis are also discussed.

Dendritic cells and regulatory T cells in atherosclerosis

Although macrophages and other immune system cells, especially T cells, have been shown to play disease-promoting roles in atherosclerosis, less is known about the role of antigen presenting cells. Functional, immune stimulating dendritic cells (DCs) have recently been detected in aortic intima, the site of origin of atherosclerosis. We had compared DCs with macrophages in mice with experimental atherosclerosis, to clearly define cell types by developmental and functional criteria. This review summarizes recent advances in studies of DCs in humans and in mouse models of atherosclerosis, as well as providing a simple strategy to measure regulatory T (Treg) cells in the mouse aorta.

Microbial carriage state of peripheral blood dendritic cells (DCs) in chronic periodontitis influences DC differentiation, atherogenic potential

The low-grade oral infection chronic periodontitis (CP) has been implicated in coronary artery disease risk, but the mechanisms are unclear. In this study, a pathophysiological role for blood dendritic cells (DCs) in systemic dissemination of oral mucosal pathogens to atherosclerotic plaques was investigated in humans. The frequency and microbiome of CD19(-)BDCA-1(+)DC-SIGN(+) blood myeloid DCs (mDCs) were analyzed in CP subjects with or without existing acute coronary syndrome and in healthy controls. FACS analysis revealed a significant increase in blood mDCs in the following order: healthy controls < CP < acute coronary syndrome/CP. Analysis of the blood mDC microbiome by 16S rDNA sequencing showed Porphyromonas gingivalis and other species, including (cultivable) Burkholderia cepacia. The mDC carriage rate with P. gingivalis correlated with oral carriage rate and with serologic exposure to P. gingivalis in CP subjects. Intervention (local debridement) to elicit a bacteremia increased the mDC carriage rate and frequency in vivo. In vitro studies established that P. gingivalis enhanced by 28% the differentiation of monocytes into immature mDCs; moreover, mDCs secreted high levels of matrix metalloproteinase-9 and upregulated C1q, heat shock protein 60, heat shock protein 70, CCR2, and CXCL16 transcripts in response to P. gingivalis in a fimbriae-dependent manner. Moreover, the survival of the anaerobe P. gingivalis under aerobic conditions was enhanced when within mDCs. Immunofluorescence analysis of oral mucosa and atherosclerotic plaques demonstrate infiltration with mDCs, colocalized with P. gingivalis. Our results suggest a role for blood mDCs in harboring and disseminating pathogens from oral mucosa to atherosclerosis plaques, which may provide key signals for mDC differentiation and atherogenic conversion.

Molecular chaperones and heat shock proteins in atherosclerosis

In response to stress stimuli, mammalian cells activate an ancient signaling pathway leading to the transient expression of heat shock proteins (HSPs). HSPs are a family of proteins serving as molecular chaperones that prevent the formation of nonspecific protein aggregates and assist proteins in the acquisition of their native structures. Physiologically, HSPs play a protective role in the homeostasis of the vessel wall but have an impact on immunoinflammatory processes in pathological conditions involved in the development of atherosclerosis. For instance, some members of HSPs have been shown to have immunoregulatory properties and modification of innate and adaptive response to HSPs, and can protect the vessel wall from the disease. On the other hand, a high degree of sequence homology between microbial and mammalian HSPs, due to evolutionary conservation, carries a risk of misdirected autoimmunity against HSPs expressed on the stressed cells of vascular endothelium. Furthermore, HSPs and anti-HSP antibodies have been shown to elicit production of proinflammatory cytokines. Potential therapeutic use of HSP in prevention of atherosclerosis involves achieving optimal balance between protective and immunogenic effects of HSPs and in the progress of research on vaccination. In this review, we update the progress of studies on HSPs and the integrity of the vessel wall, discuss the mechanism by which HSPs exert their role in the disease development, and highlight the potential clinic translation in the research field.

Dendritic cells in human atherosclerosis: from circulation to atherosclerotic plaques

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

Atherosclerosis induced by arsenic in drinking water in rats through altering lipid metabolism

Arsenic in drinking water is a global environmental health problem, and the exposure may increase cardiovascular and cerebrovascular diseases mortalities, most likely through causing atherosclerosis. However, the mechanism of atherosclerosis formation after arsenic exposure is still unclear. To study the mechanism of atherosclerosis formation after arsenic exposure and explore the role of high cholesterol diet (HCD) in this process, we fed spontaneous hypertensive rats and Wistar Kyoto rats with basal diet or HCD and provided with them drinking water containing arsenic at different ages and orders for 20 consecutive weeks. We measured high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), total cholesterol, triglycerides, heat shock protein 70 (HSP 70), and high sensitive C-reactive protein (hs-CRP) at predetermined intervals and determined expressions of cholesteryl ester transfer protein-1 (CETP-1) and liver X receptor β (LXRβ) in the liver. Atherosclerosis was determined by examining the aorta with hematoxylin and eosin stain. After 20 weeks, we found arsenic, alone or combined with HCD, may promote atherosclerosis formation with transient increases in HSP 70 and hs-CRP. Early combination exposure decreased the HDL-C/LDL-C ratio without changing the levels of total cholesterol and triglyceride until 30 weeks old. Both CETP-1 and LXRβ activities were suppressed, most significantly in early combination exposure. In conclusion, arsenic exposure may induce atherosclerosis through modifying reverse cholesterol transport in cholesterol metabolism and suppressing LXRβ and CEPT-1 expressions. For decreasing atherosclerosis related mortality associated with arsenic, preventing exposure from environmental sources in early life is an important element.

Correlation between lipid deposition, immune-inflammatory cell content and MHC class II expression in diffuse intimal thickening of the human aorta

Inflammatory reactions driven by an accumulation in the intima of immune-inflammatory cells and focal lipid depositions are the hallmarks of atherogenesis. It is commonly accepted that immune-inflammatory cell accumulation and lipid deposition are associated with the very earlier stage of atherosclerosis but no study has yet focused on the determination of quantitative values of this association. The present study examined correlations between lipid deposition, immune-inflammatory cell content and major histocompatibility complex (MHC) class II molecule HLA-DR expression in diffuse intimal thickening (DIT), which is thought to represent the earliest macroscopic manifestation of atherosclerosis. In parallel consecutive tissue sections of DIT, lipids were examined by chromatographic analysis (including triglycerides, cholesteryl esters, free cholesterol and phospholipids), histochemically, using Oil Red O staining, and by electron microscopy. Immune-inflammatory cells and HLA-DR expression were examined immunohistochemically in consecutive sections of the same tissue specimens. The study revealed that lipids exhibited a non-uniform distribution throughout the intima. In the juxtaluminal sublayer, lipids were localized both intracellularly and extracellularly, whereas in the juxtamedial musculoelastic sublayer, lipids were present predominantly along elastic fibers. Lipid deposits were found to positively correlate with HLA-DR expression (r=0.79; p<0.001). The study also identified a positive correlation between lipid deposition and immune-inflammatory cell content but the correlation values varied between different sublayers of the tunica intima. The correlation between lipid deposition and immune-inflammatory cell content in the juxtaluminal sublayer of the intima was notably stronger (r=0.69; p<0.001) than in the juxtamedial musculoelastic layer (r=0.28; p<0.001). The findings of the present study support a view that lipid accumulation in the intima plays a role in the initiation of inflammatory reaction and that at the pre-lesional stage in the development of atherosclerosis, lipid-associated immune cell activation might occur primarily in the juxtaluminal portion of the intima.

Serum level of soluble Hsp70 is associated with vascular calcification

It has been previously reported that serum levels of 70-kDa heat shock protein (Hsp70) are elevated in peripheral artery disease. The aim of the present study was to examine whether increased serum Hsp70 levels are related to the extent of arterial calcification and standard laboratory parameters of patients with peripheral artery disease, as well as to markers of inflammation (C-reactive protein), atherosclerosis (homocysteine), and calcification (fetuin-a). One hundred eighty chronic atherosclerotic patients with significant carotid stenosis and/or lower extremity vascular disease were enrolled in this cross-sectional study. Systemic atherosclerosis and calcification was assessed by ultrasound (carotid intima-media thickness (IMT), presence of calcification at the abdominal aorta, carotid and femoral bifurcations, and aortic and mitral cardiac valves). Standard serum markers of inflammation, diabetes, renal function, ankle-brachial indexes, and traditional risk factors for atherosclerosis were noted. Serum Hsp70 levels were measured with enzyme-linked immunosorbent assay. Standard laboratory parameters (clinical chemistry), C-reactive protein (CRP), and homocysteine levels were determined by an autoanalyzer using the manufacturer's kits. Fetuin-a levels were measured by radial immunodiffusion. Patients' median age was 64 (57-71) years, 69% were men, and 34.5% had diabetes. Serum heat shock protein 70 levels were significantly higher in patients with more severe arterial calcification (p < 0.02) and showed significant positive correlations with serum bilirubin (r = 0.23, p = 0.002) and homocysteine levels (r = 0.18, p = 0.02). Serum Hsp70 did not correlate with body mass index, IMT, CRP, or fetuin-a levels in this cohort. Logistic regression analysis confirmed the association between sHsp70 and calcification score (OR, 2.189; CI, 1.156-4.144, p = 0.016) and this correlation remained significant (OR, 2.264; CI, 1.021-5.020, p = 0.044) after the adjustment for age, sex, eGFR, smoking, CRP, and homocysteine levels. Our data show that serum Hsp70 levels correlate with the severity of atherosclerosis in patients with carotid artery disease and chronic lower limb ischemia. These data support a putative role for plasma Hsp70 in the development of arterial calcification. Nevertheless, further studies are required to investigate the usefulness of circulating Hsp70 level as a marker of atherosclerotic calcification.

Widespread distribution of HLA-DR-expressing cells in macroscopically undiseased intima of the human aorta: a possible role in surveillance and maintenance of vascular homeostasis

The architectonics and cell composition of the human large arteries are not sufficiently understood. The present study is the first to undertake an analysis of the distribution and quantities of HLA-DR-expressing cells in grossly undiseased human intima using immunohistochemical and immunofluorescent analysis, complemented by the advantages of confocal microscopy. The study revealed a widespread distribution of HLA-DR-expressing cells throughout the intimal space where the cells were integrated into continuous networks via long cell processes. Numbers of HLA-DR+ cells were found to be significantly larger in the middle third of the intima than in the superficial and deep intimal portions. We speculate that a widespread distribution of HLA-DR-expressing cells in the intima of normal human aorta might play a role in the surveillance and maintenance of vascular homeostasis.

Atypical mycobacteria in a superficial femoral artery occlusion

There is indirect evidence that atherosclerosis may occur in association with bacterial infection. The authors report the case of a young woman who presented with right calf claudication caused by a short occlusion of the superficial femoral artery. Histological examination of the excised segment of artery revealed atheroma and atypical mycobacteria within adventitial caseating granulomata. The possible causes are discussed.

Porphyromonas gingivalis-dendritic cell interactions: consequences for coronary artery disease

An estimated 80 million US adults have one or more types of cardiovascular diseases. Atherosclerosis is the single most important contributor to cardiovascular diseases; however, only 50% of atherosclerosis patients have currently identified risk factors. Chronic periodontitis, a common inflammatory disease, is linked to an increased cardiovascular risk. Dendritic cells (DCs) are potent antigen presenting cells that infiltrate arterial walls and may destabilize atherosclerotic plaques in cardiovascular disease. While the source of these DCs in atherosclerotic plaques is presently unclear, we propose that dermal DCs from peripheral inflamed sites such as CP tissues are a potential source. This review will examine the role of the opportunistic oral pathogen Porphyromonas gingivalis in invading DCs and stimulating their mobilization and misdirection through the bloodstream. Based on our published observations, combined with some new data, as well as a focused review of the literature we will propose a model for how P. gingivalis may exploit DCs to gain access to systemic circulation and contribute to coronary artery disease. Our published evidence supports a significant role for P. gingivalis in subverting normal DC function, promoting a semimature, highly migratory, and immunosuppressive DC phenotype that contributes to the inflammatory development of atherosclerosis and, eventually, plaque rupture.

Anti-heat shock protein 70 autoantibody epitope changes and BD091 promotes atherosclerosis in rats

It has been previously reported that the plasma levels of autoantibodies against heat shock protein 70 (HSP70) are elevated in atherosclerosis. The aim of the present study was to elucidate whether anti-HSP70 antibodies are involved in the pathogenesis of atherosclerosis. To determine this, we chose rats as an atherosclerosis model. Titers of plasma anti-HSP70 autoantibody were determined by ELISA. After the intravenous administration of antibody into the tail, the damaged areas of aorta were stained with Evans Blue, atheromatous plaque were stained by Oil Red O, and then they were measured and quantified with AxioVision computer software. The number of macrophages ([Formula: see text]), smooth muscle cells (SMCs), and T cells were determined by immunocytochemistry. The level of anti-HSP70 IgG1 antibody was apparently increased in the AS group at the tenth week, and one hybridoma of HSP70 antibody (BD091, IgG1, recognizing C-terminal) had the same binding epitope as plasma anti-HSP70 autoantibodies. After intravenous administration, the lesion area of aorta with BD091 was significantly larger than those of IgG(mouse) and SPA-810. Moreover, injection of BD091 resulted in significant endothelium damage, followed by a greater accumulation of [Formula: see text], T cells, and SMCs in lesions than in the control. In conclusion, BD091 reaction with HSP70 expressed on arterial endothelial cells inducing endothelium damage triggers the inflammatory response in the vessel wall that accelerates atherosclerosis in rats. BD091 shares the same binding epitope with HSP70 autoantibodies. These data indicated that a specific epitope of anti-HSP70 autoantibody participated in the pathogenesis of atherosclerosis.

Dendritic cells and their role in atherogenesis

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

The Role of Immune Complexes in Atherogenesis

Atherosclerosis is now recognized as a chronic inflammatory disease and is characterized by features of inflammation at all stages of its development. It also appears to display elements of autoimmunity, and several autoantibodies including those directed against oxidized low-density lipoprotein (ox-LDL) and heat shock proteins (Hsps) have been identified in atherosclerosis. Immune complexes (ICs) may form between these antigens and autoantibodies and via Fc receptor signaling and complement activation may modulate the inflammation in atherosclerosis. Antibody isotype may direct the role that ICs play in atherogenesis, immunoglobulin G (IgG) being potentially pro-atherogenic and immunoglobulin M (IgM) playing a protective role. Therapeutic options targeting complement activation and those which are potentially Fc-receptor mediated have been investigated in animal models, though targeting Fc receptor signaling is an area that needs further investigation.

Hsp70 expression in monocytes from patients with peripheral arterial disease and healthy controls: monocyte Hsp70 in PAD

BACKGROUND

Heat shock proteins (HSP) are induced during cellular stress. Their role is to chaperone cellular proteins giving protection from denaturation and ultimately preventing cell death. Monocytes are key cells involved in atherosclerosis and are highly responsive to HSP induction. Therefore, we wished to examine monocyte Hsp70 expression and induction in patients with peripheral arterial disease (PAD) and in healthy controls.

METHODS

We measured cellular Hsp70 levels in freshly isolated monocytes and released Hsp70 levels in plasma and monocyte culture supernatants, obtained from patients with PAD and from healthy controls. We assessed the effect of statin therapy on Hsp70 levels and examined monocyte cell survival in culture with and without immunological stress.

RESULTS

Monocyte cellular Hsp70 was lower in patients with PAD compared to healthy controls (11.3 +/- 7.4 ng/10(6) cells vs 20.7 +/- 16.0 ng/10(6) cells; p < 0.001). Individuals on statin therapy from both PAD and control groups had lower monocyte Hsp70 compared to those not treated with statins. Concentrations of Hsp70 released into culture supernatants were not dependent on PAD or statin therapy. Cell survival was inversely associated with Hsp70 concentrations in culture supernatants but had no association with cellular concentrations of Hsp70.

CONCLUSIONS

Cellular Hsp70 and released Hsp70 may play different roles in monocyte health. Whilst induced Hsp70 destined for release appears to be unaffected in PAD, mechanisms responsible for cellular retention of Hsp70 may provide an area for future therapeutic targets in vascular disease.

HSP 70 and atherosclerosis--protector or activator?

BACKGROUND

Atherosclerosis and its complications represent the leading cause of morbidity and mortality. Heat shock protein 70 (HSP70) protects cellular elements from injury by reducing oxidation, inflammation and apoptosis and by refolding damaged proteins. HSP70 improves viability of stressed vascular smooth muscle cells, possibly via its chaperone functions. It has been proposed that the response mounted against bacterial HSPs results in an autoimmune reaction, which has the potential to cause complement-mediated endothelial injury, and hence accelerate atherogenesis.

OBJECTIVE

to examine the roles of HSPs in atherosclerosis.

METHODS

A literature review.

RESULTS/CONCLUSIONS

The role of HSPs in atherosclerosis is controversial. HSP60 probably acts as an autoantigen, and may trigger both cell- and antibody-mediated immune responses, while HSP70 is likely to be involved in cytoprotection. The significance of this inverse relation between HSP70 and atherosclerosis has not yet been elucidated. Whether HSPs will become therapeutic targets remains to be established.

Statins impair CD1d-mediated antigen presentation through the inhibition of prenylation

Statins are widely used as cholesterol-lowering agents that also decrease inflammation and target enzymes essential for prenylation, an important process in the activation and intracellular transport of proteins vital for a wide variety of cellular functions. Here, we report that statins impair a critical component of the innate immune response, CD1d-mediated Ag presentation. The addition of specific intermediates in the isoprenylation pathway reversed this effect, whereas specific targeting of enzymes responsible for prenylation mimicked the inhibitory effects of statins on Ag presentation by CD1d as well as MHC class II molecules. This study demonstrates the importance of isoprenylation in the regulation of Ag presentation and suggests a mechanism by which statins reduce inflammatory responses.

Oxidized high-density lipoprotein promotes maturation and migration of bone marrow derived dendritic cells from C57BL/6J mice

OBJECTIVE

To explore the influence of oxidized high-density lipoprotein (oxHDL) on the maturation and migration of bone marrow-derived dendritic cells (BMDCs) from C57BL/6J mice.

METHODS

The C57BL/6J mice bone marrow cell suspension was prepared and purified. Recombinant granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and recombinant interleukin-4 (rmIL-4) were used to promote monocytes to differentiate and suppress lymphocytes. Then 50 microg/mL oxHDL was added to stimulate BMDCs, using 50 microg/mL high-density lipoprotein (HDL) as homologous protein control, PBS as negative control, and 1 microg/mL lipopolysaccharide (LPS) as positive control. The CD86 and MHCII expression rates were detected with fluorescence-activated cell sorting (FACS). Liquid scintillation counting (LSC) was used in mixed lymphocyte reactions (MLRs) to reflect the ability of BMDCs in stimulating the proliferation of homologous T cells. Levels of cytokines IL-12 and IL-10 were detected by ELISA. The cell migration was evaluated with the transwell system.

RESULTS

Compared with PBS group, the expressions of CD86 and MHCII, counts per minute of MLRs, secretion of IL-12 and IL-10, and number of migrated cells in oxHDL group and LPS group significantly increased (all P<0.05), while the increment was less in oxHDL group than LPS group. The number of migrated cells in oxHDL group was about twice of that in HDL group.

CONCLUSION

OxHDL may promote the maturation and migration of BMDCs in vitro.

Identification of antigen-presenting dendritic cells in mouse aorta and cardiac valves

Presumptive dendritic cells (DCs) bearing the CD11c integrin and other markers have previously been identified in normal mouse and human aorta. We used CD11c promoter–enhanced yellow fluorescent protein (EYFP) transgenic mice to visualize aortic DCs and study their antigen-presenting capacity. Stellate EYFP⁺ cells were readily identified in the aorta and could be double labeled with antibodies to CD11c and antigen-presenting major histocompatability complex (MHC) II products. The DCs proved to be particularly abundant in the cardiac valves and aortic sinus. In all aortic locations, the CD11c⁺ cells localized to the subintimal space with occasional processes probing the vascular lumen. Aortic DCs expressed little CD40 but expressed low levels of CD1d, CD80, and CD86. In studies of antigen presentation, DCs selected on the basis of EYFP expression or binding of anti-CD11c antibody were as effective as DCs similarly selected from the spleen. In particular, the aortic DCs could cross-present two different protein antigens on MHC class I to CD8⁺ TCR transgenic T cells. In addition, after intravenous injection, aortic DCs could capture anti-CD11c antibody and cross-present ovalbumin to T cells. These results indicate that bona fide DCs are a constituent of the normal aorta and cardiac valves.

oxLDL uptake by dendritic cells induces upregulation of scavenger-receptors, maturation and differentiation

BACKGROUND

Several studies have proposed a pathogenic role for oxidized LDL (oxLDL) in atherosclerosis. We tested the hypothesis whether oxLDL modulates dendritic cells (DCs), since these important antigen-presenting cells have been implicated in atherogenesis. We investigated the uptake of oxLDL by DCs, the scavenger-receptors involved and the resulting changes in phenotype and cytokine-spectra. In addition, we analyzed the impact of oxLDL on the nuclear transcription factor-kappa B (NF-kappaB)-pathway.

METHODS AND RESULTS

oxLDL (10microg/ml) increased the expression of the scavenger-receptors CD205 and CD36 and decreased the mannose-receptor expression. The lectin-like oxLDL-receptor (LOX-1)-expression was not affected. The endocytotic capacity of dextran and lucifer-yellow was moderately decreased by oxLDL. Blockage of the scavenger-receptors CD36, LOX-1 and CD205 reduced oxLDL uptake. Furthermore, oxLDL induced DC-maturation and triggered differentiation of DCs in myeloid and plasmacytoid DCs. oxLDL decreased IL-10 secretion and increased IL-6 release. Finally, oxLDL induced an activation of the NF-kappaB-pathway. Inhibition of IkappaBalpha-phosphorylation diminished the oxLDL-induced DC-maturation and -differentiation.

CONCLUSION

oxLDL uptake by DCs is mediated by the scavenger-receptors LOX-1, CD36, and CD205. oxLDL induces a proinflammatory cytokine profile in human DCs leading to DC-maturation and -differentiation which can, in part, be explained by an activation of the NF-kappaB-pathway. These results support the hypothesis that vascular inflammation may be aggravated by oxLDL induced DC-activation.

Pro-inflammatory genetic background and zinc status in old atherosclerotic subjects

Inflammation and genetics are prominent mechanisms in the pathogenesis of atherosclerosis (AT) and its complications. In this review we discuss the possible impact on AT development of several genetic determinants involved in inflammation, oxidative stress and cytoprotection (IL-6, TNF-alpha, IL-10, CD14, TLR4, MT, HSP70). Genetic polymorphisms of these genes may affect a differential inflammatory response predisposing to AT. However, allelic polymorphisms of genes which increase the risk of AT frequently occur in the general population but, only adequate gene-environment-polymorphism interactions promote the onset of the disease. Zinc deficiency has been suggested as an environmental risk factor for AT. With advancing age, the incidence of zinc deficiency increases for several reasons. Among them, dietary intake, malabsorption and genetic background of inflammatory markers may be involved. A crucial contribution may also be played by increased oxidative stress which may lead to the appearance of dysfunctional proteins, including metallothioneins (MT) that are in turn involved in zinc homeostasis. The detection of candidate genes related to inflammation and promoting AT and their reciprocal influence/interaction with zinc status might allow earlier appropriate dietary interventions in genetically susceptible subjects.

HSP70 is associated with endothelial activation in placental vascular diseases

Endothelial cell injury and activation in the placenta are features of placental vascular disease (PVD). While advances in PVD have been made, the pathogenesis of this disease is still unknown. The objective of this study was to pursue potential risk factors and signal transcription pathways involved in PVD pathogenesis. Gene expression in subjects with PVD and with normal pregnancies was compared using a two-channel microarray technique. Higher expression of HSPA6 and HSPA1A was exhibited in PVD subjects. HSPA6 and HSPA1A both encode HSP70, and, therefore, we localized HSP70 expression in placental tissue. Using quantitative polymerase chain reaction (PCR) and Western blot, we observed a significant upregulation of HSP70 in both mRNA and protein levels in placental tissue and microvascular endothelial cells of PVD subjects when compared with normal pregnancies (P< 0.05). HSP70 mRNA and protein expression also correlated negatively with infant birth weight (P< 0.05). HSP70 was expressed mainly in endothelial cells and smooth muscle cells in the placental microvessels. We therefore conclude that HSP70 may mediate endothelial activation and play a role in pathogenesis of PVD.

Invariant natural killer T cells and immunotherapy of cancer

Invariant CD1d restricted natural killer T (iNKT) cells are regulatory cells that express a canonical TCR-Valpha-chain (Valpha24.Jalpha18 in humans and Valpha14.Jalpha18 in mice) which recognizes glycolipid antigens presented by the monomorphic CD1d molecule. They can secrete a wide variety of both pro-inflammatory and anti-inflammatory cytokines very swiftly upon their activation. Evidence for the significance of iNKT cells in human cancer has been ambiguous. Still, the (pre-)clinical findings reviewed here, provide evidence for a distinct contribution of iNKT cells to natural anti-tumor immune responses in humans. Furthermore, clinical phase I studies that are discussed here have revealed that the infusion of cancer patients with ligand-loaded dendritic cells or cultured iNKT cells is well tolerated. We thus underscore the potential of iNKT cell based immunotherapy in conjunction with established modalities such as surgery and radiotherapy, as adjuvant therapy against carcinomas.

Homocysteine at pathophysiological concentrations enhances binding of dendritic cells to endothelial cells mediated by DC-SIGN

Elevated plasma homocysteine (Hcy) is an independent risk factor for atherosclerosis, which is recognized as inflammatory and immune responses. The purpose of this study was to investigate the effect of Hcy on the interaction between dendritic cells (DCs) and endothelial cells (ECs) by upregulating the expression of DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) in cultured DCs. The immunophenotype of Hcy-treated DCs was monitored by flow cytometry. Then, they were coincubated with cultured human umbilical vein endothelial cells, and adhesion of DCs to ECs, and migration of DCs through an endothelial monolayer growing on the insert of a transwell plate, were assessed using a confocal microscope and a multi-detection microplate reader. The expression of DC-SIGN on Hcy-stimulated DCs was assessed by Western blot and immunofluorescence staining. The presence of Hcy did not change the phenotype of immature and mature DCs. Hcy promoted adhesion of DCs to ECs and migration in a concentration-dependent fashion. This effect was inhibited by an anti-DC-SIGN monoclonal antibody. The expression of DC-SIGN on DCs was significantly upregulated by Hcy in a concentration-dependent manner. Taken together, our results show for the first time that Hcy can potentiate the adhesion of DCs to ECs and migration by upregulating the expression of DC-SIGN on DCs, suggesting a novel role of Hcy in the pathogenesis of human vascular disease.

Potential role of dendritic cells for progression of atherosclerotic lesions

Atherosclerosis is a lipid related chronic inflammatory disease in which immune mechanisms play a pivotal part. Its lesion is filled with large numbers of immune cells. In 1995 dendritic cells (DCs) were identified in atherosclerotic plaques and thought to play an important part in atherogenesis. DCs express MHCI and ll, HLA-DR, CD1a, ICAM-1 and VCAM1 on their surfaces, and this explains their unique ability to activate naive T cells. The risk factors for atherosclerosis are the factors for DCs' activation and migration. Mature DCs are capable of presenting antigen to T cells, which play an important part in progression of disease. Statin and diltiazem have been shown to protect endothelial function by suppressing the function of DCs and play an important part in preventing atherosclerosis.

Toll-like receptor signaling and atherosclerosis

PURPOSE OF REVIEW

Chronic inflammation and disordered lipid metabolism represent hallmarks of atherosclerosis. Considerable evidence has accumulated to suggest that innate immune defense mechanisms might interact with proinflammatory pathways and exacerbate or perhaps even initiate development of arterial plaques. Until recently the preponderance of such evidence has been indirectly emerging from clinical and epidemiologic studies, with some support from experimental animal models of atherosclerosis.

RECENT FINDINGS

Recent data now directly implicate signaling by toll-like receptor 4 and the common adaptor molecule MyD88 in the pathogenesis of atherosclerosis, establishing a key link between atherosclerosis and defense against both foreign pathogens and endogenously generated inflammatory ligands.

SUMMARY

Here we briefly review these and closely related studies, highlighting areas that should provide fertile ground for future studies aimed at a more comprehensive understanding of the interplay between innate immune defense mechanisms, atherosclerosis and related vascular disorders.

Functional profile of activated dendritic cells in unstable atherosclerotic plaque

BACKGROUND

Unstable atherosclerotic plaque typically contains an infiltrate of activated macrophages and activated T cells. This study established a functional profile of plaque-residing dendritic cells (DC) to examine whether they can function as Ag-presenting cells to facilitate in situ T-cell activation.

METHODS

Carotid artery plaque tissues were collected from 19 asymptomatic and 38 symptomatic patients undergoing endarterectomy. Matched samples of normal coronary artery wall, stable nonruptured plaque, and eroded unstable plaque were harvested from patients with fatal myocardial infarction. Quantitative PCR and immunohistochemistry were used to analyze the tissues for markers of DC activation (CD83, CD86, CCL19,CCL21) and correlate them with T-cell activation (IFN-gamma,TNF-alpha).

RESULTS

Carotid artery plaques from patients with ischemic symptoms compared to asymptomatic patients were characterized by the presence of high amount of T-cells (P<0.01) and tissue production of high levels of the T-cell cytokines IFN-gamma (P=0.001) and TNF-alpha (P=0.006). Plaque tissues from patients with ischemic complications contained elevated levels of CD83 (P<0.001), a marker of DC activation, and the DC chemokines CCL19 (P=0.001) and CCL21 (P<0.02). Unstable coronary artery plaques were similarly correlated compared to carotid plaques from symptomatic patients with the accumulation of T cells (P=0.001) and the production of T cell chemokines IFN-gamma (P=0.001) and TNF-alpha (P=0.002). Immunohistochemistry confirmed the presence of CD83(+) DC in the shoulder region of unstable plaques, where they produced the T cell-attracting chemokines CCL19 and CCL21. Mapping of activated DC demonstrated close contact between mature DC and T cells expressing the activation marker CD40 ligand (CD40L).

CONCLUSION

Activated and fully mature DC are represented in the inflammatory infiltrate characteristic for unstable carotid and coronary atheroma. Such DC produce chemokines, and thus can regulate the cell traffic into the lesion. Through the expression of the costimulatory ligand CD86, plaque-residing DC can augment T-cell stimulation and provide optimal stimulation conditions for T lymphocytes, resembling the microenvironment in organized lymphoid tissues.

The role of invariant natural killer T cells in lupus and atherogenesis

Systemic lupus erythematosus (SLE) is increasingly recognized as a risk factor for the development of premature atherosclerosis. The inflammatory process in both of these diseases is controlled by a variety of cell types of the innate and adaptive immune systems. Recent studies from several groups, including ours, have revealed a critical role of a unique subset of lymphocytes, termed invariant natural killer T (iNKT) cells, in the development of lupus-like autoimmunity and atherosclerosis in animal models. iNKT cells appear to play complex and divergent roles in the development of SLE and atherosclerosis. Our findings suggest that alterations in iNKT cell functions during the development of SLE may be related to the increased risk of SLE patients to develop atherosclerosis and coronary heart disease. We found that iNKT cell activation with the sponge-derived glycolipid alpha- galactosylceramide generally protects against the development of lupus-like autoimmunity in mice, whereas it exacerbates atherosclerosis. Therefore, while our studies have identified iNKT cells as potential therapeutic targets for SLE, further studies are necessary to design drugs that will avoid the underlying harmful effects of iNKT cell activation on the development of atherosclerosis.