The role of complement in atherosclerosis

Multi-trait association analysis reveals shared genetic loci between Alzheimer's disease and cardiovascular traits

Several cardiovascular traits and diseases co-occur with Alzheimer's disease. We mapped their shared genetic architecture using multi-trait genome-wide association studies. Subsequent fine-mapping and colocalisation highlighted 16 genetic loci associated with both Alzheimer's and cardiovascular diseases. We prioritised rs11786896, which colocalised with Alzheimer's disease, atrial fibrillation and expression of PLEC in the heart left ventricle, and rs7529220, which colocalised with Alzheimer's disease, atrial fibrillation and expression of C1Q family genes. Single-cell RNA-sequencing data, co-expression network and protein-protein interaction analyses provided evidence for different mechanisms of PLEC, which is upregulated in left ventricular endothelium and cardiomyocytes with heart failure and in brain astrocytes with Alzheimer's disease. Similar common mechanisms are implicated for C1Q in heart macrophages with heart failure and in brain microglia with Alzheimer's disease. These findings highlight inflammatory and pleomorphic risk determinants for the co-occurrence of Alzheimer's and cardiovascular diseases and suggest PLEC, C1Q and their interacting proteins as potential therapeutic targets.

Proteomic Profiling of Endothelial Cell Secretomes After Exposure to Calciprotein Particles Reveals Downregulation of Basement Membrane Assembly and Increased Release of Soluble CD59

Calciprotein particles (CPPs) are essential circulating scavengers of excessive Ca2+ and PO43- ions, representing a vehicle that removes them from the human body and precludes extraskeletal calcification. Having been internalised by endothelial cells (ECs), CPPs induce their dysfunction, which is accompanied by a remarkable molecular reconfiguration, although little is known about this process's extracellular signatures. Here, we applied ultra-high performance liquid chromatography-tandem mass spectrometry to perform a secretome-wide profiling of the cell culture supernatant from primary human coronary artery ECs (HCAECs) and internal thoracic artery ECs (HITAECs) treated with primary CPPs (CPP-P), secondary CPPs (CPP-S), magnesiprotein particles (MPPs), or Ca2+/Mg2+-free Dulbecco's phosphate-buffered saline (DPBS) for 24 h. Incubation with CPP-P/CPP-S significantly altered the profiles of secreted proteins, delineating physiological and pathological endothelial secretomes. Neither pathway enrichment analysis nor the interrogation of protein-protein interactions detected extracellular matrix- and basement membrane-related molecular terms in the protein datasets from CPP-P/CPP-S-treated ECs. Both proteomic profiling and enzyme-linked immunosorbent assay identified an increased level of protectin (CD59) and reduced levels of osteonectin (SPARC), perlecan (HSPG2), and fibronectin (FN1) in the cell culture supernatant upon CPP-P/CPP-S treatment. Elevated soluble CD59 and decreased release of basement membrane components might be considered as potential signs of dysfunctional endothelium.

Efferocytosis by macrophages in physiological and pathological conditions: regulatory pathways and molecular mechanisms

Efferocytosis is defined as the highly effective phagocytic removal of apoptotic cells (ACs) by professional or non-professional phagocytes. Tissue-resident professional phagocytes ("efferocytes"), such as macrophages, have high phagocytic capacity and are crucial to resolve inflammation and aid in homeostasis. Recently, numerous exciting discoveries have revealed divergent (and even diametrically opposite) findings regarding metabolic immune reprogramming associated with efferocytosis by macrophages. In this review, we highlight the key metabolites involved in the three phases of efferocytosis and immune reprogramming of macrophages under physiological and pathological conditions. The next decade is expected to yield further breakthroughs in the regulatory pathways and molecular mechanisms connecting immunological outcomes to metabolic cues as well as avenues for "personalized" therapeutic intervention.

The relationship between complement C1q and coronary plaque vulnerability based on optical coherence tomography analysis

To determine the association between complement C1q and vulnerable plaque morphology among coronary artery disease (CAD) patients. We conducted a retrospective observational study of 221 CAD patients admitted to The Second Affiliated Hospital of Xi'an Jiaotong University. Intravascular optical coherence tomography was utilized to describe the culprit plaques' morphology. Using logistic regression analysis to explore the correlation between C1q and vulnerable plaques, and receiver operator characteristic (ROC) analysis assess the predictive accuracy. As reported, the complement C1q level was lower in ACS patients than CCS patients (18.25 ± 3.88 vs. 19.18 ± 4.25, P = 0.045). The low complement-C1q-level group was more prone to develop vulnerable plaques. In lipid-rich plaques, the complement C1q level was positively correlated with the thickness of fibrous cap (r = 0.480, P = 0.041). Univariate and multivariate logistic regression analyses suggested that complement C1q could be an independent contributor to plaques' vulnerability. For plaque rupture, erosion, thrombus, and cholesterol crystals, the areas under the ROC curve of complement C1q level were 0.873, 0.816, 0.785, and 0.837, respectively (P < 0.05 for all). In CAD patients, the complement C1q could be a valuable indicator of plaque vulnerability.

The role of immune system in atherosclerosis: Molecular mechanisms, controversies, and future possibilities

Numerous cardiovascular disorders have atherosclerosis as their pathological underpinning. Numerous studies have demonstrated that, with the aid of pattern recognition receptors, cytokines, and immunoglobulins, innate immunity, represented by monocytes/macrophages, and adaptive immunity, primarily T/B cells, play a critical role in controlling inflammation and abnormal lipid metabolism in atherosclerosis. Additionally, the finding of numerous complement components in atherosclerotic plaques suggests yet again how heavily the immune system controls atherosclerosis. Therefore, it is essential to have a thorough grasp of how the immune system contributes to atherosclerosis. The specific molecular mechanisms involved in the activation of immune cells and immune molecules in atherosclerosis, the controversy surrounding some immune cells in atherosclerosis, and the limitations of extrapolating from relevant animal models to humans were all carefully reviewed in this review from the three perspectives of innate immunity, adaptive immunity, and complement system. This could provide fresh possibilities for atherosclerosis research and treatment in the future.

Targeting Cell-Specific Molecular Mechanisms of Innate Immunity in Atherosclerosis

Mechanisms of innate immunity contribute to inflammation, one of the major underlying causes of atherogenesis and progression of atherosclerotic vessel disease. How immune cells exactly contribute to atherosclerosis and interact with molecules of cholesterol homeostasis is still a matter of intense research. Recent evidence has proposed a potential role of previously underappreciated cell types in this chronic disease including platelets and dendritic cells (DCs). The pathophysiology of atherosclerosis is studied in models with dysfunctional lipid homeostasis and several druggable molecular targets are derived from these models. Specific therapeutic approaches focussing on these immune mechanisms, however, have not been successfully introduced into everyday clinical practice, yet. This review highlights molecular insights into immune processes related to atherosclerosis and potential future translational approaches targeting these molecular mechanisms.

A Novel Immunoassay for Malondialdehyde-Conjugated Low-Density Lipoprotein Measures Dynamic Changes in the Blood of Patients Undergoing Coronary Artery Bypass Graft Surgery

Oxidized low-density lipoproteins play an important role in tissue pathology. In this study, we report a sensitive novel enzyme-linked immunosorbent assay for the detection of malondialdehyde-modified low-density lipoprotein (MDA-LDL), a key component of oxidized LDL. The assay is capable of measuring a variable presence of MDA-LDL within human plasma and serum. We demonstrate the robust nature of the assay on samples stored for over 20 months, as well as high inter-operator reproducibility (r = 0.74, p < 0.0001). The assay was capable of detecting dynamic changes in patient blood samples after coronary artery bypass graft surgery, indicating synthesis or release of MDA-LDL with the oxidative stress of surgery, followed by homeostatic clearance. This robust, sensitive and specific assay for circulating MDA-LDL will serve as a valuable translational tool for the improved detection of oxidative forms of LDL in response to a range of physiological or pathological stimuli, with potential clinical applicability.

Circulating Extracellular Vesicle Proteins and MicroRNA Profiles in Subcortical and Cortical-Subcortical Ischaemic Stroke

In order to investigate the role of circulating extracellular vesicles (EVs), proteins, and microRNAs as damage and repair markers in ischaemic stroke depending on its topography, subcortical (SC), and cortical-subcortical (CSC) involvement, we quantified the total amount of EVs using an enzyme-linked immunosorbent assay technique and analysed their global protein content using proteomics. We also employed a polymerase chain reaction to evaluate the circulating microRNA profile. The study included 81 patients with ischaemic stroke (26 SC and 55 CSC) and 22 healthy controls (HCs). No differences were found in circulating EV levels between the SC, CSC, and HC groups. We detected the specific expression of C1QA and Casp14 in the EVs of patients with CSC ischaemic stroke and the specific expression of ANXA2 in the EVs of patients with SC involvement. Patients with CSC ischaemic stroke showed a lower expression of miR-15a, miR-424, miR-100, and miR-339 compared with those with SC ischaemic stroke, and the levels of miR-339, miR-100, miR-199a, miR-369a, miR-424, and miR-15a were lower than those of the HCs. Circulating EV proteins and microRNAs from patients with CSC ischaemic stroke could be considered markers of neurite outgrowth, neurogenesis, inflammation process, and atherosclerosis. On the other hand, EV proteins and microRNAs from patients with SC ischaemic stroke might be markers of an anti-inflammatory process and blood–brain barrier disruption reduction.

Serum Complement C1q Activity Is Associated With Obstructive Coronary Artery Disease

Background: Complement C1q plays a dual role in the atherosclerosis. Previous studies showed inconsistent results about the association of serum C1q levels and coronary artery disease (CAD). Here, we explored the associations of serum C1q activity with CAD, coronary stenosis severity, cardiovascular biomarkers, and 1-year restenosis after coronary artery revascularization.

Methods: We enrolled 956 CAD patients and 677 controls to evaluate the associations of serum complement C1q activity to the presence and severity of obstructive CAD and non-obstructive CAD. Serum C1q activity and the concentrations of laboratory markers were measured in all subjects. All the data were analyzed using SPSS22.0 software.

Results: Serum C1q activity in Obstructive CAD and Non-Obstructive CAD groups was significantly higher than the control group (195.52 ± 48.31 kU/L and 195.42 ± 51.25 kU/L vs. 183.44 ± 31.75 kU/L, P < 0.05). Greater C1q activity was significantly correlated with higher total cholesterol (TC) and triglyceride (TG) levels. C1q activity was associated with an increased Odds Ratio (OR) of CAD (OR = 1.322, 95% CI 1.168–1.496, P < 0.05) and 1-year restenosis after revascularization (the highest OR = 3.544, 95% CI 1.089–12.702, P < 0.05). Complement C1q activity was not correlated with Gensini score in the Obstructive CAD group after adjustment for confounders. C1q activity has low value in predicting the incidence of CAD.

Conclusion: Serum complement C1q activity is associated with obstructive CAD.

Association between serum adipsin and plaque vulnerability determined by optical coherence tomography in patients with coronary artery disease

Background

Early identification of vulnerable plaques is important for patients with coronary artery disease (CAD) to reduce acute coronary events and improve their prognosis. We sought to examine the relationship between adipsin, an adipokine secreted from adipocytes, and plaque vulnerability in CAD patients.

Methods

A total of 103 plaques from 99 consecutive patients who underwent coronary angiography were assessed by optical coherence tomography. The serum level of adipsin was measured using enzyme-linked immunosorbent assay (ELISA). The accuracy of adipsin for detecting thin-cap fibroatheroma (TCFA) was determined by the area under the receiver operating characteristic curve (AUC).

Results

Of the 99 patients, 49 were classified into the low adipsin group and 50 into the high adipsin group according to the median level of serum adipsin (2.43 µg/mL). The plaques from the high adipsin group exhibited a greater lipid index (2,700.0 vs. 1,975.9° × mm, P=0.015) and an increased proportion of TCFAs (41.2% vs. 21.2%, P=0.028) compared with the low adipsin group. Serum adipsin was found to be negatively correlated with fibrous cap thickness (ρ=−0.322, P=0.002), while it was positively correlated with average lipid arc (ρ=0.253, P=0.015), maximum lipid arc (ρ=0.211, P=0.044), lipid core length (ρ=0.241, P=0.021), lipid index (ρ=0.335, P=0.001), and vulnerability score (ρ=0.254, P=0.014). Furthermore, adipsin had a significant association with TCFAs (OR: 1.290, 95% CI: 1.048–1.589, P=0.016) in the multivariate analysis, while having a moderate diagnostic accuracy for TCFAs (AUC: 0.710, 95% CI: 0.602–0.817, P<0.001).

Conclusions

Our findings suggest that serum adipsin is significantly and positively correlated with the incidence of TCFAs. The application of adipsin as a biomarker may offer improvement in the diagnosis of vulnerable plaques and clinical benefits for CAD patients.

Recombinant C1q variants modulate macrophage responses but do not activate the classical complement pathway

Complement protein C1q plays a dual role in a number of inflammatory diseases such as atherosclerosis. While in later stages classical complement pathway activation by C1q exacerbates disease progression, C1q also plays a beneficial role in early disease. Independent of its role in complement activation, we and others have identified a number of potentially beneficial interactions of C1q with phagocytes in vitro, including triggering phagocytosis of cellular and molecular debris and polarizing macrophages toward an anti-inflammatory phenotype. These interactions may also be important in preventing autoimmunity. Here, we characterize variants of recombinant human C1q (rC1q) which no longer initiate complement activation, through mutation of the C1r₂C1s₂ interaction site. For insight into the structural location of the site of C1q that is important for interaction with phagocytes, we investigated the effect of these mutations on phagocytosis and macrophage inflammatory polarization, as compared to wild-type C1q. Phagocytosis of antibody coated sheep erythrocytes and oxidized LDL was measured in human monocytes and monocyte-derived macrophages (HMDM) respectively that had interacted with rC1q wild-type or variants. Secreted levels of cytokines were also measured in C1q stimulated HMDM. All variants of C1q increased phagocytosis in HMDM compared to controls, similar to native or wild-type rC1q. In addition, levels of certain pro-inflammatory cytokines and chemokines secreted by HMDM were modulated in cells that interacted with C1q variants, similar to wild-type rC1q and native C1q. This includes downregulation of IL-1α, IL-1β, TNFα, MIP-1α, and IL-12p40 by native and rC1q in both resting and M1-polarized HMDM. This suggests that the site responsible for C1q interaction with phagocytes is independent of the C1r₂C1s₂ interaction site. Further studies with these classical pathway-null variants of C1q should provide greater understanding of the complement-independent role of C1q, and allow for potential therapeutic exploitation.

Usefulness of Complement C1q to Predict 10-Year Mortality in Men With Diabetes Mellitus Referred for Coronary Angiography

The complement system consists of a family of proteins that play a critical role in the innate immune system. Complement activation has been implicated in many chronic inflammatory diseases, including atherosclerosis. However, a number of experimental studies have highlighted a beneficial role of component C1q in early atherosclerosis and in diabetes mellitus (DM). Despite these data, there have been no studies that have specifically examined the utility of plasma complement C1q as a clinical biomarker in patients with known or suspected coronary artery disease. In this study, baseline plasma complement C1q levels were measured in 159 men with DM who were referred for coronary angiography and who were followed up prospectively for the development of all-cause mortality for 10 years. After adjustment for baseline clinical, angiographic, and laboratory parameters, reduced plasma complement C1q levels were an independent predictor of all-cause mortality at 10 years (hazard ratio 0.66, 95% confidence interval 0.52 to 0.84, p = 0.0006). In additional multivariate models that adjusted for a variety of biomarkers with established prognostic efficacy, complement C1q remained an independent predictor of all-cause mortality at 10 years. In conclusion, reduced levels of complement C1q are associated with an increased risk of all-cause mortality at 10 years in patients with DM referred for coronary angiography. Furthermore, this association is independent of a variety of clinical, angiographic, laboratory variables, including biomarkers with established prognostic efficacy in the prediction of adverse cardiovascular outcomes.

Overexpression of complement component C5a accelerates the development of atherosclerosis in ApoE-knockout mice

BACKGROUND

In this study, we investigated the direct effect of C5a overexpression on atherosclerosis.

METHODS AND RESULTS

A recombinant adenovirus expressing mouse C5a (Ad-C5a) was constructed and injected intravenously into ApoE-/- mice. After 12 weeks of a high-fat diet, Ad-C5a injection produced more extensive lesions than control adenovirus, and its proathrosclerotic role was significantly blocked by C5a receptor antagonist. Immunohistochemical analysis showed enhanced macrophage infiltration in atherosclerotic regions with C5a overexpression. Trans-well assay revealed C5a receptor-dependent chemotaxis of C5a to macrophages. Furthermore, Ad-C5a overexpression promoted foam cell formation and lipid deposition but reduced collagen content. In addition, with Ad-C5a overexpression, the serum levels of interleukin 6 and tumor necrosis factor α were upregulated.

CONCLUSIONS

C5a overexpression could accelerate the development of atherosclerosis in ApoE-/- mice by promoting macrophage recruitment, foam cell formation and inflammatory activation. Furthermore, its proatherogetic role is mediated by the C5a receptor.

Short- and Long-Term Effects of Weight Loss on the Complement Component C3 After Laparoscopic Gastric Bypass in Obese Patients

BACKGROUND

The C3 complement component (C3c) is increasingly recognized as a cardiometabolic risk factor, but how it is affected after weight loss through gastric bypass is a question yet to be answered.

METHODS

A total of 66 obese patients underwent laparoscopic gastric bypass. Anthropometric parameters, total cholesterol (TC), triglycerides, high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), glucose, insulin, HOMA-IR, liver enzymes, high-sensitivity C-reactive protein (hsCRP), and C3c levels were evaluated at baseline and at 1 and 5 years post-surgery.

RESULTS

All anthropometric and biochemical parameters improved significantly after surgery, although a deterioration was detected with respect to the percentage of excess of weight loss, insulin, TC, LDLc, and lactate dehydrogenase 5 years post-surgery. Despite this, a remission rate of 84 % was observed in the presence of metabolic syndrome after 5 years follow-up. hsCRP and C3c were reduced significantly after surgery and maintained throughout the experimental period. In addition, C3c was correlated with BMI and insulin at all time points. The multivariate regression model, in which C3c was a dependent variable, revealed that aspartate aminotransferase and BMI were independent variables at baseline, alkaline phosphatase and insulin were independent at 1 year post-surgery, and insulin, BMI, and TC were independent at 5 years post-surgery.

CONCLUSIONS

C3c may be a marker of the chronic inflammatory process underlying insulin resistance. Its association with BMI and liver enzymes supports a major role in metabolic activity, although future research is needed to clarify the nature of the molecular mechanisms involved and the physiological significance of these findings.

Differential gene expression in human abdominal aortic aneurysm and aortic occlusive disease

Abdominal aortic aneurysm (AAA) and aortic occlusive disease (AOD) represent common causes of morbidity and mortality in elderly populations which were previously believed to have common aetiologies. The aim of this study was to assess the gene expression in human AAA and AOD. We performed microarrays using aortic specimen obtained from 20 patients with small AAAs (≤ 55mm), 29 patients with large AAAs (> 55mm), 9 AOD patients, and 10 control aortic specimens obtained from organ donors. Some differentially expressed genes were validated by quantitative-PCR (qRT-PCR)/immunohistochemistry. We identified 840 and 1,014 differentially expressed genes in small and large AAAs, respectively. Immune-related pathways including cytokine-cytokine receptor interaction and T-cell-receptor signalling were upregulated in both small and large AAAs. Examples of validated genes included CTLA4 (2.01-fold upregulated in small AAA, P = 0.002), NKTR (2.37-and 2.66-fold upregulated in small and large AAA with P = 0.041 and P = 0.015, respectively), and CD8A (2.57-fold upregulated in large AAA, P = 0.004). 1,765 differentially expressed genes were identified in AOD. Pathways upregulated in AOD included metabolic and oxidative phosphorylation categories. The UCP2 gene was downregulated in AOD (3.73-fold downregulated, validated P = 0.017). In conclusion, the AAA and AOD transcriptomes were very different suggesting that AAA and AOD have distinct pathogenic mechanisms.

The complement system and toll-like receptors as integrated players in the pathophysiology of atherosclerosis

Despite recent medical advances, atherosclerosis is a global burden accounting for numerous deaths and hospital admissions. Immune-mediated inflammation is a major component of the atherosclerotic process, but earlier research focus on adaptive immunity has gradually switched towards the role of innate immunity. The complement system and toll-like receptors (TLRs), and the crosstalk between them, may be of particular interest both with respect to pathogenesis and as therapeutic targets in atherosclerosis. Animal studies indicate that inhibition of C3a and C5a reduces atherosclerosis. In humans modified LDL-cholesterol activate complement and TLRs leading to downstream inflammation, and histopathological studies indicate that the innate immune system is present in atherosclerotic lesions. Moreover, clinical studies have demonstrated that both complement and TLRs are upregulated in atherosclerotic diseases, although interventional trials have this far been disappointing. However, based on recent research showing an intimate interplay between complement and TLRs we propose a model in which combined inhibition of both complement and TLRs may represent a potent anti-inflammatory therapeutic approach to reduce atherosclerosis.

Role of complement and complement regulatory proteins in the complications of diabetes

It is well established that the organ damage that complicates human diabetes is caused by prolonged hyperglycemia, but the cellular and molecular mechanisms by which high levels of glucose cause tissue damage in humans are still not fully understood. The prevalent hypothesis explaining the mechanisms that may underlie the pathogenesis of diabetes complications includes overproduction of reactive oxygen species, increased flux through the polyol pathway, overactivity of the hexosamine pathway causing intracellular formation of advanced glycation end products, and activation of protein kinase C isoforms. In addition, experimental and clinical evidence reported in past decades supports a strong link between the complement system, complement regulatory proteins, and the pathogenesis of diabetes complications. In this article, we summarize the body of evidence that supports a role for the complement system and complement regulatory proteins in the pathogenesis of diabetic vascular complications, with specific emphasis on the role of the membrane attack complex (MAC) and of CD59, an extracellular cell membrane-anchored inhibitor of MAC formation that is inactivated by nonenzymatic glycation. We discuss a pathogenic model of human diabetic complications in which a combination of CD59 inactivation by glycation and hyperglycemia-induced complement activation increases MAC deposition, activates pathways of intracellular signaling, and induces the release of proinflammatory, prothrombotic cytokines and growth factors. Combined, complement-dependent and complement-independent mechanisms induced by high glucose promote inflammation, proliferation, and thrombosis as characteristically seen in the target organs of diabetes complications.

The pleiotropic role of HDL in autoimmune diseases

As is widely known, the classic function of HDL is reverse cholesterol transport (RCT), thus removing cholesterol from peripheral tissues. Early epidemiological studies, such as Framingham's, stated that increased HDL levels were associated with a significant decrease in relative risk for cardiovascular disease (CVD) mortality. However, those with heightened expectations in recent years for the development of therapeutic targets to increase HDL levels have been disappointed, because efforts have demonstrated the opposite effect on cardiovascular and global mortality. However, in contrast, studies have highlighted the complexity and the intriguing role of HDL in different pathological conditions, such as infections, neoplasms, and autoimmune diseases. In this review an attempt is made to summarize some biological pathways that link HDL function with the immune system, and its possible clinical repercussions in autoimmune diseases.

Placental lesions associated with acute atherosis

OBJECTIVE

Acute atherosis is a lesion of the spiral arteries characterized by fibrinoid necrosis of the vessel wall, an accumulation of fat-containing macrophages, and a mononuclear perivascular infiltrate, which can be found in patients with preeclampsia, fetal death, small-for-gestational age, spontaneous preterm labor/premature prelabor rupture of membrane, and spontaneous mid-trimester abortion. This lesion is thought to decrease blood flow to the intervillous space which may lead to other vascular lesions of the placenta. The objective of this study was to test whether there is an association between acute atherosis and placental lesions that are consistent with maternal vascular underperfusion (MVU), amniotic fluid infection (AFI), fetal vascular thrombo-occlusive disease (FVTOD) or chronic inflammation.

MATERIAL AND METHODS

A retrospective cohort study of pregnant women who delivered between July 1998 and July 2014 at Hutzel Women's Hospital/Detroit Medical Center was conducted examine 16 457 placentas. The frequency of placenta lesions (diagnosed using the criteria of the Perinatal Section of the Society for Pediatric Pathology) was compared between pregnancies with and without acute atherosis.

RESULTS

Among 16 457 women who were enrolled, 10.2% (1671/16 457) were excluded, leaving 14 786 women who contributed data for analysis. Among them, the prevalence of acute atherosis was 2.2% (326/14 786). Women with acute atherosis were more than six times as likely as those without to have placental lesions consistent with maternal underperfusion (adjusted odds ratio - aOR: 6.7; 95% CI 5.2-8.6). To a lesser degree, acute atherosis was also associated with greater risks of having either lesions consistent with FVTOD (aOR 1.7; 95% CI 1.2-2.3) or chronic chorioamnionitis (aOR 1.9; 95% CI 1.3-3), but not with other chronic inflammatory lesions, after adjusting for gestational age at delivery. In contrast, women with acute atherosis were 60% less likely to have lesions consistent with AFI, adjusting for gestational age at delivery (aOR 0.4; 95% CI 0.3-0.5).

CONCLUSIONS

Acute atherosis is associated with increased risks of having placental lesions consistent with MVU, and to a lesser extent, chronic chorioamnionitis and those consistent with FVTOD.

Complement factor C5a induces atherosclerotic plaque disruptions

Complement factor C5a and its receptor C5aR are expressed in vulnerable atherosclerotic plaques; however, a causal relation between C5a and plaque rupture has not been established yet. Accelerated atherosclerosis was induced by placing vein grafts in male apoE(-/-) mice. After 24 days, when advanced plaques had developed, C5a or PBS was applied locally at the lesion site in a pluronic gel. Three days later mice were killed to examine the acute effect of C5a on late stage atherosclerosis. A significant increase in C5aR in the plaque was detectable in mice treated with C5a. Lesion size and plaque morphology did not differ between treatment groups, but interestingly, local treatment with C5a resulted in a striking increase in the amount of plaque disruptions with concomitant intraplaque haemorrhage. To identify the potential underlying mechanisms, smooth muscle cells and endothelial cells were treated in vitro with C5a. Both cell types revealed a marked increase in apoptosis after stimulation with C5a, which may contribute to lesion instability in vivo. Indeed, apoptosis within the plaque was seen to be significantly increased after C5a treatment. We here demonstrate a causal role for C5a in atherosclerotic plaque disruptions, probably by inducing apoptosis. Therefore, intervention in complement factor C5a signalling may be a promising target in the prevention of acute atherosclerotic complications.

Complement protein C1q promotes macrophage anti-inflammatory M2-like polarization during the clearance of atherogenic lipoproteins

OBJECTIVE

Innate immune protein C1q plays a dual role in the chronic inflammatory disease of atherosclerosis. Complement activation via C1q exacerbates pathology in the atherosclerotic lesion in later stages of the disease. However, in early stages of disease C1q is protective. We hypothesize that complement-independent activities of C1q are involved in reprogramming macrophage inflammatory polarization.

METHODS

The influence of C1q on macrophage inflammatory responses during clearance of oxLDL was examined. Changes in cytokines at the gene and protein level were measured by quantitative PCR and ELISA assay.

RESULTS

C1q modulated cytokine expression in Raw264.7 macrophages during ingestion of oxLDL. Levels of pro-inflammatory cytokines IL-1β and IL-6 were downregulated by C1q, whereas levels of the anti-inflammatory cytokine IL-10 were increased. In addition, data from an NFκB-luciferase gene reporter assay suggest that C1q suppresses activation of NFκB during lipoprotein clearance in macrophages, providing one mechanism by which C1q downregulates pro-inflammatory cytokine production.

CONCLUSIONS

C1q-polarization of macrophages toward an anti-inflammatory (M2-like) phenotype may be important in dampening inflammation in the early atherosclerotic lesion. Further investigation of molecular pathways targeted by C1q may provide novel therapeutic targets for this disease.

Multiple potential roles for B cells in atherosclerosis

The development of atherosclerosis is the major etiological factor causing cardiovascular disease and constitutes a lipid-induced, chronic inflammatory and autoimmune disease of the large arteries. A long-standing view of the protective role of B cells in atherosclerosis has been challenged by recent studies using B cell depletion in animal models. Whereas complete B cell deficiency increases atherosclerosis, depletion of B2 but not B1 cells reduces atherosclerosis. This has led to a re-evaluation of the multiple potential pathways by which B cells can regulate atherosclerosis, and the apparent opposing roles of B1 and B2 cells. B cells, in addition to having the unique ability to produce antibodies, are now recognized to play a number of important roles in the immune system, including cytokine production and direct regulation of T cell responses. This review summarizes current knowledge on B cell subsets and functions, and how these could distinctly influence atherosclerosis development.

A vital role for complement in heart disease

Heart diseases are common and significant contributors to worldwide mortality and morbidity. During recent years complement mediated inflammation has been shown to be an important player in a variety of heart diseases. Despite some negative results from clinical trials using complement inhibitors, emerging evidence points to an association between the complement system and heart diseases. Thus, complement seems to be important in coronary heart disease as well as in heart failure, where several studies underscore the prognostic importance of complement activation. Furthermore, patients with atrial fibrillation often share risk factors both with coronary heart disease and heart failure, and there is some evidence implicating complement activation in atrial fibrillation. Moreover, Chagas heart disease, a protozoal infection, is an important cause of heart failure in Latin America, and the complement system is crucial for the protozoa-host interaction. Thus, complement activation appears to be involved in the pathophysiology of a diverse range of cardiac conditions. Determination of the exact role of complement in the various heart diseases will hopefully help to identify patients that might benefit from therapeutic complement intervention.

The complement system in human cardiometabolic disease

The complement system has been implicated in obesity, fatty liver, diabetes and cardiovascular disease (CVD). Complement factors are produced in adipose tissue and appear to be involved in adipose tissue metabolism and local inflammation. Thereby complement links adipose tissue inflammation to systemic metabolic derangements, such as low-grade inflammation, insulin resistance and dyslipidaemia. Furthermore, complement has been implicated in pathophysiological mechanisms of diet- and alcohol induced liver damage, hyperglycaemia, endothelial dysfunction, atherosclerosis and fibrinolysis. In this review, we summarize current evidence on the role of the complement system in several processes of human cardiometabolic disease. C3 is the central component in complement activation, and has most widely been studied in humans. C3 concentrations are associated with insulin resistance, liver dysfunction, risk of the metabolic syndrome, type 2 diabetes and CVD. C3 can be activated by the classical, the lectin and the alternative pathway of complement activation; and downstream activation of C3 activates the terminal pathway. Complement may also be activated via extrinsic proteases of the coagulation, fibrinolysis and the kinin systems. Studies on the different complement activation pathways in human cardiometabolic disease are limited, but available evidence suggests that they may have distinct roles in processes underlying cardiometabolic disease. The lectin pathway appeared beneficial in some studies on type 2 diabetes and CVD, while factors of the classical and the alternative pathway were related to unfavourable cardiometabolic traits. The terminal complement pathway was also implicated in insulin resistance and liver disease, and appears to have a prominent role in acute and advanced CVD. The available human data suggest a complex and potentially causal role for the complement system in human cardiometabolic disease. Further, preferably longitudinal studies are needed to disentangle which aspects of the complement system and complement activation affect the different processes in human cardiometabolic disease.

Cholesterol crystal-induced endothelial cell activation is complement-dependent and mediated by TNF

Cholesterol crystals are known to be a hallmark of atherosclerosis with recent studies demonstrating deposition of these crystals in early fatty streak formation as well as penetrating the intima following plaque rupture. Inflammation has also become a central focus in atheroma development and endothelial cell activation is recognized as necessary for the recruitment of inflammatory cells to the plaque. However, the extent to which cholesterol crystals can induce inflammation and activate endothelial cells is not known. To investigate this, we developed a novel model activating human umbilical vein endothelial cells using lepirudin anticoagulated human whole blood. We found that cholesterol crystals caused a marked and dose-dependent increase in the adhesion molecules E-selectin and ICAM-1 on the surface of the endothelial cells after incubation with whole blood. There was no activation of the cells when the crystals were incubated in medium alone, or in human serum, despite substantial crystal-induced complement activation in serum. Complement inhibitors at the C3 and C5 levels reduced the whole blood induced endothelial cell activation by up to 89% (p<0.05) and abolished TNF release (p<0.01). Finally, the TNF inhibitor infliximab reduced endothelial activation to background levels (p<0.05). In conclusion, these data demonstrate that endothelial activation by cholesterol crystals is mediated by complement-dependent TNF release, and suggests that complement-inhibition might have a role in alleviating atherosclerosis-induced inflammation.

Cytoprotective signaling and gene expression in endothelial cells and macrophages-lessons for atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the medium and large arteries driven in large part by the accumulation of oxidized low-density lipoproteins and other debris at sites rendered susceptible because of the geometry of the arterial tree. As lesions develop, they acquire a pathologic microcirculation that perpetuates lesion progression, both by providing a means for further monocyte and T-lymphocyte recruitment into the arterial wall and by the physical and chemical stresses caused by micro-hemorrhage. This review summarizes work performed in our department investigating the roles of signaling pathways, alone and in combination, that lead to specific programs of gene expression in the atherosclerotic environment. Focusing particularly on cytoprotective responses that might be enhanced therapeutically, the work has encompassed the anti-inflammatory effects of arterial laminar shear stress, mechanisms of induction of membrane inhibitors that prevent complement-mediated injury, homeostatic macrophage responses to hemorrhage, and the transcriptional mechanisms that control the stability, survival, and quiescence of endothelial monolayers. Lastly, while the field has been dominated by investigation into the mechanisms of DNA transcription, we consider the importance of parallel post-transcriptional regulatory mechanisms for fine-tuning functional gene expression repertoires.

Cardioembolic and small vessel disease stroke show differences in associations between systemic C3 levels and outcome

Background

Activation of the complement system has been proposed to play a role in the pathophysiology of stroke. As the specific involvement of the complement proteins may be influenced by stroke etiology, we compared plasma C3 and C3a levels in patients with cardioembolic (CE) and small vessel disease (SVD) subtypes of ischemic stroke and control subjects and evaluated their association to outcome at three months and two years.

Methodology/Principal Findings

Plasma C3 and C3a levels in 79 CE and 79 SVD stroke patients, sampled within 10 days and at three months after stroke, and age- and sex-matched control subjects from The Sahlgrenska Academy Study on Ischemic Stroke were measured by ELISA. Functional outcome was assesed with modified Rankin Scale. In the CE group, plasma C3 levels were elevated only in the acute phase, whereas C3a was elevated at both time points. The follow-up phase plasma C3 levels in the upper third were associated with an increased risk of unfavorable outcome at three months (OR 7.12, CI 1.72–29.46, P = 0.007) as well as after two years (OR 8.25, CI 1.61–42.28, P = 0.011) after stroke. These associations withstand adjustment for age and sex. Conversely, three-month follow-up plasma C3a/C3 level ratios in the middle third were associated with favorable outcome after two years both in the univariate analysis (OR 0.19, CI 0.05–0.82, P = 0.026) and after adjustment for age and sex (OR 0.19, CI 0.04–0.88, P = 0.033). In the SVD group, plasma C3 and C3a levels were elevated at both time points but showed no significant associations with outcome.

Conclusions

Plasma C3 and C3a levels are elevated after CE and SVD stroke but show associations with outcome only in CE stroke.

High serum C1q-adiponectin/total adiponectin ratio correlates with coronary artery disease in Japanese type 2 diabetics

OBJECTIVE

Adiponectin, an adipocyte-derived protein, has potential antiatherogenic properties. Low levels of serum total-adiponectin (Total-APN) correlate with diabetes and coronary artery disease (CAD). Adiponectin and C1q form a protein complex in blood, and serum C1q-binding adiponectin (C1q-APN) can be measured. We investigated the correlation between C1q-APN and CAD in patients with type 2 diabetes mellitus (T2DM).

METHODS

The study subjects were 107 outpatients with T2DM who underwent evaluation for CAD. Blood C1q, Total-APN, high-molecular weight-adiponectin (HMW-APN) and C1q-APN were measured by enzyme-linked immunosorbent assays.

RESULTS

Serum levels of C1q-APN/Total-APN ratio were higher in patients diagnosed with CAD (10.47±0.59, mean±SEM, n=54) than those without CAD (8.88±0.60, n=53, p=0.0482). Age- and sex-adjusted logistic regression analysis identified serum C1q-APN/Total-APN ratio and hypertension as significant and independent determinants of CAD. A high serum C1q-APN/Total-APN ratio was associated with 3.965-fold increase in CAD prevalence.

CONCLUSIONS

High serum C1q-APN/Total-APN ratio correlates with CAD in T2DM.

Correlation between serum C1q-adiponectin/total adiponectin ratio and polyvascular lesions detected by vascular ultrasonography in Japanese type 2 diabetics

OBJECTIVE

Atherosclerosis is a disease of blood vessels. Adiponectin is a biomarker of atherosclerosis. Adiponectin and C1q form a protein complex in human blood, and serum C1q-binding adiponectin (C1q-APN) can be measured. We investigated the relationship between various serum adiponectin parameters and polyvascular atherosclerosis score assessed by vascular ultrasonography, in subjects with type 2 diabetes mellitus (T2DM).

METHODS

The study subjects were 108 outpatients with T2DM who underwent evaluation for atherosclerosis by vascular ultrasonography. Polyvascular atherosclerosis score represented the sum of atherosclerotic abnormalities in the aorta, carotid, renal and common iliac arteries. Blood C1q, total-adiponectin (Total-APN), high molecular weight-adiponectin (HMW-APN) and C1q-APN were measured by enzyme-linked immunosorbent assays. The estimated visceral fat area (eVFA) was measured by bioelectrical impedance.

RESULTS

Polyvascular atherosclerosis score correlated only with the C1q-APN/Total-APN ratio (p=0.018 for trend). There were no significant relationships between various adiponectin parameters and carotid maximum intima-media thickness and ankle-brachial index. Age-, sex-, eVFA-adjusted multiple logistic regression analysis that included the above variables identified serum C1q-APN/Total-APN ratio as the only significant and independent determinant of polyvascular atherosclerosis score.

CONCLUSIONS

Serum C1q-APN/Total-APN ratio correlates with atherosclerosis detected by polyvascular vascular ultrasonography, independent of gender and visceral adiposity, in T2DM.

Genetic-genomic replication to identify candidate mouse atherosclerosis modifier genes

Objective

Genetics plays a large role in atherosclerosis susceptibility in humans and mice. We attempted to confirm previously determined mouse atherosclerosis‐associated loci and use bioinformatics and transcriptomics to create a catalog of candidate atherosclerosis modifier genes at these loci.

Methods and Results

A strain intercross was performed between AKR and DBA/2 mice on the apoE^−/− background generating 166 F₂ progeny. Using the phenotype log10 of the aortic root lesion area, we identified 3 suggestive atherosclerosis quantitative trait loci (Ath QTLs). When combined with our prior strain intercross, we confirmed 3 significant Ath QTLs on chromosomes 2, 15, and 17, with combined logarithm of odds scores of 5.9, 5.3, and 5.6, respectively, which each met the genome‐wide 5% false discovery rate threshold. We identified all of the protein coding differences between these 2 mouse strains within the Ath QTL intervals. Microarray gene expression profiling was performed on macrophages and endothelial cells from this intercross to identify expression QTLs (eQTLs), the loci that are associated with variation in the expression levels of specific transcripts. Cross tissue eQTLs and macrophage eQTLs that replicated from a prior strain intercross were identified. These bioinformatic and eQTL analyses produced a comprehensive list of candidate genes that may be responsible for the Ath QTLs.

Conclusions

Replication studies for clinical traits as well as gene expression traits are worthwhile in identifying true versus false genetic associations. We have replicated 3 loci on mouse chromosomes 2, 15, and 17 that are associated with atherosclerosis. We have also identified protein coding differences and multiple replicated eQTLs, which may be useful in the identification of atherosclerosis modifier genes.

Distinct roles for complement in glomerulonephritis and atherosclerosis revealed in mice with a combination of lupus and hyperlipidemia

OBJECTIVE

Although the accelerating effect of systemic lupus erythematosus (SLE) on atherosclerosis is well established, the underlying mechanisms are unknown. The aim of this study was to explore the hypothesis that lupus autoimmunity modulates the effect of hypercholesterolemia in driving arterial pathologic development.

METHODS

Low-density lipoprotein receptor-deficient (Ldlr(-/-) ) mice were crossed with B6.129-Sle16 (Sle16)-congenic autoimmune mice to obtain Sle16. Ldlr(-/-) mice, which were compared with Ldlr(-/-) and Sle16 control mice. All mice were fed either a low-fat or high-fat diet. Groups of mice were compared, by strain and by diet group, for features of accelerated atherosclerosis and autoimmunity.

RESULTS

Presence of the Sle16 locus significantly increased the extent of atherosclerosis in Ldlr(-/-) mice. Circulating C3 levels were significantly reduced in Sle16.Ldlr(-/-) mice compared to Ldlr(-/-) control mice and this was paralleled by a marked reduction in arterial lesion C3 deposition despite similar levels of IgG deposition between the groups. Increased numbers of apoptotic cells in plaques were observed in the high-fat-fed Sle16.Ldlr(-/-) mice, consistent with the observed defective clearance of cellular debris. After receiving the high-fat diet, Sle16.Ldlr(-/-) mice developed glomerulonephritis and displayed enhanced glomerular C3 deposition.

CONCLUSION

These results indicate that accelerated atherosclerosis and renal inflammation in SLE are closely linked via immune complex formation and systemic complement depletion. However, whereas hyperlipidemia will enhance renal immune complex-mediated complement activation and the development of nephritis, accelerated atherosclerosis is, instead, related to complement depletion and a reduction in the uptake of apoptotic/necrotic debris. These results suggest that aggressive treatment of hyperlipidemia in patients with SLE may reduce the occurrence of lupus nephritis, as well as diminish the risk of accelerated atherosclerosis.

Model IgG monoclonal autoantibody-anti-idiotype pair for dissecting the humoral immune response to oxidized low density lipoprotein

Increasing evidence implicates IgG autoantibodies against oxidized forms of low density lipoprotein (oxLDL) in the pathophysiology of atherosclerotic arterial disease. However, insufficient knowledge of their structure and function is a key gap. Using an elderly LDL receptor-deficient atherosclerotic mouse, we isolated a novel IgG3k against oxLDL (designated MAb LO1). LO1 reacts with copper-oxidized LDL, but minimally with native LDL. Further analysis showed that MAb LO1 also reacts in vitro with malondialdehyde-conjugated LDL (MDA-LDL), a known key epitope in copper-oxidized LDL preparations. By screening a phage library expressing single chain variable region antibodies (scFv), we selected an anti-idiotype scFv (designated H3) that neutralizes MAb LO1 binding to MDA-LDL. Amino acid substitutions between H3 and an irrelevant control scFv C12 showed that residues in the H3 CDRH2, CDRH3, and CDRL2 are all critical for MAb LO1 binding, consistent with a conformational epitope on H3 involving both heavy and light chains. Comparison of amino acids in H3 CDRH2 and CDRL2 with apoB, the major LDL protein, showed homologous sequences, suggesting H3 has structural similarities to the MAb LO1 binding site on MDA-LDL. Immunocytochemical staining showed that MAb LO1 binds epitopes in mouse and human atherosclerotic lesions. The MAb LO1-H3 combination therefore provides a very promising model for analyzing the structure and function of an individual IgG autoantibody in relation to atherosclerosis.

Immunization With a Combination of 2 Peptides Derived From the C5a Receptor Significantly Reduces Early Atherosclerotic Lesion in Ldlr tm1Her Apob tm2Sgy J Mice

Objective—

The goal of this study was to assess whether immunization of Ldlr tm1Her Apob tm2Sgy J mice with 2 peptides located at the N-terminus of the C5a receptor (C5aR), either alone or in combination, is effective in reducing atherosclerotic lesions.

Methods and Results—

Five- to 6-week-old female Ldlr tm1Her Apob tm2Sgy J mice were immunized using a repetitive immunization multiple sites strategy with keyhole limpet hemocyanin-conjugated peptides derived from the C5aR, either alone (designated as C5aR-P1 [aa 1–21] and C5aR-P2 [aa 19–31]) or in combination (designated as C5aR-P1+C5aR-P2). Mice were fed a high-fat diet for 10 weeks. Lesions were evaluated histologically; local and systemic immune responses were analyzed by immunohistochemistry of aorta samples and cytokine measurements in plasma samples and splenocyte supernatants. Immunization of Ldlr tm1Her Apob tm2Sgy J mice with these peptides elicited high concentrations of antibodies against each peptide. Immunization with the single peptide inhibited plaque development. Combined inoculation with C5aR-P1+C5aR-P2 had an additive effect on reducing the lesion in the aorta sinus and descending aortas when compared with controls. This effect correlated with cellular infiltration and cytokine/chemokine secretion in the serum or in stimulated spleen cells as well as specific cellular immune responses when compared with controls.

Conclusion—

Immunization of mice with C5aR-P1 and C5aR-P2, either alone or in combination, was effective in reducing early atherosclerotic lesion development. The combined peptide is more potential than either epitope alone to reduce atherosclerotic lesion formation through the induction of a specific Treg cell response as well as blockage of monocyte differentiation into macrophages.

Influence of hypertension, obesity and nicotine abuse on quantitative and qualitative changes in acute-phase proteins in patients with essential hypertension

Background

Hypertension is a powerful risk factor for cardiovascular disease and frequently occurs in conjunction with obesity. Accumulative evidence suggests a link between inflammation and hypertension. The aim of study was to evaluate whether blood pressure, obesity and smoking may influence acute-phase response.

Material/Methods

Ninety-two patients with essential hypertension and 75 healthy volunteers as a control group were studied. In all subjects assessment of hsCRP, α1-acid glycoprotein (AGP), α1-antichymotrypsin, transferrin, α1-antitrypsin, and C3 and C4 complement were performed. Evaluation of glycosylation profile and reactivity coefficient (RC) for AGP was done by means of affinity immunoelectrophoresis with concanavalin A as a ligand.

Results

When compared to the controls, hypertensive subjects presented significantly higher hsCRP concentrations and lower transferrin level. Hypertensive patients had elevated AGP-AC. The intensification of the inflammatory reaction was greater in the subgroup of hypertensive patients smoking cigarettes. In obese hypertensives, elevated serum C3 complement level was found.

Conclusions

We conclude that arterial hypertension may evoke the acute-phase response in humans. Markers of acute-phase response are particularly strongly expressed in smokers. Serum C 3 complement, but not other APPs, is elevated in hypertension coexisting with obesity.

Obesity and clustering of cardiovascular disease risk factors are associated with elevated plasma complement C3 in children and adolescents

OBJECTIVES

To investigate the relationship among obesity, cardiovascular disease risk factors (CVDRFs), and plasma complement C3 concentration in children and adolescents.

METHODS

In a nationwide survey conducted between 1992 and 2000, all school children aged 6-18 yr with abnormal results in repeated urine samples, including hematuria, proteinuria, and glucosuria (n = 97 312; 36 557 boys and 60 755 girls), were investigated for their body mass index (BMI), blood pressure, fasting plasma glucose, total cholesterol, and plasma complement C3 concentrations.

RESULTS

Children in the higher percentile groups for BMI or having more CVDRFs, namely, hypertension, diabetes, and hypercholesterolemia, had higher plasma C3 concentrations independently (p for both trends <0.05, adjusted for age and gender). The odds ratios (ORs) for having one, two, or three CVDRFs in obese children were 4.74 [95% confidence interval (CI) = 4.47-5.03], 19.8 (95% CI = 17.8-22.0), and 139 (95% CI = 96.6-200), respectively, adjusted for age, gender, and family history of diabetes, which were substantially reduced after adjustment for plasma C3 concentrations. The ORs for children with plasma C3 concentrations in the highest quartile to have one, two, or three CVDRFs were 2.32 (95% CI = 2.21-2.44), 5.68 (95% CI = 4.83-6.67), and 58.6 (95% CI = 19.7-174), respectively, adjusted for age, gender, family history of diabetes, and BMI.

CONCLUSION

Obesity is associated with clustering of CVDRFs in children and adolescents. Obesity and clustering of CVDRFs are associated with elevated plasma complement C3. Children and adolescents with higher plasma C3 concentrations have higher risk of clustering of CVDRFs independent of obesity.

Complement profile and activation mechanisms by different LDL apheresis systems

Extracorporeal removal of low-density lipoprotein (LDL) cholesterol by means of selective LDL apheresis is indicated in otherwise uncontrolled familial hypercholesterolemia. During blood-biomaterial interaction other constituents than the LDL particles are affected, including the complement system. We set up an ex vivo model in which human whole blood was passed through an LDL apheresis system with one of three different apheresis columns: whole blood adsorption, plasma adsorption and plasma filtration. The concentrations of complement activation products revealed distinctly different patterns of activation and adsorption by the different systems. Evaluated as the final common terminal complement complex (TCC) the whole blood system was inert, in contrast to the plasma systems, which generated substantial and equal amounts of TCC. Initial classical pathway activation was revealed equally for both plasma systems as increases in the C1rs-C1inh complex and C4d. Alternative pathway activation (Bb) was most pronounced for the plasma adsorption system. Although the anaphylatoxins (C3a and C5a) were equally generated by the two plasma separation systems, they were efficiently adsorbed to the plasma adsorption column before the "outlet", whereas they were left free in the plasma in the filtration system. Consequently, during blood-biomaterial interaction in LDL apheresis the complement system is modulated in different manners depending on the device composition.

Effect of weight loss on C3 and C4 components of complement in obese patients

BACKGROUND

Circulating C3 levels are elevated in obese patients, but how this factor is affected after weight loss through diet is a question that is yet unanswered. Therefore, the aim of this study was to evaluate the effects of weight loss on lipid and hydrocarbonated metabolism parameters and on the levels of C3 and C4 components of complement in obese patients.

DESIGN

This is a longitudinal intervention study based on a 6-week very low-calorie diet (VLCD), a liquid formula of 603 kcal/day. A total of 131 middle-aged patients were distributed among grades II, III and IV of obesity. Anthropometric parameters, total cholesterol, triglycerides, high-density lipoprotein cholesterol, LDLc, apolipoproteins A-I and B-100, glucose, insulin, HOMA-IR and C3 and C4 levels were evaluated at baseline and after 6 weeks of intervention.

RESULTS

After VLCD, the moderate weight loss was accompanied by a significant reduction in C3 levels in grade III and grade IV patients (10.2% and 15.4%, respectively; P < 0.001). C4 levels were not altered. Adherence to the diet improved anthropometric parameters and was accompanied by a significant decrease in all lipid profile parameters (P < 0.001). In addition, weight loss was associated with an improvement in hydrocarbonated metabolism as shown by the decrease in glucose levels and HOMA-IR (P < 0.01).

CONCLUSIONS

Our findings show that in severely obese patients following a VLCD for 6 weeks produces reductions in factor C3, a biomarker of cardiovascular disease, and a significant improvement in some features of metabolic syndrome. In this way, the abovementioned diet may represent an effective strategy for treating obesity and related cardiovascular risk factors.

Genes involved in systemic and arterial bed dependent atherosclerosis--Tampere Vascular study

Background

Atherosclerosis is a complex disease with hundreds of genes influencing its progression. In addition, the phenotype of the disease varies significantly depending on the arterial bed.

Methodology/Principal Findings

We characterized the genes generally involved in human advanced atherosclerotic (AHA type V–VI) plaques in carotid and femoral arteries as well as aortas from 24 subjects of Tampere Vascular study and compared the results to non-atherosclerotic internal thoracic arteries (n=6) using genome-wide expression array and QRT-PCR. In addition we determined genes that were typical for each arterial plaque studied. To gain a comprehensive insight into the pathologic processes in the plaques we also analyzed pathways and gene sets dysregulated in this disease using gene set enrichment analysis (GSEA). According to the selection criteria used (>3.0 fold change and p-value <0.05), 235 genes were up-regulated and 68 genes down-regulated in the carotid plaques, 242 genes up-regulated and 116 down-regulated in the femoral plaques and 256 genes up-regulated and 49 genes down-regulated in the aortic plaques. Nine genes were found to be specifically induced predominantly in aortic plaques, e.g., lactoferrin, and three genes in femoral plaques, e.g., chondroadherin, whereas no gene was found to be specific for carotid plaques. In pathway analysis, a total of 28 pathways or gene sets were found to be significantly dysregulated in atherosclerotic plaques (false discovery rate [FDR] <0.25).

Conclusions

This study describes comprehensively the gene expression changes that generally prevail in human atherosclerotic plaques. In addition, site specific genes induced only in femoral or aortic plaques were found, reflecting that atherosclerotic process has unique features in different vascular beds.

CD55 deficiency protects against atherosclerosis in ApoE-deficient mice via C3a modulation of lipid metabolism

Atherosclerosis, the leading cause of death in the Western world, is driven by chronic inflammation within the artery wall. Elements of the complement cascade are implicated in the pathogenesis, because complement proteins and their activation products are found in the atherosclerotic plaque. We examined the role of CD55, a membrane inhibitor of the complement component 3 (C3) convertase, which converts C3 into C3a and C3b, in atherosclerosis. CD55-deficient (CD55^−/−) mice were crossed onto the atherosclerosis-prone apolipoprotein E (apoE)-deficient (apoE^−/−) background. High fat–fed male apoE^−/−/CD55^−/− mice were strongly protected from developing atherosclerosis compared with apoE^−/− controls. Lipid profiling showed significantly lower levels of triglycerides, nonesterified fatty acids, and cholesterol in apoE^−/−/CD55^−/− mice than that in controls after high-fat feeding, whereas body fat in apoE^−/−/CD55^−/− mice content was increased. Plasma levels of C3 fell, whereas concentrations of C3adesArg (alias acylation stimulating protein; ASP), produced by serum carboxypeptidase N–mediated desargination of C3a, increased in nonfasted high fat–fed apoE^−/−/CD55^−/− mice, indicating complement activation. Thus, complement dysregulation in the absence of CD55 provoked increased C3adesArg production that, in turn, caused altered lipid handling, resulting in atheroprotection and increased adiposity. Interventions that target complement activation in adipose tissue should be explored as lipid-decreasing strategies.

Proteomics of Lipoprotein(a) identifies a protein complement associated with response to wounding

Lipoprotein(a) [Lp(a)] is a major independent risk factor for cardiovascular disease. Twenty percent of the general population exhibit levels above the risk threshold highlighting the importance for clinical and basic research. Comprehensive proteomics of human Lp(a) will provide significant insights into Lp(a) physiology and pathogenicity. Using liquid chromatography-coupled mass spectrometry, we established a high confidence Lp(a) proteome of 35 proteins from highly purified particles. Protein interaction network analysis and functional clustering revealed proteins assigned to the two major biological processes of lipid metabolism and response to wounding. The latter includes the processes of coagulation, complement activation and inflammatory response. Furthermore, absolute protein quantification of apoB-100, apo(a), apoA1, complement C3 and PON1 gave insights into the compositional stoichiometry of associated proteins per particle. Our proteomics study has identified Lp(a)-associated proteins that support a suggested role of Lp(a) in response to wounding which points to mechanisms of Lp(a) pathogenicity at sites of vascular injury and atherosclerotic lesions. This study has identified a high confidence Lp(a) proteome and provides an important basis for further comparative and quantitative analyses of Lp(a) isolated from greater numbers of plasma samples to investigate the significance of associated proteins and their dynamics for Lp(a) pathogenicity.

Complement C5a inhibition reduces atherosclerosis in ApoE-/- mice

The complement C5a receptor, CD88, is present on many of the cells found within human atherosclerotic plaques, but little is known about the role of C5a in atherogenesis. Using real-time PCR, we determined that ApoE(-/-) mice fed a normal diet express more aortic CD88 mRNA compared with controls, and this increase coincides with atherosclerotic lesion development (P<0.001 for 3- vs. 25-wk-old animals). Conversely, mRNA expression of the alternative C5a receptor, C5L2, in aortas of ApoE(-/-) mice, was lower than controls at all time points. Using immunohistochemistry, we confirmed the presence of CD88 on macrophages, smooth muscle cells, and activated endothelial cells in plaques from brachiocephalic arteries. Treatment of ApoE(-/-) mice with a CD88 antagonist (PMX53; 3 mg/kg s.c. 3 ×/wk plus 1 mg/kg/d p.o.) for 25 wk reduced lesion size and lipid content in the plaque by ∼ 40% (P<0.05). Our study provides evidence for a proatherogenic role for C5a and identifies the CD88 antagonist PMX53 as a potential antiatherosclerotic drug.