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

Colchicine: an affordable anti-inflammatory agent for atherosclerosis

PURPOSE OF REVIEW

Inflammation has been shown to be central to the development and progression of atherosclerosis. Despite detailed understanding of its central role and the cellular dynamics, which contribute to atherosclerotic inflammation, there has been slow progress in finding suitable agents to treat it. The recent CANTOS trial showed that the interleukin-1β inhibitor canakinumab can improve outcomes after acute coronary syndromes. Being a monoclonal antibody, it is expensive and inconvenient to administer for long-term treatment. This review summarizes recent work in finding effective, affordable alternatives to canakinumab.

RECENT FINDINGS

Statin drugs have anti-inflammatory properties but separating their LDL lowering effect from their anti-inflammatory effect has been difficult. Drugs acting on targets outside of the interleukin-1β (IL-1β) pathway have been tested without finding a suitable candidate. Following the proof of principle provided by the success of canakinumab, other candidates targeting the IL-1β pathway are undergoing detailed evaluation. The most likely candidates are low-dose methotrexate and low-dose colchicine. The potential mechanisms and ongoing clinical trials are described.

SUMMARY

Targeting the IL-1β pathway has already been successful with canakinumab but its expense and inconvenience of administration may limit its widespread uptake for controlling inflammation in atherosclerosis. Low-dose methotrexate and low-dose colchicine are affordable and more accessible alternatives, currently undergoing detailed evaluation for safety and efficacy in large randomized controlled trials.

Genetic Regulatory Mechanisms of Smooth Muscle Cells Map to Coronary Artery Disease Risk Loci

Coronary artery disease (CAD) is the leading cause of death globally. Genome-wide association studies (GWASs) have identified more than 95 independent loci that influence CAD risk, most of which reside in non-coding regions of the genome. To interpret these loci, we generated transcriptome and whole-genome datasets using human coronary artery smooth muscle cells (HCASMCs) from 52 unrelated donors, as well as epigenomic datasets using ATAC-seq on a subset of 8 donors. Through systematic comparison with publicly available datasets from GTEx and ENCODE projects, we identified transcriptomic, epigenetic, and genetic regulatory mechanisms specific to HCASMCs. We assessed the relevance of HCASMCs to CAD risk using transcriptomic and epigenomic level analyses. By jointly modeling eQTL and GWAS datasets, we identified five genes (SIPA1, TCF21, SMAD3, FES, and PDGFRA) that may modulate CAD risk through HCASMCs, all of which have relevant functional roles in vascular remodeling. Comparison with GTEx data suggests that SIPA1 and PDGFRA influence CAD risk predominantly through HCASMCs, while other annotated genes may have multiple cell and tissue targets. Together, these results provide tissue-specific and mechanistic insights into the regulation of a critical vascular cell type associated with CAD in human populations.

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.

Influence of Inflammation and Atherosclerosis in Atrial Fibrillation

BACKGROUND

Inflammation markers have been associated with cardiovascular diseases including atrial fibrillation. This arrhythmia is the most frequent, with an incidence of 38/1000 person-years.

PURPOSE OF REVIEW

The aims of this study are to discuss the association between inflammation, atherosclerosis and atrial fibrillation and its clinical implications. Atherosclerosis is a chronic inflammatory disease and inflammation is a triggering factor of atherosclerotic plaque rupture. In addition to coronary artery disease, clinical conditions identified as risk factors for atrial fibrillation (AF) are also associated with the inflammatory state such as obesity, diabetes mellitus, hypertension, heart failure, metabolic syndrome and sedentary lifestyle. Biomarkers of inflammation, oxidative stress, coagulation, and myocardial necrosis have been identified in patients with atrial fibrillation and these traditional risk factors. Some markers of inflammation were identified as predictors of recurrence of this arrhythmia, subsequent myocardial infarction, stroke by embolism, and death. Thus, approaches to manipulate the inflammatory pathways may be therapeutic interventions, benefiting patients with AF and increased inflammatory markers.

Toll-Like Receptors 2 and 4 Predict New-Onset Atrial Fibrillation in Acute Myocardial Infarction Patients

Myocardial infarction (MI) can cause new-onset atrial fibrillation (AF) due to cardiac remodeling. As a recent study has shown, inflammatory factors are closely tied to cell death and survival in myocardial ischemia injury. Toll-like receptors (TLRs) have been shown to participate in the process of myocardial infarction as innate immune factors.The subjects were divided into 3 groups: healthy controls (n = 82), MI patients (n = 84), and AFMI (new-onset atrial fibrillation after myocardial infarction) patients (n = 85). Peripheral blood mononuclear cell (PBMC) TLR mRNA expression was detected by rt-PCR. Western blot was used to analyze PBMC TLRs and their downstream signal protein expression. PBMCs were presented as TLR2 expression or TLR4 expression using flow cytometry.From mRNA to protein detection, PBMC TLR2 and TLR4 were significantly higher in the AFMI group than in the control group and MI group. A similar tendency was also observed in the expression of downstream signaling proteins. When further analyzed with TLR2 and TLR4 antibodies by flow cytometry, PBMC levels also appeared to be higher in AFMI patients than those in MI patients and the healthy control group.In our study, PBMC TLRs and their downstream signaling proteins were significantly higher in the acute myocardial infarction patients with new-onset atrial fibrillation compared with healthy people and acute myocardial infarction patients without new-onset atrial fibrillation. They have the potential to be novel biomarkers for new-onset atrial fibrillation after acute myocardial infarction.

Post-transplant hypocomplementemia: A novel marker of cardiovascular risk in kidney transplant recipients?

BACKGROUND AND AIMS

Cardiovascular disease (CVD) is a leading cause of mortality after kidney transplantation (KT). The potential role of the complement system in the pathogenesis of post-transplant CVD remains unexplored.

METHODS

Serum complement (C3 and C4) levels were measured at baseline and post-transplant months 1 and 6 in 447 kT recipients. The study outcome was post-transplant atherothrombotic event (PAE), a composite of acute coronary syndrome, critical peripheral arterial disease, stroke and/or transient ischemic attack.

RESULTS

After a median follow-up of 4.2 years, 48 PAEs occurred in 43 patients (cumulative incidence: 9.6%; incidence rate: 2.6 events per 100 transplant-years). No differences were found in C3 and C4 levels at baseline or month 1 between patients with or without PAE. However, C3 levels at month 6 were significantly lower in patients developing PAE beyond that point (i.e., late PAE) (96.9 ± 22.3 vs. 109.6 ± 24.0 mg/dL; p = 0.013). The presence of C3 hypocomplementemia at month 6 was associated with a lower PAE-free survival (p = 0.002). After adjusting for conventional CVD risk factors and acute graft rejection, C3 hypocomplementemia at month 6 remained as an independent risk factor for late PAE in all the exploratory models (minimum hazard ratio: 3.24; p = 0.011). With respect to a model exclusively based on clinical variables, the inclusion of C3 levels at month 6 improved predictive capacity (areas under ROC curves: 0.788 and 0.812, respectively).

CONCLUSIONS

Post-transplant monitoring of serum C3 levels might be useful to identify KT recipients at increased risk of CVD.

Voluntary exercise slows breast tumor establishment and reduces tumor hypoxia in ApoE-/- mice

Exercise reduces the risk of breast cancer development and improves survival in breast cancer patients. However, the underlying mechanisms of this protective effect remain to be fully elucidated, and it is unclear whether exercise can attenuate the protumor effects of obesity and related hyperlipidemia on breast cancer growth and development. We hypothesized that exercise attenuates the negative effect of hyperlipidemia through normalization of the tumor microenvironment and improved T cell infiltrate. Hyperlipidemic ApoE^-/- mice with orthotopic EO771 breast tumors were randomly assigned to one of two voluntary running groups or sedentary controls, and muscular cytochrome c oxidase subunit IV (COX-IV) expression was used as a biomarker for the level of exercise. Tumors from mice with high muscular COX-IV expression took significantly longer to reach 100 mm³ ( P = 0.008), but showed no difference in growth rate once the tumor was established. Wheel running appeared to reduce internal metastases, but did not affect T cell infiltrate or the proportion of regulatory and cytotoxic T cells within the tumor. Serum levels of monocyte chemoattractant protein-1 (MCP-1) were significantly increased by tumor burden ( P = 0.02) and correlated with spleen weight ( P < 0.0001, R = 0.65). Furthermore, tumor hypoxia was significantly decreased in mice with high muscular COX-IV expression ( P = 0.01). Taken together, these results indicate that wheel running can slow the establishment of primary and secondary EO771 breast tumors and induce beneficial changes in the breast tumor microenvironment in ApoE^-/- mice. NEW & NOTEWORTHY In this first study to investigate the effect of exercise on tumor behavior in a hyperlipidemic model, we hypothesized that wheel running would counteract the protumorigenic environment generated by hyperlipidemia. Wheel running slowed establishment of primary and secondary tumors and reduced tumor hypoxia but did not affect exponential tumor growth in ApoE^-/- mice. Overall, voluntary wheel running induced favorable microenvironmental changes in breast tumors.

Maternal Gestational Diabetes Mellitus increases placental and foetal lipoprotein-associated Phospholipase A2 which might exert protective functions against oxidative stress

Increased Lipoprotein associated phospholipase A2 (LpPLA2) has been associated with inflammatory pathologies, including Type 2 Diabetes. Studies on LpPLA2 and Gestational Diabetes Mellitus (GDM) are rare, and have focused mostly on maternal outcome. In the present study, we investigated whether LpPLA2 activity on foetal lipoproteins is altered by maternal GDM and/or obesity (a major risk factor for GDM), thereby contributing to changes in lipoprotein functionality. We identified HDL as the major carrier of LpPLA2 activity in the foetus, which is in contrast to adults. We observed marked expression of LpPLA2 in placental macrophages (Hofbauer cells; HBCs) and found that LpPLA2 activity in these cells was increased by insulin, leptin, and pro-inflammatory cytokines. These regulators were also increased in plasma of children born from GDM pregnancies. Our results suggest that insulin, leptin, and pro-inflammatory cytokines are positive regulators of LpPLA2 activity in the foeto-placental unit. Of particular interest, functional assays using a specific LpPLA2 inhibitor suggest that high-density lipoprotein (HDL)-associated LpPLA2 exerts anti-oxidative, athero-protective functions on placental endothelium and foetus. Our results therefore raise the possibility that foetal HDL-associated LpPLA2 might act as an anti-inflammatory enzyme improving vascular barrier function.

Shear stress-mediated changes in the expression of complement regulatory protein CD59 on human endothelial progenitor cells by ECM-integrinαVβ3-F-actin pathway in vitro

Membrane regulatory proteins, such as CD46, CD55, and CD59, prevent excess complement activation and to protect cells from damage. Previous investigations confirmed that shear stress in the physiological range was more favorable for endothelial progenitor cells (EPCs) to repair injured vascular endothelial cells and operates mainly in atheroprotective actions. However, detailed events that contribute to shear stress-induced protection in EPCs, particularly the mechanisms of signal transduction, remain poorly understood. In this study, we observed shear stress-mediated changes in the expression of complement regulatory proteins CD46, CD55, and CD59 on human EPCs and focused on the mechanical transmission mechanism in transformed cells in response to the ECM-F-actin pathway in vitro. Shear stress was observed to promote the expression of complement regulatory protein CD59, but not CD46 or CD55, on EPCs. In addition, the shear stress-induced CD59 expression was confirmed to be associated with the ECM components and was alleviated in EPCs pretreated with GRGDSP, which inhibits ECM components-integrin interaction. Furthermore, shear stress also promotes the rearrangement and polymerization of F-actin. However, shear stress-induced CD59 expression was reduced when the F-actin stress fiber formation process was delayed by Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) or destroyed by cytochalasin D (Cyto D), while Jasplakinolide (JAS) reversed the expression of CD59 through promotion of F-actin polymerization and its stabilizing capacities. Our results indicates that shear stress is an important mediator in EPC expression of CD59 regulated by the ECM-F-actin pathway, which is a key factor in preventing membrane attack complex (MAC) -mediated cell autolysis.

Chronic Inflammation in Immune Aging: Role of Pattern Recognition Receptor Crosstalk with the Telomere Complex?

Age-related decline in immunity is characterized by stem cell exhaustion, telomere shortening, and disruption of cell-to-cell communication, leading to increased patient risk of disease. Recent data have demonstrated that chronic inflammation exerts a strong influence on immune aging and is closely correlated with telomere length in a range of major pathologies. The current review discusses the impact of inflammation on immune aging, the likely molecular mediators of this process, and the various disease states that have been linked with immunosenescence. Emerging findings implicate NF-κB, the major driver of inflammatory signaling, in several processes that regulate telomere maintenance and/or telomerase activity. While prolonged triggering of pattern recognition receptors is now known to promote immunosenescence, it remains unclear how this process is linked with the telomere complex or telomerase activity. Indeed, enzymatic control of telomere length has been studied for many decades, but alternative roles of telomerase and potential influences on inflammatory responses are only now beginning to emerge. Crosstalk between these pathways may prove to be a key molecular mechanism of immunosenescence. Understanding how components of immune aging interact and modify host protection against pathogens and tumors will be essential for the design of new vaccines and therapies for a wide range of clinical scenarios.

More than complementing Tolls: complement-Toll-like receptor synergy and crosstalk in innate immunity and inflammation

Complement and Toll-like receptors (TLRs) play key roles in the host immune response and are swiftly activated by infection or other types of immunological stress. This review focuses on the capacity of complement and TLRs to engage in signaling crosstalk, ostensibly to coordinate immune and inflammatory responses through synergistic or antagonistic (regulatory) interactions. However, overactivation or dysregulation of either system may lead-often synergistically-to exaggerated inflammation and host tissue injury. Intriguingly, moreover, certain pathogens can manipulate complement-TLR crosstalk pathways in ways that undermine host immunity and favor their persistence. In the setting of polymicrobial inflammatory disease, subversion of complement-TLR crosstalk by keystone pathogens can promote dysbiosis. Knowledge of the molecular mechanisms underlying complement-TLR crosstalk pathways can, therefore, be used productively for tailored therapeutic approaches, such as, to enhance host immunity, mitigate destructive inflammation, or counteract microbial subversion of the host response.

The Controversial C5a Receptor C5aR2: Its Role in Health and Disease

After the discovery of the C5a receptor C5aR1, C5aR2 is the second receptor found to bind C5a and its des-arginine form. As a heptahelical G protein-coupled receptor but devoid of the intracellular Gα signal, C5aR2 is special and confusing. Ramifications and controversies about C5aR2 are under debate since its identification, from putative ligands and cellular localization to intracellular signals and pathological roles in inflammation and immunity. The ruleless and even conflicting pro- or anti-inflammatory role of C5aR2 in animal models of diverse diseases makes one bewildered. This review summarizes reports on C5aR2, tries to clear up available evidence on these four controversial aspects, and delineates C5aR2 function(s). It also summarizes available toolboxes for C5aR2 study.

Toll-like receptor 7 deficiency protects apolipoprotein E-deficient mice from diet-induced atherosclerosis

Toll-like receptor 7 (TLR7) mediates autoantigen and viral RNA-induced cytokine production. Increased TLR7 expression in human atherosclerotic lesions suggests its involvement in atherogenesis. Here we demonstrated TLR7 expression in macrophages, smooth muscle cells (SMCs), and endothelial cells from mouse atherosclerotic lesions. To test a direct participation of TLR7 in atherosclerosis, we crossbred TLR7-deficient (Tlr7 ^-/-) mice with apolipoprotein E-deficient (Apoe ^-/-) mice and produced Apoe ^-/- Tlr7 ^-/- and Apoe ^-/- Tlr7 ^+/+ littermates, followed by feeding them an atherogenic diet to produce atherosclerosis. Compared to Apoe ^-/- Tlr7 ^+/+ mice, Apoe ^-/- Tlr7 ^-/- mice showed reduced aortic arch and sinus lesion areas. Reduced atherosclerosis in Apoe ^-/- Tlr7 ^-/- mice did not affect lesion macrophage-positive area and CD4⁺ T-cell number per lesion area, but reduced lesion expression of inflammatory markers major histocompatibility complex-class II and IL6, lesion matrix-degrading proteases cathepsin S and matrix metalloproteinase-9, and systemic serum amyloid A levels. TLR7 deficiency also reduced aortic arch SMC loss and lesion intima and media cell apoptosis. However, TLR7 deficiency did not affect aortic wall elastin fragmentation and collagen contents, or plasma lipoproteins. Therefore, TLR7 contributes to atherogenesis in Apoe ^-/- mice by regulating lesion and systemic inflammation. A TLR7 antagonist may mitigate atherosclerosis.

Novel protein biomarkers associated with coronary artery disease in statin-treated patients with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is the most common and serious monogenic disorder of lipid metabolism. The incidence of coronary artery disease (CAD) varies among both treated and untreated FH patients.

OBJECTIVE

The aim of the study was to utilize proteomics to identify novel protein biomarkers that differentiate genetically confirmed heterozygous patients with FH at high CAD risk from those at low CAD risk.

METHODS

Sixty genetically confirmed FH patients were recruited and stratified into (1) asymptomatic FH with low atherosclerotic burden (FH, n = 20); (2) asymptomatic FH with high atherosclerotic burden (FH + Ca, n = 20); and (3) FH with previously confirmed symptomatic CAD (FH + CAD, n = 20).

RESULTS

Six new potential proteins were identified; leucine-rich alpha-2-glycoprotein (LRG1), inter-alpha-trypsin inhibitor heavy chain H3, complement C4-B (C4B), complement C1q subcomponent subunit B (C1QB), monocyte differentiation antigen (CD14), and histidine-rich glycoprotein (HRG). There were significant associations between gender and C4B (Z = 2.31, P = .021), C1QB (Z = 2.49, P = .013), CD14 (Z = 2.17, P = .03), and HRG (Z = 2.14, P = .033). There were significant associations between smoking and LRG1 (χ²₂ = 6.59, P = .037), CB4 (χ²₂ = 7.85, P = .02), and HRG (χ²₂ = 6.11, P = .047). All the peptides were significantly associated with advanced CAD stages, independently of age and smoking. However, the absence of the proteins was the strongest marker. The most accurate association with CAD was HRG (area under the receiver operating characteristic curve = 0.922), whereas LRG1, C4B, and C1QB were also associated with CAD (area under the receiver operating characteristic curve >0.9). For either coronary atherosclerosis or CAD, LRG1, C4B, C1QB, and HRG were relatively well associated.

CONCLUSIONS

The present study has identified 6 novel protein biomarkers that are associated with more advanced stages of atherosclerotic disease and subsequent coronary events in patients with heterozygous FH.

Inhibition of epidermal growth factor receptor attenuates atherosclerosis via decreasing inflammation and oxidative stress

Atherosclerosis is a progressive disease leading to loss of vascular homeostasis and entails fibrosis, macrophage foam cell formation, and smooth muscle cell proliferation. Recent studies have reported that epidermal growth factor receptor (EGFR) is involved vascular pathophysiology and in the regulation of oxidative stress in macrophages. Although, oxidative stress and inflammation play a critical role in the development of atherosclerosis, the underlying mechanisms are complex and not completely understood. In the present study, we have elucidated the role of EGFR in high-fat diet-induced atherosclerosis in apolipoprotein E null mice. We show increased EGFR phosphorylation and activity in atherosclerotic lesion development. EGFR inhibition prevented oxidative stress, macrophage infiltration, induction of pro-inflammatory cytokines, and SMC proliferation within the lesions. We further show that EGFR is activated through toll-like receptor 4. Disruption of toll-like receptor 4 or the EGFR pathway led to reduced inflammatory activity and foam cell formation. These studies provide evidence that EGFR plays a key role on the pathogenesis of atherosclerosis, and suggests that EGFR may be a potential therapeutic target in the prevention of atherosclerosis development.

Dietary intake alters gene expression in colon tissue: possible underlying mechanism for the influence of diet on disease

Supplemental Digital Content is available in the text.

Background

Although the association between diet and disease is well documented, the biologic mechanisms involved have not been entirely elucidated. In this study, we evaluate how dietary intake influences gene expression to better understand the underlying mechanisms through which diet operates.

Methods

We used data from 144 individuals who had comprehensive dietary intake and gene expression data from RNAseq using normal colonic mucosa. Using the DESeq2 statistical package, we identified genes that showed statistically significant differences in expression between individuals in high-intake and low-intake categories for several dietary variables of interest adjusting for age and sex. We examined total calories, total fats, vegetable protein, animal protein, carbohydrates, trans-fatty acids, mutagen index, red meat, processed meat, whole grains, vegetables, fruits, fiber, folate, dairy products, calcium, and prudent and western dietary patterns.

Results

Using a false discovery rate of less than 0.1, meat-related foods were statistically associated with 68 dysregulated genes, calcium with three dysregulated genes, folate with four dysregulated genes, and nonmeat-related foods with 65 dysregulated genes. With a more stringent false discovery rate of less than 0.05, there were nine meat-related dysregulated genes and 23 nonmeat-related genes. Ingenuity pathway analysis identified three major networks among genes identified as dysregulated with respect to meat-related dietary variables and three networks among genes identified as dysregulated with respect to nonmeat-related variables. The top networks (Ingenuity Pathway Analysis network score >30) associated with meat-related genes were (i) cancer, organismal injury, and abnormalities, tumor morphology, and (ii) cellular function and maintenance, cellular movement, cell death, and survival. Among genes related to nonmeat consumption variables, the top networks were (i) hematological system development and function, nervous system development and function, tissue morphology and (ii) connective tissue disorders, organismal injury, and abnormalities.

Conclusion

Several dietary factors were associated with gene expression in our data. These findings provide insight into the possible mechanisms by which diet may influence disease processes.

Lectin Pathway of Complement Activation Is Associated with Vulnerability of Atherosclerotic Plaques

Inflammatory mechanisms may be involved in atherosclerotic plaque rupture. By using a novel histology-based method to quantify plaque instability here, we assess whether lectin pathway (LP) of complement activation, a major inflammation arm, could represent an index of plaque instability. Plaques from 42 consecutive patients undergoing carotid endarterectomy were stained with hematoxylin-eosin and the lipid core, cholesterol clefts, hemorrhagic content, thickness of tunica media, and intima, including or not infiltration of cellular debris and cholesterol, were determined. The presence of ficolin-1, -2, and -3 and mannose-binding lectin (MBL), LP initiators, was assessed in the plaques by immunofluorescence and in plasma by ELISA. LP activation was assessed in plasma by functional in vitro assays. Patients presenting low stenosis (≤75%) had higher hemorrhagic content than those with high stenosis (>75%), indicating increased erosion. Increased hemorrhagic content and tunica media thickness, as well as decreased lipid core and infiltrated content were associated with vulnerable plaques and therefore used to establish a plaque vulnerability score that allowed to classify patients according to plaque vulnerability. Ficolins and MBL were found both in plaques’ necrotic core and tunica media. Patients with vulnerable plaques showed decreased plasma levels and intraplaque deposition of ficolin-2. Symptomatic patients experiencing a transient ischemic attack had lower plasma levels of ficolin-1. We show that the LP initiators are present within the plaques and their circulating levels change in atherosclerotic patients. In particular, we show that decreased ficolin-2 levels are associated with rupture-prone vulnerable plaques, indicating its potential use as marker for cardiovascular risk assessment in atherosclerotic patients.

Pentraxin 3, ficolin-2 and lectin pathway associated serine protease MASP-3 as early predictors of myocardial infarction - the HUNT2 study

The lectin complement pathway is suggested to play a role in atherogenesis. Pentraxin-3 (PTX3), ficolin-1, ficolin-2, ficolin-3, MBL/ficolin/collectin-associated serine protease-3 (MASP-3) and MBL/ficolin/collectin-associated protein-1 (MAP-1) are molecules related to activation of the lectin complement pathway. We hypothesized that serum levels of these molecules may be associated with the incidence of myocardial infarction (MI). In a Norwegian population-based cohort (HUNT2) where young to middle-aged relatively healthy Caucasians were followed up for a first-time MI from 1995-1997 through 2008, the 370 youngest MI patients were matched by age (range 29-62 years) and gender to 370 controls. After adjustments for traditional risk factors, the two highest tertiles of PTX3 and the highest tertiles of ficolin-2 and MASP-3 were associated with MI, with odds ratios (95% confidence interval) of 1.65 (1.10-2.47) and 2.79 (1.83-4.24) for PTX3, 1.55 (1.04-2.30) for ficolin-2, and 0.63 (0.043-0.94) for MASP-3. Ficolin-1, ficolin-3 and MAP-1 were not associated with MI. In a multimarker analysis of all associated biomarkers, only PTX3 and MASP-3 remained significant. PTX-3 and MASP-3 enhanced prediction of MI compared to the traditional Framingham risk score alone (AUC increased from 0.64 to 0.68, p = 0.006). These results support the role of complement-dependent inflammation in the pathophysiology of cardiovascular disease.

Complement Protein C1q Enhances Macrophage Foam Cell Survival and Efferocytosis

In the atherosclerotic lesion, macrophages ingest high levels of damaged modified low-density lipoproteins (LDLs), generating macrophage foam cells. Foam cells undergo apoptosis and, if not efficiently cleared by efferocytosis, can undergo secondary necrosis, leading to plaque instability and rupture. As a component of the innate immune complement cascade, C1q recognizes and opsonizes modified forms of LDL, such as oxidized or acetylated LDL, and promotes ingestion by macrophages in vitro. C1q was shown to be protective in an atherosclerosis model in vivo. Therefore, this study aimed to investigate whether ingestion of modified LDL in the presence of C1q alters macrophage foam cell survival or function. In an unbiased transcriptome analysis, C1q was shown to modulate expression of clusters of genes involved in cell death and apoptosis pathways in human monocyte-derived macrophages ingesting modified LDL; this was validated by quantitative PCR in human and murine macrophages. C1q downregulated levels and activity of active caspase-3 and PARP-1 in human and mouse macrophages during ingestion of modified LDL. This led to a measurable increase in survival and decrease in cell death, as measured by alamarBlue and propidium iodide assays, respectively. C1q opsonization also increased phagocytosis and efferocytosis in macrophage foam cells. These data suggest that C1q promotes macrophage survival during ingestion of excess cholesterol, as well as improves foam cell efferocytic function. This may be important in slowing disease progression and provides insight into the protective role of C1q in early atherosclerosis.

Platelets and platelet adhesion molecules: novel mechanisms of thrombosis and anti-thrombotic therapies

Platelets are central mediators of thrombosis and hemostasis. At the site of vascular injury, platelet accumulation (i.e. adhesion and aggregation) constitutes the first wave of hemostasis. Blood coagulation, initiated by the coagulation cascades, is the second wave of thrombin generation and enhance phosphatidylserine exposure, can markedly potentiate cell-based thrombin generation and enhance blood coagulation. Recently, deposition of plasma fibronectin and other proteins onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that occurs prior to platelet accumulation (i.e. the classical first wave of hemostasis). These three waves of hemostasis, in the event of atherosclerotic plaque rupture, may turn pathogenic, and cause uncontrolled vessel occlusion and thrombotic disorders (e.g. heart attack and stroke). Current anti-platelet therapies have significantly reduced cardiovascular mortality, however, on-treatment thrombotic events, thrombocytopenia, and bleeding complications are still major concerns that continue to motivate innovation and drive therapeutic advances. Emerging evidence has brought platelet adhesion molecules back into the spotlight as targets for the development of novel anti-thrombotic agents. These potential antiplatelet targets mainly include the platelet receptors glycoprotein (GP) Ib-IX-V complex, β3 integrins (αIIb subunit and PSI domain of β3 subunit) and GPVI. Numerous efforts have been made aiming to balance the efficacy of inhibiting thrombosis without compromising hemostasis. This mini-review will update the mechanisms of thrombosis and the current state of antiplatelet therapies, and will focus on platelet adhesion molecules and the novel anti-thrombotic therapies that target them.

Evaluation of the anti-inflammatory activities of tanshinones isolated from Salvia miltiorrhiza var. alba roots in THP-1 macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza var. alba roots are used as the Chinese traditional medicine Danshen for the treatment of cardiovascular diseases in local clinical practice. Tanshinones are the major effective constituents of S. miltiorrhiza var. alba roots, but only tanshinone IIA, tanshinone I, cryptotanshinone, and 15,16-dihydrotanshinone have been investigated for their anti-inflammatory activities.

MATERIALS AND METHODS

Eleven known compounds were isolated from S. miltiorrhiza var. alba roots, and the structures of all compounds were elucidated by spectroscopic analysis and comparisons with reported data. Immune anti-inflammatory activities were assessed by the ability to inhibit the production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and interleukin (IL)-8 using enzyme-linked immunosorbent assay. Quantitative real-time polymerase chain reaction (qRT-PCR) was also used to compare the inhibitory effects of the compounds on TNF-α, IL-1β, and IL-8 mRNA expression with that of tanshinone IIA in lipopolysaccharide-stimulated THP-1 macrophages.

RESULTS

All tanshinones, except for compound 5, significantly inhibited the mRNA and protein expression of TNF-α, IL-1β, and IL-8, and their anti-inflammatory activities were stronger than that of tanshinone IIA. Compound 9 (5μM) showed the highest inhibitory effects for TNF-α, IL-1β, and IL-8, at 56.3%, 67.6%, and 51.7%, respectively.

CONCLUSIONS

Ten of the 11 tanshinones were shown to have anti-inflammatory properties superior to those of TSIIA, and which significantly inhibited the expression of TNF-α, IL-1β, and IL-8. The present results provided a referential basis for explaining the use of S. miltiorrhiza var. alba root as a Chinese folk medicine for treating cardiovascular diseases associated with inflammation, and show the importance of trace constituents of this herb.

Proinflammatory proteins in female and male patients with primary antiphospholipid syndrome: preliminary data

The latest classification criteria for the diagnosis of the antiphospholipid syndrome (APS, an autoimmune disease characterized by thromboses, miscarriages and presence of antiphospholipid antibodies (Abs)) emphasized that thrombotic manifestations of APS should be without any signs of an inflammatory process. However, atherosclerosis (a chronic inflammatory response to the accumulation of lipoproteins in the walls of arteries) and APS are characterized by some similar features. We evaluated whether proinflammatory proteins were associated with the features of the primary APS (PAPS). PAPS patients without obstetric complications and with impaired lipid profile were included in the study. Antiphospholipid antibodies, TNF-alpha, and apo(a) were determined by ELISA. Complement components and hsCRP were measured by immunonephelometry. Decreased C3c was observed in female patients with increased titers of IgG anti-β2gpI (χ(2) = 3.939, P = 0.047) and in male patients with increased IgM anticardiolipin Abs (χ(2) = 4.286, P = 0.038). Pulmonary emboli were associated with interleukin (IL)-6 in male (χ(2) = 6.519, P = 0.011) and in female (χ(2) = 10.405, P = 0.001) patients. Cerebrovascular insults were associated with LDL-cholesterol (P = 0.05, 95 % CI: 1.003 - 12.739) in female and with apo(a) (P = 0.016, 95 % CI: 0.000-0.003) in male patients. Older female patients had increased LDL-cholesterol levels and frequency of myocardial infarctions. Proinflammatory proteins were associated with features of primary APS. No real gender differences in regard to proinflammatory protein levels were observed. Premenopausal state of female PAPS patients confers lower cardiovascular risk.

Is ischemia modified albumin a disease activity marker for inflammatory bowel diseases?

BACKGROUND AND AIM

We aimed to identify ischemia-modified albumin (IMA) levels in inflammatory bowel disease (IBD) and IBD subgroups, and to examine its relation with disease activity index.

METHODS

Sixty-eight patients with IBD (35 ulcerative colitis [UC] and 33 crohn disease [CD]) and 65 healthy volunteers were included in the study. Rachmilewitz scoring system (endoscopic activity index [EAI]) was used to determine UC activity, and as for CD activity, CD activity index (CDAI) scoring was used. IMA measurement was performed with ELISA kit.

RESULTS

Ischemia-modified albumin levels in IBD, UC, and CD groups were comparably higher than the control group (37.7 ng/mL vs 42.4 ng/mL vs 36.4 ng/mL vs 21.8 ng/mL, respectively; P < 0.05). In IBD group, a positive correlation was identified between IMA level and CRP (r = 0.325, P = 0.011), EAI(r = 0.302, P = 0.020), and CDAI (r = 0.311, P = 0.013). In stepwise regression model; it was identified that IMA(OR = 1.496; P = 0.016) and CRP(OR = 3.457; P = 0.015) are predictors of IBD in comparison with the control group. In linear regression model, it was identified that risk factors such as log(IMA) and log(CRP) were independent predictors of log(CDAI) and log(EAI) levels.

CONCLUSION

This is the first study showing that IMA levels in IBD were determined higher in comparison with the control group. Moreover, IMA being a predictor for IBD and being positively correlated with disease activity indexes were determined for the first time in the study. In accordance with these results, it is possible to say that IMA in IBD might be related with the pathogenesis of disease and correlated with the severity of the disease.

New milestones ahead in complement-targeted therapy

The complement system is a powerful effector arm of innate immunity that typically confers protection from microbial intruders and accumulating debris. In many clinical situations, however, the defensive functions of complement can turn against host cells and induce or exacerbate immune, inflammatory, and degenerative conditions. Although the value of inhibiting complement in a therapeutic context has long been recognized, bringing complement-targeted drugs into clinical use has proved challenging. This important milestone was finally reached a decade ago, yet the clinical availability of complement inhibitors has remained limited. Still, the positive long-term experience with complement drugs and their proven effectiveness in various diseases has reinvigorated interest and confidence in this approach. Indeed, a broad variety of clinical candidates that act at almost any level of the complement activation cascade are currently in clinical development, with several of them being evaluated in phase 2 and phase 3 trials. With antibody-related drugs dominating the panel of clinical candidates, the emergence of novel small-molecule, peptide, protein, and oligonucleotide-based inhibitors offers new options for drug targeting and administration. Whereas all the currently approved and many of the proposed indications for complement-targeted inhibitors belong to the rare disease spectrum, these drugs are increasingly being evaluated for more prevalent conditions. Fortunately, the growing experience from preclinical and clinical use of therapeutic complement inhibitors has enabled a more evidence-based assessment of suitable targets and rewarding indications as well as related technical and safety considerations. This review highlights recent concepts and developments in complement-targeted drug discovery, provides an overview of current and emerging treatment options, and discusses the new milestones ahead on the way to the next generation of clinically available complement therapeutics.

Complement in disease: a defence system turning offensive

Although the complement system is primarily perceived as a host defence system, a more versatile, yet potentially more harmful side of this innate immune pathway as an inflammatory mediator also exists. The activities that define the ability of the complement system to control microbial threats and eliminate cellular debris - such as sensing molecular danger patterns, generating immediate effectors, and extensively coordinating with other defence pathways - can quickly turn complement from a defence system to an aggressor that drives immune and inflammatory diseases. These host-offensive actions become more pronounced with age and are exacerbated by a variety of genetic factors and autoimmune responses. Complement can also be activated inappropriately, for example in response to biomaterials or transplants. A wealth of research over the past two decades has led to an increasingly finely tuned understanding of complement activation, identified tipping points between physiological and pathological behaviour, and revealed avenues for therapeutic intervention. This Review summarizes our current view of the key activating, regulatory, and effector mechanisms of the complement system, highlighting important crosstalk connections, and, with an emphasis on kidney disease and transplantation, discusses the involvement of complement in clinical conditions and promising therapeutic approaches.

The Neuroprotective Effect of Rapamycin as a Modulator of the mTOR-NF-κB Axis during Retinal Inflammation

Purpose

The determination of the molecular mechanism underlying retinal pathogenesis and visual dysfunction during innate inflammation, and the treatment effect of rapamycin thereon.

Methods

The endotoxin-induced uveitis and retinitis mouse model was established by injecting lipopolysaccharide. The mice were subsequently treated with rapamycin, a mammalian target of rapamycin (mTOR) inhibitor. The rhodopsin mRNA and protein expression level in the retina and the photoreceptor outer segment (OS) length in immunohistochemical stainings were measured, and visual function was recorded by electroretinography. Inflammatory cytokines, their related molecules, mTOR, and LC3 levels were measured by real-time PCR and/or immunoblotting. Leukocyte adhesion during inflammation was analyzed using concanavalin A lectin.

Results

The post-transcriptional reduction in the visual pigment of rod photoreceptor cells, rhodopsin, OS shortening, and rod photoreceptor cell dysfunction during inflammation were suppressed by rapamycin. Activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and induction of inflammatory cytokines, such as interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), and the activation of the downstream signaling protein, signal transducer and activator of transcription 3 (STAT3), which reduces rhodopsin in the retina during inflammation, were attenuated by rapamycin. Increased leukocyte adhesion was also attenuated by rapamycin. Interestingly, although mTOR activation was observed after NF-κB activation, mTOR inhibition suppressed NF-κB activation at the early phase, indicating that the basal level of activated mTOR was sufficient to activate NF-κB in the retina. In addition, the inhibition of NF-κB suppressed mTOR activation, suggesting a positive feedback loop of mTOR and NF-κB during inflammation. The ratio of LC3II to LC3I, which reflects autophagy induction, was not changed by inflammation but was increased by rapamycin.

Conclusions

Our results propose the potential use of rapamycin as a neuroprotective therapy to suppress local activated mTOR levels, related inflammatory molecules, and the subsequent visual dysfunction during retinal inflammation.

Efficacy and Safety of Paclitaxel-Coated Balloon for the Treatment of In-Stent Restenosis in High-Risk Patients

In-stent restenosis (ISR) is a major cause of failure of percutaneous coronary intervention. The efficacy and safety of drug-coated balloon (DCB) in patients with high-risk clinical features are largely unknown. We enrolled 82 consecutive patients at high risk of bleeding with angiographically significant (diameter stenosis ≥ 50%) ISR of bare metal stent (BMS) or drug-eluting stent (DES), treated with paclitaxel-coated balloon. All patients presented at least one of the following criteria: high bleeding risk, neoplasm, chronic inflammatory disease, and need for noncardiac surgery. Dual antiplatelet therapy was indicated for 4 weeks after the procedure. At angiographic follow-up, overall late lumen loss was 0.24 ± 0.32 mm, with no significant difference between BMS-ISR and DES-ISR (0.25 ± 0.35 vs 0.22 ± 0.30 mm, p = 0.714). The Kaplan-Meier estimate for major adverse clinical events-free survival at 3 years was 81.4% (82.3% in BMS-ISR vs 79.4% in DES-ISR, log-rank p = 0.866). No stent thrombosis has been recorded. In conclusion, the use of paclitaxel-coated balloon seems to be associated with favorable outcomes after percutaneous coronary intervention for BMS-ISR or DES-ISR in patients with high-risk clinical features and could be considered as a reasonable option in the presence of systemic co-morbidities and contraindications to long-term dual antiplatelet therapy.