Colocalisation of intraplaque C reactive protein, complement, oxidised low density lipoprotein, and macrophages in stable and unstable angina and acute myocardial infarction

Modification of lipoprotein metabolism and function driving atherogenesis in diabetes

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease, characterized by raised blood glucose levels and impaired lipid metabolism resulting from insulin resistance and relative insulin deficiency. In diabetes, the peculiar plasma lipoprotein phenotype, consisting in higher levels of apolipoprotein B-containing lipoproteins, hypertriglyceridemia, low levels of HDL cholesterol, elevated number of small, dense LDL, and increased non-HDL cholesterol, results from an increased synthesis and impaired clearance of triglyceride rich lipoproteins. This condition accelerates the development of the atherosclerotic cardiovascular disease (ASCVD), the most common cause of death in T2DM patients. Here, we review the alteration of structure, functions, and distribution of circulating lipoproteins and the pathophysiological mechanisms that induce these modifications in T2DM. The review analyzes the influence of diabetes-associated metabolic imbalances throughout the entire process of the atherosclerotic plaque formation, from lipoprotein synthesis to potential plaque destabilization. Addressing the different pathophysiological mechanisms, we suggest improved approaches for assessing the risk of adverse cardiovascular events and clinical strategies to reduce cardiovascular risk in T2DM and cardiometabolic diseases.

C-reactive protein deficiency ameliorates experimental abdominal aortic aneurysms

Background

C-reactive protein (CRP) levels are elevated in patients with abdominal aortic aneurysms (AAA). However, it has not been investigated whether CRP contributes to AAA pathogenesis.

Methods

CRP deficient and wild type (WT) male mice were subjected to AAA induction via transient intra-aortic infusion of porcine pancreatic elastase. AAAs were monitored by in situ measurements of maximal infrarenal aortic external diameters immediately prior to and 14 days following elastase infusion. Key AAA pathologies were assessed by histochemical and immunohistochemical staining procedures. The influence of CRP deficiency on macrophage activation was evaluated in peritoneal macrophages in vitro.

Results

CRP protein levels were higher in aneurysmal than that in non-aneurysmal aortas. Aneurysmal aortic dilation was markedly suppressed in CRP deficient (aortic diameter: 1.08 ± 0.11 mm) as compared to WT (1.21 ± 0.08 mm) mice on day 14 after elastase infusion. More medial elastin was retained in CRP deficient than in WT elastase-infused mice. Macrophage accumulation was significantly less in aneurysmal aorta from CRP deficient than that from WT mice. Matrix metalloproteinase 2 expression was also attenuated in CRP deficient as compared to WT aneurysmal aortas. CRP deficiency had no recognizable influence on medial smooth muscle loss, lymphocyte accumulation, aneurysmal angiogenesis, and matrix metalloproteinase 9 expression. In in vitro assays, mRNA levels for tumor necrosis factor α and cyclooxygenase 2 were reduced in lipopolysaccharide activated peritoneal macrophages from CRP deficient as compared to wild type mice.

Conclusion

CRP deficiency suppressed experimental AAAs by attenuating aneurysmal elastin destruction, macrophage accumulation and matrix metalloproteinase 2 expression.

Calcium-dependent reversible coaggregation activity of C-reactive protein and M-ficolin

C-reactive protein (CRP) and M-ficolin are the pattern recognition proteins of the innate immune system. In this report, a mixture of CRP and M-ficolin reversibly co-aggregated in a calcium-dependent manner. This coaggregation was enhanced at low pH (6.5) or low salt (35 mM NaCl) concentrations. The co-aggregate was dissolved by adding EDTA and reformed by adding calcium. The M-ficolin fibrinogen-like domain (FD1), the ligand-binding domain of M-ficolin, also showed calcium-dependent coaggregation with CRP, indicating that reversible coaggregation is caused by CRP interacting with FD1. Interestingly, adding phosphocholine (PC), the ligand of CRP, to a CRP-FD1 mixture abolished the reversible coaggregation activity. PC also inhibited the interaction between CRP and FD1. These results indicate that CRP retains PC-binding activity in the coaggregation state and that FD1 binds specifically to the PC-binding site on CRP but does not fully occupy the five PC-binding sites on a CRP pentamer as judged by SDS-PAGE analysis of precipitates. Coaggregation analysis using FD1 mutants showed that FD1 also retains ligand-binding activity in the coaggregation state and that coaggregation requires the trimeric form of FD1. It was also found that modifications to the ligand-binding site of FD1 affect coaggregation efficiency. Although the biological functions of the coaggregation activity of CRP and M-ficolin remain unresolved, the co-aggregates may function as bacteria-trapping particles with affinities for ligands of CRP and M-ficolin. In addition, coaggregation may be involved in CRP deposition in the lesions of several arterial diseases, such as atherosclerosis.

Transitional changes in the structure of C-reactive protein create highly pro-inflammatory molecules: Therapeutic implications for cardiovascular diseases

C-reactive protein (CRP) is the prototypic acute-phase reactant that has long been recognized almost exclusively as a marker of inflammation and predictor of cardiovascular risk. However, accumulating evidence indicates that CRP is also a direct pathogenic pro-inflammatory mediator in atherosclerosis and cardiovascular diseases. The 'CRP system' consists of at least two protein conformations with distinct pathophysiological functions. The binding of the native, pentameric CRP (pCRP) to activated cell membranes leads to a conformational change resulting in two highly pro-inflammatory isoforms, pCRP* and monomeric CRP (mCRP). The deposition of these pro-inflammatory isoforms has been shown to aggravate the localized tissue injury in a broad range of pathological conditions including atherosclerosis and thrombosis, myocardial infarction, and stroke. Here, we review recent findings on how these structural changes contribute to the inflammatory response and discuss the transitional changes in the structure of CRP as a novel therapeutic target in cardiovascular diseases and overshooting inflammation.

Characteristic of cardiovascular status and intracardiac hemodynamics in patients with multiple myeloma before the start of antitumor therapy

AIM

assessment of risk factors, cardiovascular status and intracardiac hemodynamics in patients with multiple myeloma before the start of specific antitumor therapy. Materials and methods: The study included 2 equal groups of patients: the first group - 25 patients with a newly diagnosed diagnosis of multiple myeloma (MM), the comparison group - 25 patients with proven cardiovascular diseases (CVD) (hypertension (HD) and coronary heart disease (CHD)). All patients included in the study underwent standard laboratory diagnostics, instrumental research methods (ECG, Echo-KG, 24-hour Holter monitoring); proven CVD risk factors were also evaluated. Results: When comparing the two groups, it was reliably shown that the state of CVD in patients with MM is comparable to that in patients with proven CVD. In patients from the main group, were revealed significant positive correlations of average strength between indicators of systemic inflammation, the lipid spectrum and intracardiac hemodynamics: between the levels of CRP and triglycerides (r=0,415, p<0,05); between the values of CRP and LDL (r=0,345, p=0,09); CRP and LA volume (r=0,434, p<0,05); CRP and final diastolic volume (r=0,30, p<0,05). At the beginning, a high risk of developing CV- events in patients with MM may be due to cardiac remodeling associated with the activity of systemic inflammation.

CONCLUSION

in view the use of potentially cardiovasculartoxicity drugs for the treatment of multiple myeloma, the assessment of the CV status and consultation with a cardiologist/cardiologist with the selection of the necessary therapy should be obligatory step before starting specific treatment.

A Sorbent with Synthetic Ligand for Removing Pro-atherogenic and Pro-inflammatory Components from Human Blood Plasma

Elevated levels of apoB-100 containing lipoproteins and markers of systemic inflammation are often observed in patients with cardiovascular diseases. The concentrations can be reduced by pharmacotherapy or extracorporeal treatment. The sorbent, which removes CRP and atherogenic lipoproteins, simultaneously reduces the bloodstream concentration of these components. The efficacy and selectivity of the designed sorbent were studied, desorption constants of CRP (Kd = 4.2 × 10-8 M) and LDL (Kd = 7.7 × 10-7 M) were distribution coefficients of CRP (Kc = 101) and Lp(a) (Kc = 38) were calculated, and the ability to bind large amounts of atherogenic lipoproteins (up to 32 mg of TC per mL of the sorbent gel) was demonstrated. Our sorbent can be recommended for performing complex removal of CRP and atherogenic lipoproteins from the blood plasma in patients with refractory hyperlipidemia and CVD that are accompanied by elevated levels of CRP.

Complement Inhibition Targeted to Injury Specific Neoepitopes Attenuates Atherogenesis in Mice

Rationale: Previous studies have indicated an important role for complement in atherosclerosis, a lipid-driven chronic inflammatory disease associated to oxidative stress in the vessel wall. However, it remains unclear how complement is activated in the process of atherogenesis. An accepted general model for complement activation in the context of ischemia reperfusion injury is that ischemia induces the exposure of neoepitopes that are recognized by natural self-reactive IgM antibodies, and that in turn activate complement. Objective: We investigated whether a similar phenomenon may be involved in the pathogenesis of atherosclerosis, and whether interfering with this activation event, together with inhibition of subsequent amplification of the cascade at the C3 activation step, can provide protection against atherogenesis. Methods and Results: We utilized C2scFv-Crry, a novel construct consisting of a single chain antibody (scFv) linked to Crry, a complement inhibitor that functions at C3 activation. The scFv moiety was derived from C2 IgM mAb that specifically recognizes phospholipid neoepitopes known to be expressed after ischemia. C2scFv-Crry targeted to the atherosclerotic plaque of Apoe -/- mice, demonstrating expression of the C2 neoepitope. C2scFv-Crry administered twice per week significantly attenuated atherosclerotic plaque in the aorta and aortic root of Apoe -/- mice fed with a high-fat diet (HFD) for either 2 or 4 months, and treatment reduced C3 deposition and membrane attack complex formation as compared to vehicle treated mice. C2scFv-Crry also inhibited the uptake of oxidized low-density-lipoprotein (oxLDL) by peritoneal macrophages, which has been shown to play a role in pathogenesis, and C2scFv-Crry-treated mice had decreased lipid content in the lesion with reduced oxLDL levels in serum compared to vehicle-treated mice. Furthermore, C2scFv-Crry reduced the deposition of endogenous total IgM in the plaque, although it did not alter serum IgM levels, further indicating a role for natural IgM in initiating complement activation. Conclusion: Neoepitope targeted complement inhibitors represent a novel therapeutic approach for atherosclerosis.

Novel molecular markers of cardiovascular disease risk in type 2 diabetes mellitus

Diabetes represents the leading risk factor for the development of cardiovascular disease (CVD). Chronic hyperglycemia and/or acute post-prandial changes in blood glucose determine an increase in reactive oxygen species (ROS), which play a fundamental role in endothelial dysfunction and in the nuclear transport of pro-atherogenic transcription factors that activate the "inflammasome". In addition, the glycemic alteration favors the formation and stabilization of atherosclerotic plaque through the mechanism of non-enzymatic glycation of different molecules, with the establishment of the so-called "advanced glycosylation end products" (AGE). Laboratory information provided by the level of biomarkers could make a quantitative and qualitative contribution to the clinical process of screening, prediction, prevention, diagnosis, prognosis and monitoring of cardiovascular (CV) risk linked to diabetes. This review describes the importance of specific biomarkers, with particular focus on novel ones, for stratifying and management of diabetes CV risk.

Therapeutic Lowering of C-Reactive Protein

In the blood of healthy individuals C-reactive protein (CRP) is typically quite scarce, whereas its blood concentration can rise robustly and rapidly in response to tissue damage and inflammation associated with trauma and infectious and non-infectious diseases. Consequently, CRP plasma or serum levels are routinely monitored in inpatients to gauge the severity of their initial illness and injury and their subsequent response to therapy and return to health. Its clinical utility as a faithful barometer of inflammation notwithstanding, it is often wrongly concluded that the biological actions of CRP (whatever they may be) are manifested only when blood CRP is elevated. In fact over the last decades, studies done in humans and animals (e.g. human CRP transgenic and CRP knockout mice) have shown that CRP is an important mediator of biological activities even in the absence of significant blood elevation, i.e. even at baseline levels. In this review we briefly recap the history of CRP, including a description of its discovery, early clinical use, and biosynthesis at baseline and during the acute phase response. Next we overview evidence that we and others have generated using animal models of arthritis, neointimal hyperplasia, and acute kidney injury that baseline CRP exerts important biological effects. In closing we discuss the possibility that therapeutic lowering of baseline CRP might be a useful way to treat certain diseases, including cancer.

Urotensin-II, oxidative stress, and inflammation increase in hypertensive and resistant hypertensive patients

Objective: Hypertension is a multi-factorial process prevalent in developed as well as in developing countries. Urotensin-II, different antioxidants, free radicals, and inflammatory biomarkers play an essential role in the cardiovascular system. The aim of this study is to investigate Urotensin-II, oxidative stress, and inflammation markers in normotensive, hypertensive, and resistant hypertensive patients. Methods: Fifty resistance hypertensive (rHT) patients, 50 hypertensive patients, and 50 age gender matched normotensive controls (NT-control) were enrolled. Urotensin-II (UII), total oxidant status (TOS), total antioxidant status (TAS), native thiol (NT), total thiol (TT), disulfide (DIS), interleukin 1 beta (IL1β), interleukin 6 (IL6), tumor necrosis factor-alpha (TNFα), high sensitive c reactive protein (hsCRP), high-density lipoprotein (HDL) low-density lipoprotein (LDL), and total cholesterol (TC) were evaluated. Results: Serum levels of UII, IL1β, IL6, TNFα, DIS, TOS, and OSI were found higher in rHT and HT as compared to NT-control (p < .001). On the contrary, serum levels of TT, TAS, and NT were lower in rHT and HT as compared to NT-control (p < .001). While TC, hsCRP, TOS, OSI, UII, IL1β, IL6, and TNFα levels increase from HT to rHT group (p < .001); TAS and NT levels decrease from HT to rHT group (p < .001). Conclusions: UII levels, oxidative stress, and inflammation are higher in rHT and HT, while antioxidants and thiol levels are lower than the NT-control. Our study clearly showed that rHT and HT are more susceptible to impaired states of antioxidants, oxidative stress, and free radicals.

Membrane Attack Complex in Myocardial Ischemia/Reperfusion Injury: A Systematic Review for Post Mortem Applications

The complement system has a significant role in myocardial ischemia/reperfusion injury, being responsible for cell lysis and amplification of inflammatory response. In this context, several studies highlight that terminal complement complex C5b-9, also known as the membrane attack complex (MAC), is a significant contributor. The MAC functions were studied by many researchers analyzing the characteristics of its activation in myocardial infarction. Here, a systematic literature review was reported to evaluate the principal features, advantages, and limits (regarding the application) of complement components and MAC in post mortem settings to perform the diagnosis of myocardial ischemia/infarction. The review was performed according to specific inclusion and exclusion criteria, and a total of 26 studies were identified. Several methods studied MAC, and each study contributes to defining better how and when it affects the myocardial damage in ischemic/reperfusion injury. The articles were discussed, focusing on the specificity, sensibility, and post mortem stability of MAC as a marker of myocardial ischemia/infarction, supporting the usefulness in routine post mortem investigations.

Cholesterol crystals use complement to increase NLRP3 signaling pathways in coronary and carotid atherosclerosis

BACKGROUND

During atherogenesis, cholesterol precipitates into cholesterol crystals (CC) in the vessel wall, which trigger plaque inflammation by activating the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome. We investigated the relationship between CC, complement and NLRP3 in patients with cardiovascular disease.

METHODS

We analysed plasma, peripheral blood mononuclear cells (PBMC) and carotid plaques from patients with advanced atherosclerosis applying ELISAs, multiplex cytokine assay, qPCR, immunohistochemistry, and gene profiling.

FINDINGS

Transcripts of interleukin (IL)-1beta(β) and NLRP3 were increased and correlated in PBMC from patients with acute coronary syndrome (ACS). Priming of these cells with complement factor 5a (C5a) and tumour necrosis factor (TNF) before incubation with CC resulted in increased IL-1β protein when compared to healthy controls. As opposed to healthy controls, systemic complement was significantly increased in patients with stable angina pectoris or ACS. In carotid plaques, complement C1q and C5b-9 complex accumulated around CC-clefts, and complement receptors C5aR1, C5aR2 and C3aR1 were higher in carotid plaques compared to control arteries. Priming human carotid plaques with C5a followed by CC incubation resulted in pronounced release of IL-1β, IL-18 and IL-1α. Additionally, mRNA profiling demonstrated that C5a and TNF priming followed by CC incubation upregulated plaque expression of NLRP3 inflammasome components.

INTERPRETATION

We demonstrate that CC are important local- and systemic complement activators, and we reveal that the interaction between CC and complement could exert its effect by activating the NLRP3 inflammasome, thus promoting the progression of atherosclerosis.

Association between periodontal disease and vulnerable plaque morphology in patients undergoing carotid endarterectomy

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Periodontal disease is associated with echolucent plaques.

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Periodontal disease is associated with increased macrophages in plaques.

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Periodontal disease is associated with decreased smooth muscle cells in plaques.

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Periodontal disease is associated with plaque instability.

Background

Periodontal disease (PD) is a chronic inflammatory oral condition with potentially important systemic sequelae. We sought to determine whether the presence of PD in patients with severe carotid disease was associated with morphological features consistent with carotid plaque instability.

Methods

A total of 52 dentate patients hospitalized for carotid endarterectomy (CEA) had standardized assessments of their periodontal status, including measurements of probing pocket depth (PPD), clinical attachment level (CAL) and bleeding on probing (BoP). Carotid plaque morphology was assessed by ultrasound using the gray scale median (GSM) score and by immunohistochemistry using anti-CD68 and anti-alpha-actin antibodies, markers for macrophages and smooth muscle cells (SMCs) respectively.

Results

In total 30/52 patients (58%) had PD. Significant associations were noted between low GSM on ultrasound and each mm in PPD (p = 0.001), each mm in CAL (p = 0.002) and with a 10% increase in BoP (p = 0.009). Using the standardized PERIO definition the association remained robust (aOR = 10.4 [95% CI:2.3–46.3], p = .002). Significant associations were also observed with high macrophage accumulation and each individual PD measure (p < 0.01 for PPD, CAL and BoP) and with the PERIO definition (aOR = 15 [95% CI:1.8–127.8], p = .01). Similarly, low SMC density was also significantly associated with individual measures of PD (p < 0.05 for PPD, CAL and BoP), but not with the PERIO definition (aOR 3.4 [95% CI:0.9–12.8], p = .07).

Conclusions

The presence of PD was significantly associated with both ultrasound and immunohistochemistry features of carotid plaque instability in patients undergoing CEA.

Inflammatory changes in the aneurysm wall: a review

Rupture of a saccular intracranial artery aneurysm (IA) causes subarachnoid hemorrhage, a significant cause of stroke and death. The current treatment options, endovascular coiling and clipping, are invasive and somewhat risky. Since only some IAs rupture, those IAs at risk for rupture should be identified. However, to improve the imaging of rupture-prone IAs and improve IA treatment, IA wall pathobiology requires more thorough knowledge. Chronic inflammation has become understood as an important phenomenon in IA wall pathobiology, featuring inflammatory cell infiltration as well as proliferative and fibrotic remodulatory responses. We review the literature on what is known about inflammation in the IA wall and also review the probable mechanisms of how inflammation would result in the degenerative changes that ultimately lead to IA wall rupture. We also discuss current options in imaging inflammation and how knowledge of inflammation in IA walls may improve IA treatment.

Dissociation of C-Reactive Protein Localizes and Amplifies Inflammation: Evidence for a Direct Biological Role of C-Reactive Protein and Its Conformational Changes

C-reactive protein (CRP) is a member of the pentraxin superfamily that is widely recognized as a marker of inflammatory reactions and cardiovascular risk in humans. Recently, a growing body of data is emerging, which demonstrates that CRP is not only a marker of inflammation but also acts as a direct mediator of inflammatory reactions and the innate immune response. Here, we critically review the various lines of evidence supporting the concept of a pro-inflammatory “CRP system.” The CRP system consists of a functionally inert circulating pentameric form (pCRP), which is transformed to its highly pro-inflammatory structural isoforms, pCRP* and ultimately to monomeric CRP (mCRP). While retaining an overall pentameric structure, pCRP* is structurally more relaxed than pCRP, thus exposing neoepitopes important for immune activation and complement fixation. Thereby, pCRP* shares its pro-inflammatory properties with the fully dissociated structural isoform mCRP. The dissociation of pCRP into its pro-inflammatory structural isoforms and thus activation of the CRP system occur on necrotic, apoptotic, and ischemic cells, regular β-sheet structures such as β-amyloid, the membranes of activated cells (e.g., platelets, monocytes, and endothelial cells), and/or the surface of microparticles, the latter by binding to phosphocholine. Both pCRP* and mCRP can cause activation of platelets, leukocytes, endothelial cells, and complement. The localization and deposition of these pro-inflammatory structural isoforms of CRP in inflamed tissue appear to be important mediators for a range of clinical conditions, including ischemia/reperfusion (I/R) injury of various organs, cardiovascular disease, transplant rejection, Alzheimer’s disease, and age-related macular degeneration. These findings provide the impetus to tackle the vexing problem of innate immunity response by targeting CRP. Understanding the “activation process” of CRP will also likely allow the development of novel anti-inflammatory drugs, thereby providing potential new immunomodulatory therapeutics in a broad range of inflammatory diseases.

Complement activation in the arteries of patients with severe atherosclerosis

BACKGROUND

Excessive complement activation plays an important role in the pathogenesis of atherosclerosis (AS). We therefore wanted to investigate whether complement is activated in areas of AS by detecting the deposition of C3b/iC3b and membrane attack complex (MAC). We also analyzed the relationships between C3b/iC3b and MAC levels and the clinicopathological features of patients with AS.

METHODS

The sample comprised 79 patients who had been diagnosed with AS. Their levels of C3b/iC3b and MAC deposition were evaluated by immunohistochemistry (IHC). The results were translated into scores, and the patients' clinical features were recorded.

RESULTS

Compared with normal arteries, significantly greater deposits of C3b/iC3b and MAC were found in AS arteries. In the group with more C3b/iC3b deposition, the ratio of patients with hypertension was higher. Moreover, in the group with more MAC deposition, the ratio of patients with hypertriglyceridemia was higher.

CONCLUSIONS

The finding of C3b/iC3b and MAC deposition in atherosclerotic arteries points to the activation of complement. Greater amounts of C3b/iC3b and MAC deposition imply excessive complement activation, which can lead to the development of AS. Hypertension and hypertriglyceridemia may, respectively, contribute to the activation of complement C3 or the formation of MAC.

Platelets, inflammation and anti-inflammatory effects of antiplatelet drugs in ACS and CAD

Platelets play a pivotal role in chronic inflammation leading to progression of atherosclerosis and acute coronary events. Recent discoveries on novel mechanisms and platelet-dependent inflammatory targets underpin the role of platelets to maintain a chronic inflammatory condition in cardiovascular disease. There is strong and clinically relevant crosslink between chronic inflammation and platelet activation. Antiplatelet therapy is a cornerstone in the prevention and treatment of acute cardiovascular events. The benefit of antiplatelet agents has mainly been attributed to their direct anti-aggregatory impact. Some anti-inflammatory off-target effects have also been described. However, it is unclear whether these effects are secondary due to inhibition of platelet activation or are caused by direct distinct mechanisms interfering with inflammatory pathways. This article will highlight novel platelet associated targets that contribute to inflammation in cardiovascular disease and elucidate mechanisms by which currently available antiplatelet agents evolve anti-inflammatory capacities, in particular by carving out the differential mechanisms directly or indirectly affecting platelet mediated inflammation. It will further illustrate the prognostic impact of antiplatelet therapies by reducing inflammatory marker release in recent cardiovascular trials.

Vascular inflammation and low-density lipoproteins: is cholesterol the link? A lesson from the clinical trials

For long time, the role of LDL and inflammation in the pathogenesis of atherosclerosis have been studied independently from each other and only more recently a common platform has been suggested. Accumulation of excess cholesterol due to the presence of increased circulating LDL promotes endothelium dysfunction and activation, which is associated with increased production of pro-inflammatory cytokines, overexpression of adhesion molecules, chemokines and C-reactive protein (CRP), increased generation of reactive oxygen species and reduction of nitric oxide levels and bioavailability. All these processes favour the progressive infiltration of inflammatory cells within the arterial wall where cholesterol accumulates, both extracellularly and intracellularly, and promotes vascular inflammation. According to this, lipid-lowering therapies should improve inflammation and, indeed, statins decrease circulating inflammatory markers such as CRP and improve endothelial function and plaque burden. Pleiotropic activities have been proposed to explain this effect. However, mendelian randomization studies ruled out a direct role for CRP on coronary artery disease and studies with other lipid lowering drugs, such as ezetimibe showed that the beneficial effect of LDL-cholesterol-lowering therapies on systemic inflammatory status, as monitored by changes in CRP plasma levels, could be achieved, independently of the mechanism of action, only in patients presenting with baseline inflamed conditions. These observations strengthen the direct link between cholesterol and inflammation and indicate that decreasing LDL levels is one of the key goals for improving cardiovascular outcome.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Complement activation by cholesterol crystals triggers a subsequent cytokine response

In the host a diverse collection of endogenous danger signals is constantly generated consisting of waste material as protein aggregates or crystalline materials that are recognized and handled by soluble pattern recognition receptors and phagocytic cells of the innate immune system. These signals may under certain circumstances drive processes leading to adverse inflammation. One example is cholesterol crystals (CC) that accumulate in the vessel wall during early phases of atherogenesis and represent an important endogenous danger signal promoting inflammation. CC is recognized by the lectin- and classical pathways of the complement system resulting in activation of C3 and C5 with release of inflammatory mediators like the potent C5a fragment. Complement activation by CC leads to crosstalk with the NLRP3 inflammasome-caspase-1 pathway and production of IL-1β. Neutralization of IL-1β may have beneficial effects on atherosclerosis and a large clinical trial with an IL-1β inhibitor is currently in progress (the CANTOS study). However, upstream inhibition of CC-induced inflammation by using a complement inhibitor may be more efficient in treating atherosclerosis since this will block initiation of inflammation processes before downstream release of cytokines including IL-1β. Another therapeutic candidate can be broad-acting 2-hydroxypropyl-β-cyclodextrin, a compound that targets several mechanisms such as cholesterol efflux, complement gene expression, and the NLRP3 pathway. In summary, emerging evidence show that complement is a key upstream player in the pathophysiology of atherosclerosis and that therapy aiming at inhibiting complement could be effective in controlling atherosclerosis.

Intraplaque Expression of C-Reactive Protein Predicts Cardiovascular Events in Patients with Severe Atherosclerotic Carotid Artery Stenosis

Serum c-reactive protein (CRP) was suggested for the assessment of intermediate cardiovascular (CV) risk. Here, systemic or intraplaque CRP levels were investigated as predictors of major adverse cardiovascular events (MACEs) in patients with severe carotid stenosis. CRP levels were assessed in the serum and within different portions (upstream and downstream) of carotid plaques of 217 patients undergoing endarterectomy. The association between CRP and intraplaque lipids, collagen, neutrophils, smooth muscle cells (SMC), and macrophage subsets was determined. No correlation between serum CRP and intraplaque biomarkers was observed. In upstream portions, CRP content was directly correlated with intraplaque neutrophils, total macrophages, and M1 macrophages and inversely correlated with SMC content. In downstream portions, intraplaque CRP correlated with M1 and M2 macrophages. According to the cut-off point (CRP > 2.9%) identified by ROC analysis in upstream portions, Kaplan-Meier analysis showed that patients with high CRP levels had a greater rate of MACEs. This risk of MACEs increased independently of age, male gender, serum CRP, and statin use. In conclusion, in patients with severe carotid artery stenosis, high CRP levels within upstream portions of carotid plaques directly and positively correlate with intraplaque inflammatory cells and predict MACEs at an 18-month follow-up period.

C‑reactive protein/oxidized low density lipoprotein/β2‑glycoprotein i complexes induce lipid accumulation and inflammatory reaction in macrophages via p38/mitogen‑activated protein kinase and nuclear factor‑κB signaling pathways

Oxidized low-density lipoprotein (oxLDL) can bind to β2-glycoprotein I (β2GPI) and C-reactive protein (CRP) to form stable complexes, which exert certain effects in diabetic cardiovascular disease. A previous study by our group has confirmed that the resulting complexes promote atherosclerosis in diabetic BALB/c mice. The present study was designed to investigate the effects and potential mechanisms of oxLDL complexes on lipid accumulation and inflammatory reactions in RAW264.7 macrophages cultured in a hyperglycemic environment. Cultured cells were divided into seven groups, which were treated with phosphate‑buffered saline (control), CRP, β2GPI, oxLDL, CRP/oxLDL, oxLDL/β2GPI or CRP/oxLDL/β2GPI. The results revealed the formation of foam cells in the oxLDL, CRP/oxLDL, oxLDL/β2GPI as well as CRP/oxLDL/β2GPI groups. Compared with oxLDL, the three complexes induced less lipid accumulation (P<0.05) through inhibiting the expression of CD36 mRNA and promoting the expression of and ABCG1 mRNA (P<0.05 vs. oxLDL). Furthermore, the levels of inflammatory factors interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α were elevated in the CRP/oxLDL and CRP/oxLDL/β2GPI groups (P>0.05 vs. oxLDL), and obvious effects on p38/mitogen‑activated protein kinase and nuclear factor (NF)‑κB phosphorylation were also observed in these groups (P<0.05 vs. oxLDL). These results suggested that CRP/oxLDL/βG2P1 complexes may induce lipid accumulation and inflammation in macrophages via the p38/MAPK and NF‑κB signaling pathways. However, some differences were observed between the complexes, which may be attributed to the property of each constituent; therefore, further studies are required.

Plasma-derived Extracellular Vesicles Contain Predictive Biomarkers and Potential Therapeutic Targets for Myocardial Ischemic (MI) Injury

Myocardial infarction (MI) triggers a potent inflammatory response via the release of circulatory mediators, including extracellular vesicles (EVs) by damaged cardiac cells, necessary for myocardial healing. Timely repression of inflammatory response are critical to prevent and minimize cardiac tissue injuries, nonetheless, progression in this aspect remains challenging. The ability of EVs to trigger a functional response upon delivery of carried bioactive cargos, have made them clinically attractive diagnostic biomarkers and vectors for therapeutic interventions. Using label-free quantitative proteomics approach, we compared the protein cargo of plasma EVs between patients with MI and from patients with stable angina (NMI). We report, for the first time, the proteomics profiling on 252 EV proteins that were modulated with >1.2-fold after MI. We identified six up-regulated biomarkers with potential for clinical applications; these reflected post-infarct pathways of complement activation (Complement C1q subcomponent subunit A (C1QA), 3.23-fold change, p = 0.012; Complement C5 (C5), 1.27-fold change, p = 0.087), lipoprotein metabolism (Apoliporotein D (APOD), 1.86-fold change, p = 0.033; Apolipoprotein C-III (APOCC3), 2.63-fold change, p = 0.029) and platelet activation (Platelet glycoprotein Ib alpha chain (GP1BA), 9.18-fold change, p < 0.0001; Platelet basic protein (PPBP), 4.72-fold change, p = 0.027). The data have been deposited to the ProteomeXchange with identifier PXD002950. This novel biomarker panel was validated in 43 patients using antibody-based assays (C1QA (p = 0.005); C5 (p = 0.0047), APOD (p = 0.0267); APOC3 (p = 0.0064); GP1BA (p = 0.0031); PPBP (p = 0.0465)). We further present that EV-derived fibrinogen components were paradoxically down-regulated in MI, suggesting that a compensatory mechanism may suppress post-infarct coagulation pathways, indicating potential for therapeutic targeting of this mechanism in MI. Taken together, these data demonstrated that plasma EVs contain novel diagnostic biomarkers and therapeutic targets that can be further developed for clinical use to benefit patients with coronary artery diseases (CADs).

Complement and Cardiovascular Disease--The Missing Link in Haemodialysis Patients

BACKGROUND

Patients on haemodialysis (HD) have high rates of cardiovascular (CV) disease and activation of the complement system. Despite evidence in non-renal patients that these may be linked, this association has received little attention in HD patients to date. In the setting of a randomised controlled trial we evaluated the relationships between baseline complement levels and subsequent CV events and mortality, in addition to the effects of HD with a vitamin E (VE)-coated dialysis membrane on circulating complement levels.

METHODS

A total of 260 HD patients were randomised to dialysis with a VE-coated dialysis membrane or non-VE coated equivalent for 12 months. Blood samples were taken at baseline, 6 and 12 months for measurement of C3, factor D, factor H and SC5b-9 levels. Data were collected prospectively on deaths and CV events.

RESULTS

Higher C3 levels at baseline were associated with subsequent CV events (hazard ratio 1.20 (1.01-1.42) per 0.1 mg/ml). Patients with intermediate SC5b-9 levels had significantly lower CV event rates and mortality than those with either high or low levels (p < 0.01). There were no effects of the VE-membranes on the complement components measured nor the clinical endpoints considered.

CONCLUSIONS

The levels of C3 and SC5b-9 may have prognostic utility for predicting future CV events and/or mortality in HD patients - a relationship that requires further investigation. Dialysing prevalent HD patients with VE-bonded polysulfone membranes for a period of 12 months did not alter the circulating levels of the alternative complement pathway components considered here.

Interplay between CRP, Atherogenic LDL, and LOX-1 and Its Potential Role in the Pathogenesis of Atherosclerosis

BACKGROUND

Studies have shown that the classic acute-phase protein C-reactive protein (CRP) has proinflammatory effects on vascular cells and may play a causal role in the pathogenesis of coronary artery disease. A growing body of evidence has suggested that interplay between CRP, lectin-like oxidized LDL receptor-1 (LOX-1), and atherogenic LDL may underlie the mechanism of endothelial dysfunction that leads to atherosclerosis.

CONTENT

We review the biochemical evidence for an association of CRP, LOX-1, and either oxidized LDL (OxLDL) or electronegative L5 LDL with the pathogenesis of coronary artery disease. Artificially oxidized OxLDL has been studied extensively for its role in atherogenesis, as has electronegative L5 LDL, which is present at increased levels in patients with increased cardiovascular risks. OxLDL and L5 have been shown to stimulate human aortic endothelial cells to produce CRP, indicating that CRP is synthesized locally in the endothelium. The ligand-binding face (B-face) of CRP has been shown to bind the LOX-1 scavenger receptor and increase LOX-1 expression in endothelial cells, thereby promoting the uptake of OxLDL or L5 by LOX-1 into endothelial cells to induce endothelial dysfunction.

SUMMARY

CRP and LOX-1 may form a positive feedback loop with OxLDL or L5 in atherogenesis, whereby increased levels of atherogenic LDL in patients with cardiovascular risks induce endothelial cells to express CRP, which may in turn increase the expression of LOX-1 to promote the uptake of atherogenic LDL into endothelial cells. Further research is needed to confirm a causal role for CRP in atherogenesis.

Reconstituted High-Density Lipoprotein Attenuates Cholesterol Crystal-Induced Inflammatory Responses by Reducing Complement Activation

Chronic inflammation of the arterial wall is a key element in the development of atherosclerosis, and cholesterol crystals (CC) that accumulate in plaques are associated with initiation and progression of the disease. We recently revealed a link between the complement system and CC-induced inflammasome caspase-1 activation, showing that the complement system is a key trigger in CC-induced inflammation. HDL exhibits cardioprotective and anti-inflammatory properties thought to explain its inverse correlation to cardiovascular risk. In this study, we sought to determine the effect of reconstituted HDL (rHDL) on CC-induced inflammation in a human whole blood model. rHDL bound to CC and inhibited the CC-induced complement activation as measured by soluble terminal C5b-9 formation and C3c deposition on the CC surface. rHDL attenuated the amount of CC-induced complement receptor 3 (CD11b/CD18) expression on monocytes and granulocytes, as well as reactive oxygen species generation. Moreover, addition of CC to whole blood resulted in release of proinflammatory cytokines that were inhibited by rHDL. Our results support and extend the notion that CC are potent triggers of inflammation, and that rHDL may have a beneficial role in controlling the CC-induced inflammatory responses by inhibiting complement deposition on the crystals.

Inflammaging in skin and other tissues - the roles of complement system and macrophage

Inflammaging refers to a continuous, low-grade inflammation associated with aging. Such chronic inflammatory response could build up with time and gradually causes tissue damage. It is considered as one of the driving forces for many age-related diseases such as diabetes, atherosclerosis, age-related macular degeneration (AMD), and skin aging. There is mounting evidence that indicates aging is driven by the pro-inflammatory cytokines and substances produced by our body’s innate immune system. The macrophage and complement system, two important components of innate immune system, have attracted more and more attention since they appear to be involved in the pathogenesis of several inflammaging-associated diseases, such as AMD and atherosclerosis. This paper will review what we know about these two innate immune systems in the pathogenesis of AMD, atherosclerosis and skin aging.

Bacteria present in carotid arterial plaques are found as biofilm deposits which may contribute to enhanced risk of plaque rupture

Atherosclerosis, a disease condition resulting from the buildup of fatty plaque deposits within arterial walls, is the major underlying cause of ischemia (restriction of the blood), leading to obstruction of peripheral arteries, congestive heart failure, heart attack, and stroke in humans. Emerging research indicates that factors including inflammation and infection may play a key role in the progression of atherosclerosis. In the current work, atherosclerotic carotid artery explants from 15 patients were all shown to test positive for the presence of eubacterial 16S rRNA genes. Density gradient gel electrophoresis of 5 of these samples revealed that each contained 10 or more distinct 16S rRNA gene sequences. Direct microscopic observation of transverse sections from 5 diseased carotid arteries analyzed with a eubacterium-specific peptide nucleic acid probe revealed these to have formed biofilm deposits, with from 1 to 6 deposits per thin section of plaque analyzed. A majority, 93%, of deposits was located proximal to the internal elastic lamina and associated with fibrous tissue. In 6 of the 15 plaques analyzed, 16S rRNA genes from Pseudomonas spp. were detected. Pseudomonas aeruginosa biofilms have been shown in our lab to undergo a dispersion response when challenged with free iron in vitro. Iron is known to be released into the blood by transferrin following interaction with catecholamine hormones, such as norepinephrine. Experiments performed in vitro showed that addition of physiologically relevant levels of norepinephrine induced dispersion of P. aeruginosa biofilms when grown under low iron conditions in the presence but not in the absence of physiological levels of transferrin.

IMPORTANCE

The association of bacteria with atherosclerosis has been only superficially studied, with little attention focused on the potential of bacteria to form biofilms within arterial plaques. In the current work, we show that bacteria form biofilm deposits within carotid arterial plaques, and we demonstrate that one species we have identified in plaques can be stimulated in vitro to undergo a biofilm dispersion response when challenged with physiologically relevant levels of norepinephrine in the presence of transferrin. Biofilm dispersion is characterized by the release of bacterial enzymes into the surroundings of biofilm microcolonies, allowing bacteria to escape the biofilm matrix. We believe these enzymes may have the potential to damage surrounding tissues and facilitate plaque rupture if norepinephrine is able to stimulate biofilm dispersion in vivo. This research, therefore, suggests a potential mechanistic link between hormonal state and the potential for heart attack and stroke.

Recognition functions of pentameric C-reactive protein in cardiovascular disease

C-reactive protein (CRP) performs two recognition functions that are relevant to cardiovascular disease. First, in its native pentameric conformation, CRP recognizes molecules and cells with exposed phosphocholine (PCh) groups, such as microbial pathogens and damaged cells. PCh-containing ligand-bound CRP activates the complement system to destroy the ligand. Thus, the PCh-binding function of CRP is defensive if it occurs on foreign pathogens because it results in the killing of the pathogen via complement activation. On the other hand, the PCh-binding function of CRP is detrimental if it occurs on injured host cells because it causes more damage to the tissue via complement activation; this is how CRP worsens acute myocardial infarction and ischemia/reperfusion injury. Second, in its nonnative pentameric conformation, CRP also recognizes atherogenic low-density lipoprotein (LDL). Recent data suggest that the LDL-binding function of CRP is beneficial because it prevents formation of macrophage foam cells, attenuates inflammatory effects of LDL, inhibits LDL oxidation, and reduces proatherogenic effects of macrophages, raising the possibility that nonnative CRP may show atheroprotective effects in experimental animals. In conclusion, temporarily inhibiting the PCh-binding function of CRP along with facilitating localized presence of nonnative pentameric CRP could be a promising approach to treat atherosclerosis and myocardial infarction. There is no need to stop the biosynthesis of CRP.

Inhibiting C-reactive protein for the treatment of cardiovascular disease: promising evidence from rodent models

Raised blood C-reactive protein (CRP) level is a predictor of cardiovascular events, but whether blood CRP is causal in the disease process is unknown. The latter would best be defined by pharmacological inhibition of the protein in the context of a randomized case-control study. However, no CRP specific drug is currently available so such a prospective study cannot be performed. Blood CRP is synthesized primarily in the liver and the liver is an organ where antisense oligonucleotide (ASO) drugs accumulate. Taking advantage of this we evaluated the efficacy of CRP specific ASOs in rodents with experimentally induced cardiovascular damage. Treating rats for 4 weeks with a rat CRP-specific ASO achieved >60% reduction of blood CRP. Notably, this effect was associated with improved heart function and pathology following myocardial infarction (induced by ligation of the left anterior descending artery). Likewise in human CRP transgenic mice treated for 2 weeks with a human CRP-specific ASO, blood human CRP was reduced by >70% and carotid artery patency was improved (2 weeks after surgical ligation). CRP specific ASOs might pave the way towards a placebo-controlled trial that could clarify the role of CRP in cardiovascular disease.

Interpretation of C-reactive protein concentrations in critically ill patients

Infection is often difficult to recognize in critically ill patients because of the marked coexisting inflammatory process. Lack of early recognition prevents timely resuscitation and effective antimicrobial therapy, resulting in increased morbidity and mortality. Measurement of a biomarker, such as C-reactive protein (CRP) concentration, in addition to history and physical signs, could facilitate diagnosis. Although frequently measured in clinical practice, few studies have reported on the pathophysiological role of this biomarker and its predictive value in critically ill patients. In this review, we discuss the pathophysiological role of CRP and its potential interpretation in the inflammatory processes observed in critically ill patients.

Endothelial nitric oxide synthase phosphorylation at Threonine 495 and mitochondrial reactive oxygen species formation in response to a high H₂O₂ concentration

BACKGROUND

Hydrogen peroxide (H₂O₂) is produced in vessels during ischemia/reperfusion and during inflammation, both leading to vascular dysfunction. We investigated cellular pathways involved in endothelial nitric oxide synthase (eNOS) phosphorylation at Threonine 495 (Thr(495)) in human umbilical vein endothelial cells (HUVECs) exposed to H₂O₂.

METHODS

HUVECs were exposed to 400 μM H₂O₂ for 30 min. Phosphorylation at Thr(495) was assessed by Western blotting and reactive oxygen species (ROS) monitored by flow cytometry. Protein kinase C (PKC) pathways were investigated by pretreatment with PKC-β inhibitor ruboxistaurin or pan-PKC inhibitor GF109203X. In addition, we investigated ROCK and ERK pathways by MEKK1/2 inhibitor U0126 and ROCK inhibitor Y27632.

RESULTS

H₂O₂ increased eNOS phosphorylation at Thr(495) (to 176% vs. control (100%), p < 0.001) along with increased mitochondrial ROS formation (from 19.7 to 45.3%, p < 0.01). This rise in phosphorylation could be prevented by U0126 and Y27632 in a dose-dependent manner, but did not result in lowered mitochondrial ROS formation. Conversely, addition of the antioxidant N-acetyl-L-cysteine only prevented mitochondrial ROS formation but did not prevent phosphorylation of eNOS Thr(495).

CONCLUSION

H₂O₂-mediated phosphorylation of eNOS Thr(495) is mediated by ROCK and ERK activity, but not by PKC, and is uncoupled from mitochondrial ROS signaling. Furthermore, ERK inhibition increased mitochondrial ROS formation.

Inflammatory biomarkers for predicting cardiovascular disease

The pathology of cardiovascular disease (CVD) is complex; multiple biological pathways have been implicated, including, but not limited to, inflammation and oxidative stress. Biomarkers of inflammation and oxidative stress may serve to help identify patients at risk for CVD, to monitor the efficacy of treatments, and to develop new pharmacological tools. However, due to the complexities of CVD pathogenesis there is no single biomarker available to estimate absolute risk of future cardiovascular events. Furthermore, not all biomarkers are equal; the functions of many biomarkers overlap, some offer better prognostic information than others, and some are better suited to identify/predict the pathogenesis of particular cardiovascular events. The identification of the most appropriate set of biomarkers can provide a detailed picture of the specific nature of the cardiovascular event. The following review provides an overview of existing and emerging inflammatory biomarkers, pro-inflammatory cytokines, anti-inflammatory cytokines, chemokines, oxidative stress biomarkers, and antioxidant biomarkers. The functions of each biomarker are discussed, and prognostic data are provided where available.

Soluble form of membrane attack complex independently predicts mortality and cardiovascular events in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention

BACKGROUND

The complement system is an important mediator of inflammation, which plays a pivotal role in atherosclerosis and acute myocardial infarction (AMI). Animal studies suggest that activation of the complement cascade resulting in the formation of soluble membrane attack complex (sMAC), contributes to both atherosclerosis and plaque rupture and may be the direct cause of tissue damage related to ischemia/reperfusion injury. However clinical data of sMAC during an AMI is sparse. Accordingly the aim was to investigate the prognostic role of sMAC in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS

We included 725 STEMI-patients admitted to a single, high-volume invasive heart centre, treated with primary percutaneous coronary intervention (PCI), from September 2006 to December 2008. Blood samples were drawn immediately before PCI. Plasma sMAC was measured using an in-house immunoassay. Endpoints were all-cause mortality (n = 62) and the combined endpoint (n = 122) of major cardiovascular events (MACE) defined as cardiovascular mortality and admission due recurrent AMI or heart failure. Follow-up time was 12 months.

RESULTS

During 12 months of follow-up 62 patients died from all causes and 122 patients reached the combined end-point of MACE. Patients with high sMAC (>75th percentile) had increased risk of both all-cause mortality and MACE. Even after adjustment for confounding risk factors by Cox-regression analyses, high levels of sMAC remained an independent predictor of all-cause mortality (hazard ratio 1.81 [95% CI 1.06-3.06; P = .029]) and MACE (hazard ratio 1.70 [95% CI 1.16-2.48; P = .006]).

CONCLUSIONS

High plasma sMAC independently predicts all-cause mortality and MACE in STEMI-patients treated with PCI.

The pro-atherogenic effects of macrophages are reduced upon formation of a complex between C-reactive protein and lysophosphatidylcholine

Rationale

C-reactive protein (CRP) and lysophosphatidylcholine (LPC) are phosphorylcholine-(PC)-containing oxidized phospholipids (oxPLs) found in oxidized LDL (oxLDL), which trigger pro-atherogenic activities of macrophages during the process of atherosclerosis. It has been previously reported that CRP binds to the PC head group of oxLDL in a calcium-dependent manner. The aim of this study was to investigate the importance of binding between CRP and LPC to the pro-atherogenic activities of macrophages.

Objectives and findings

A chemiluminescent immunoassay and HPLC showed that human recombinant CRP formed a stable complex with LPC in the presence of calcium. The Kd value of the binding of the CRP-LPC complex to the receptors FcγRIA or FcγRIIA was 3–5 fold lower than that of CRP alone. The CRP-LPC complex triggered less potent generation of reactive oxygen species and less activation of the transcription factors AP-1 and NF-kB by human monocyte-derived macrophages in comparison to CRP or LPC alone. However, CRP did not affect activities driven by components of oxLDL lacking PC, such as upregulation of PPRE, ABCA1, CD36 and PPARγ and the enhancement of cholesterol efflux by human macrophages. The presence of CRP inhibited the association of Dil-labelled oxLDL to human macrophages.

Conclusions

The formation of complexes between CRP and PC-containing oxPLs, such as LPC, suppresses the pro-atherogenic effects of CRP and LPC on macrophages. This effect may in part retard the progression of 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.

Membrane attack by complement: the assembly and biology of terminal complement complexes

Complement system activation plays an important role in both innate and acquired immunity. Activation of the complement and the subsequent formation of C5b-9 channels (the membrane attack complex) on the cell membranes lead to cell death. However, when the number of channels assembled on the surface of nucleated cells is limited, sublytic C5b-9 can induce cell cycle progression by activating signal transduction pathways and transcription factors and inhibiting apoptosis. This induction by C5b-9 is dependent upon the activation of the phosphatidylinositol 3-kinase/Akt/FOXO1 and ERK1 pathways in a Gi protein-dependent manner. C5b-9 induces sequential activation of CDK4 and CDK2, enabling the G1/S-phase transition and cellular proliferation. In addition, it induces RGC-32, a novel gene that plays a role in cell cycle activation by interacting with Akt and the cyclin B1-CDC2 complex. C5b-9 also inhibits apoptosis by inducing the phosphorylation of Bad and blocking the activation of FLIP, caspase-8, and Bid cleavage. Thus, sublytic C5b-9 plays an important role in cell activation, proliferation, and differentiation, thereby contributing to the maintenance of cell and tissue homeostasis.

Complement activation: an emerging player in the pathogenesis of cardiovascular disease

A wealth of evidence indicates a fundamental role for inflammation in the pathogenesis of cardiovascular disease (CVD), contributing to the development and progression of atherosclerotic lesion formation, plaque rupture, and thrombosis. An increasing body of evidence supports a functional role for complement activation in the pathogenesis of CVD through pleiotropic effects on endothelial and haematopoietic cell function and haemostasis. Prospective and case control studies have reported strong relationships between several complement components and cardiovascular outcomes, and in vitro studies and animal models support a functional effect. Complement activation, in particular, generation of C5a and C5b-9, influences many processes involved in the development and progression of atherosclerosis, including promotion of endothelial cell activation, leukocyte infiltration into the extracellular matrix, stimulation of cytokine release from vascular smooth muscle cells, and promotion of plaque rupture. Complement activation also influences thrombosis, involving components of the mannose-binding lectin pathway, and C5b-9 in particular, through activation of platelets, promotion of fibrin formation, and impairment of fibrinolysis. The participation of the complement system in inflammation and thrombosis is consistent with the physiological role of the complement system as a rapid effector system conferring protection following vessel injury. However, in the context of CVD, these same processes contribute to development of atherosclerosis, plaque rupture, and thrombosis.

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.

Susceptibility of LDL and its subfractions to glycation

PURPOSE OF REVIEW

To highlight the potential importance of glycation as an atherogenic modification of LDL, factors determining glycated apolipoprotein B in vivo and susceptibility of LDL to glycation in vitro. We also discuss the distribution of glycated apolipoprotein B across different LDL subfractions in healthy controls, patients with type 2 diabetes and metabolic syndrome.

RECENT FINDINGS

Small, dense LDL, which is known to be most closely associated with atherogenesis, is more preferentially glycated in vivo and more susceptible to glycation in vitro than more buoyant LDL. Glycation and oxidation of LDL appear to be intimately linked. In patients with type 2 diabetes, plasma glycated apolipoprotein B correlated with small, dense LDL apolipoprotein B, but not with HbA1c. Glycated apolipoprotein B is significantly lower in statin-treated type 2 diabetes compared with those not on statins.

SUMMARY

Glycation of LDL occurs chiefly because of the nonenzymatic reaction of glucose and its metabolites with the free amino groups of lysine of which apolipoprotein B is rich. Higher concentrations of glycated LDL are present in diabetes than in nondiabetic individuals and metabolic syndrome. Even in nondiabetic individuals, however, there is generally more circulating glycated LDL than oxidatively modified LDL. Probably, oxidation and glycation of LDL are partially interdependent and indisputably coexist, and both prevent LDL receptor-mediated uptake and promote macrophage scavenger receptor-mediated LDL uptake. The recognition that LDL glycation is at least as important as oxidation in atherogenesis may lead to improvements in our understanding of its mechanism and how to prevent it.

Anticomplement therapy

The complement system is an important part of innate immunity; however, as with other parts of the immune system, the complement system can become pathologically activated and create or worsen disease. Anticomplement reagents have been studied for several years, but only recently have they emerged as a viable therapeutic tool. Here, we describe the role of the complement system in a wide array of diseases, as well as the use of anticomplement therapy as treatment for these diseases in animal models and in human clinical trials. Specifically, we will discuss the role of anticomplement therapy in paroxysmal nocturnal hemoglobinuria, glomerulonephritis, and heart disease, including coronary artery disease, myocardial infarction, and coronary revascularization procedures such as percutaneous coronary angioplasty and coronary artery bypass graft surgery.

Atherosclerosis-related functions of C-reactive protein

C-reactive protein (CRP) is secreted by hepatocytes as a pentameric molecule made up of identical monomers, circulates in the plasma as pentamers, and localizes in atherosclerotic lesions. In some cases, localized CRP was detected by using monoclonal antibodies that did not react with native pentameric CRP but were specific for isolated monomeric CRP. It has been reported that, once CRP is bound to certain ligands, the pentameric structure of CRP is altered so that it can dissociate into monomers. Accordingly, the monomeric CRP found in atherosclerotic lesions may be a stationary, ligand-bound, by-product of a ligand-binding function of CRP. CRP binds to modified forms of low-density lipoprotein (LDL). The binding of CRP to oxidized LDL requires acidic pH conditions; the binding at physiological pH is controversial. The binding of CRP to enzymatically-modified LDL occurs at physiological pH; however, the binding is enhanced at acidic pH. Using enzymatically-modified LDL, CRP has been shown to prevent the formation of enzymatically-modified LDL-loaded macrophage foam cells. CRP is neither pro-atherogenic nor atheroprotective in ApoE⁻(/)⁻ and ApoB¹⁰⁰(/)¹⁰⁰Ldlr ⁻(/)⁻ murine models of atherosclerosis, except in one study where CRP was found to be slightly atheroprotective in ApoB¹⁰⁰(/)¹⁰⁰Ldlr ⁻(/)⁻ mice. The reasons for the ineffectiveness of human CRP in murine models of atherosclerosis are not defined. It is possible that an inflammatory environment, such as those characterized by acidic pH, is needed for efficient interaction between CRP and atherogenic LDL during the development of atherosclerosis and to observe the possible atheroprotective function of CRP in animal models.

Dose-dependent effect of rosuvastatin in the regulation of metalloproteinase expression

BACKGROUND

The importance of rosuvastatin at therapeutic dosage in regulating the release, activity, protein level, and expression of matrix metalloproteinases (MMP)-2 and MMP-9 was investigated.

METHODS

Human umbilical artery smooth muscle cells were stimulated, in vitro, in a serum-free medium with rosuvastatin at various concentrations (2, 4, 7, and 10 ng/mL, which correspond to the maximal plasma concentration observed in healthy men after a daily oral intake of 5, 10, 20, and 40 mg, respectively). The release of MMP-2 and MMP-9 in the conditioned medium was assessed by enzyme-linked immunosorbent assay and confirmed by Western blot, the activity and expression were determined by zymography and polymerase chain reaction, respectively.

RESULTS

Human umbilical artery smooth muscle cells stimulated with rosuvastatin at 7 and 10 ng/mL had a significant lower release, activity, protein level, and expression of MMP-2 and MMP-9, when compared with those stimulated at 2 and 4 ng/mL (MMP-2 =p < 0.0001 and p < 0.0001, respectively; MMP-9 =p < 0.0001 and p < 0.0001, respectively).

CONCLUSION

The effects of rosuvastatin in reducing MMP-2 and MMP-9, which might stabilize the atherosclerotic plaques, are dose-dependent.