Enzymatic Modification of Low-Density Lipoprotein in the Arterial Wall

OBJECTIVE

Functionally interactive proteases of the plasminogen/plasmin and the matrix metalloproteinase (MMP) system degrade and reorganize the extracellular matrix of the vessel wall in atherosclerosis. Here we investigated whether such proteases are able to confer atherogenic properties onto low density lipoprotein by nonoxidative modification.

METHODS AND RESULTS

Similar to the recently described enzymatically-modified low-density lipoprotein (E-LDL), native LDL exposed to plasmin or matrix MMP-2 or MMP-9 and cholesterylester-hydrolase (CEH) showed extensive deesterification, with ratios of free cholesterol to total cholesterol rising to 0.8 compared with 0.2 in native LDL. When the ratio exceeded 0.6, both plasmin/CEH-LDL and MMP/CEH-LDL fused into larger particles. In parallel, they gained C-reactive protein-dependent complement-activating capacity. E-LDL produced with any protease/CEH combination was efficiently taken up by human macrophages, whereby marked induction of MMP-2 expression by E-LDL was observed. These in vitro findings had their in vivo correlates: urokinase-type plasminogen activator, MMP-2, and MMP-9 were detectable in both early and advanced human atherosclerotic lesions in colocalization with E-LDL.

CONCLUSIONS

Plasmin and MMP-2/MMP-9 may not only be involved in remodeling of the extracellular matrix in progressing plaques, but they may also be involved in lipoprotein modification during genesis and progression of atherosclerotic lesions.

C-Reactive Protein Enhances LOX-1 Expression in Human Aortic Endothelial Cells

C-reactive protein (CRP), a characteristic inflammatory marker, is a powerful predictor of cardiovascular events. Recent data suggest that CRP may also promote atherogenesis through inducing endothelial dysfunction. Lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 (LOX-1) is a newly identified endothelial receptor for oxLDL that plays a pivotal role in oxLDL-induced endothelial dysfunction. Whether CRP may regulate endothelial LOX-1 and induce endothelial dysfunction through this receptor is unknown. In the present study, we studied the in vitro effect of CRP on LOX-1 expression in human aortic endothelial cells (HAECs) and the role of LOX-1 in CRP-induced human monocyte adhesion to endothelium and oxLDL uptake by endothelial cells. Incubation of HAECs with CRP enhanced, in a dose- and time-dependent manner, LOX-1 mRNA and protein levels. Induction of LOX-1 protein was already present at 5 μg/mL CRP and reached a maximum at 25 μg/mL. This effect was reduced by antibodies against CD32/CD64, endothelin-1 (ET-1) and interleukin-6 (IL-6). The extent of stimulation of LOX-1 achieved by CRP was comparable to that elicited by high glucose and IL-6 and remained unchanged in presence of these factors. Finally, CRP increased, through LOX-1, both human monocyte adhesion to endothelial cells and oxLDL uptake by these cells. We conclude that CRP enhances endothelial LOX-1 expression and propose a new mechanism by which CRP may promote endothelial dysfunction, that of inducing LOX-1.

Opposing effects of C-reactive protein isoforms on shear-induced neutrophil-platelet adhesion and neutrophil aggregation in whole blood

BACKGROUND

Plasma C-reactive protein (CRP) level is a powerful predictor of cardiovascular events. However, it is not known whether CRP could affect neutrophil-platelet adhesion and neutrophil aggregation, key events in acute coronary syndromes. Emerging in vitro evidence suggests that some bioactivities of CRP are expressed on loss of the pentameric symmetry, resulting in formation of modified or monomeric CRP (mCRP).

METHODS AND RESULTS

We studied the impact of human native CRP and bioengineered mCRP that cannot rearrange into the pentameric structure on the kinetics of neutrophil-platelet adhesion and neutrophil aggregation in whole blood subjected to shear (approximately 100 s(-1)) using real-time flow cytometry. Shear resulted in upregulation of platelet P-selectin expression, leading to platelet capture of neutrophils and subsequent neutrophil aggregation, which was dependent on P-selectin, L-selectin, and CD18. Native CRP at clinically relevant concentrations markedly attenuated these changes. The residual amount of neutrophil adhesion was blocked with anti-CD18 or anti-CD11b antibody. By contrast, mCRP concentration-dependently enhanced shear-induced platelet P-selectin expression and increased the rate and extent of formation of both neutrophil-platelet and neutrophil-neutrophil aggregates. Complete abrogation of platelet-neutrophil adhesion and neutrophil aggregation required both anti-P-selectin and anti-CD18 antibodies but not anti-L-selectin antibody. The CRP action was markedly inhibited by an anti-CD32 antibody, whereas the mCRP effects were significantly attenuated by an anti-CD16 antibody.

CONCLUSIONS

These results indicate that native CRP inhibits platelet activation and prevents platelet capture of neutrophils, whereas mCRP displays potent prothrombotic activities under low levels of shear. Thus, mCRP rather than native CRP may precipitate acute coronary syndromes.

C-reactive protein: from innocent bystander to pivotal mediator of atherosclerosis

There is compelling evidence that C-reactive protein is a sensitive marker for the development of cardiovascular disease in the general population. Recent studies suggest that C-reactive protein is not only a biomarker but also an active mediator in the pathogenesis of atherosclerosis. We review the evidence and suggest mechanisms by which C-reactive protein can damage arterial endothelium and promote the development of atherosclerotic lesions, including the effects of C-reactive protein on arterial endothelial activation, macrophage recruitment, and foam cell generation. The direct role of C-reactive protein in sustaining a proinflammatory and procoagulant milieu within the arterial neointima is emphasized. We also discuss the evidence that C-reactive protein can injure arterial endothelium. Finally, we review therapies that target C-reactive protein for primary prevention and for the treatment of atherosclerotic diseases.

Adiponectin, insulin resistance, and C-reactive protein in postpubertal Asian Indian adolescents

High-sensitivity C-reactive protein (hs-CRP) levels are closely associated with adiposity and predict coronary heart disease and type 2 diabetes mellitus. However, relationships of CRP to adiponectin and other markers of insulin resistance have been inadequately researched in children. We measured fasting serum levels of adiponectin, insulin, hs-CRP, and lipoproteins, and recorded the anthropometric profile and percentage of body fat (%BF; bioimpedance method) in 62 (36 normal weight, 26 overweight) healthy, urban, postpubertal Asian Indian males (aged 14 to 18 years). Serum levels of adiponectin were lower (P = not significant [NS]), whereas those of fasting insulin (P = .01) and hs-CRP (P = .02) were higher in overweight subjects. Adiponectin levels inversely correlated with body mass index (BMI; r = -0.26, P < .05), %BF (r = -0.24, P < .05), fasting insulin (r = -0.32, P < .05) and insulin resistance measured by the homeostasis model of assessment (HOMA-IR; r = -0.31, P < .05), but not with hs-CRP levels. Fasting insulin and hs-CRP levels correlated significantly with BMI, %BF, waist circumference (WC), waist-to-hip circumference ratio (W-HR), and triceps and subscapular skinfold thickness. The correlation of adiponectin with insulin sensitivity was independent of abdominal obesity, but became nonsignificant after controlling for BMI and %BF. Further, BMI was an independent predictor of adiponectin levels and the ratio of adiponectin and %BF was an independent predictor of fasting insulin levels. Although adiponectin levels did not correlate with hs-CRP levels, we observed dichotomous relationships of adiponectin and hs-CRP levels with generalized and abdominal obesity, respectively. We conclude that generalized obesity affects the adiponectin-insulin relationship in postpubertal Asian Indian males; however, the relationship of adiponectin with hs-CRP needs further evaluation.

The prototypic tissue pentraxin PTX3, in contrast to the short pentraxin serum amyloid P, inhibits phagocytosis of late apoptotic neutrophils by macrophages

OBJECTIVE

Phagocytosis of apoptotic cells can be facilitated by complement components and short pentraxins, such as serum amyloid P (SAP). In contrast, the long pentraxin PTX3 was shown to inhibit phagocytosis of apoptotic Jurkat cells by dendritic cells and to bind late apoptotic polymorphonuclear leukocytes (PMNs). Recently, levels of the pentraxin PTX3 were shown to parallel disease activity in small-vessel vasculitis, which is often characterized by leukocytoclasia, a persistence of leukocyte remnants in the vessel wall. We undertook this study to test our hypothesis that PTX3 inhibits phagocytosis of late apoptotic PMNs by macrophages, thereby leading to their accumulation in the vessel wall.

METHODS

Macrophages were allowed to phagocytose late apoptotic or secondary necrotic PMNs that were incubated with or without PTX3 for 30 minutes prior to phagocytosis. Phagocytosis was allowed to occur in the presence of 30% normal human serum with or without SAP and with or without depletion of complement. To discriminate between an inhibitory effect of PTX3 on binding and the internalization of apoptotic PMNs into macrophages, internalization was blocked by cytochalasin B.

RESULTS

SAP and complement were both necessary for effective in vitro phagocytosis. In contrast, PTX3 inhibited phagocytosis in a dose-dependent manner, from 11% inhibition at 6.25 microg/ml to almost complete inhibition at 100 microg/ml. Furthermore, PTX3 partly affected binding of apoptotic PMNs to macrophages.

CONCLUSION

PTX3, in contrast to SAP and complement, inhibits phagocytosis of late apoptotic PMNs by monocyte-derived macrophages in a dose-dependent manner. Therefore, PTX3 can play a role in the development of leukocytoclasia by affecting the clearance of apoptotic PMNs, thereby inducing their accumulation in the vessel wall.

Common ancestors: chronic progressive diseases have the same pathogenesis

In multiple organ systems, chronic progressive disease is characterized at the tissue level by increase in inflammatory cytokines, cell apoptosis and progressive fibrosis, suggesting a possible commonality of pathogenesis. This speculation is supported by the observation that elevated systemic levels of cytokines and/or CRP predict the appearance of disease, progression of disease, and disease complications. Some therapeutic interventions that reduce the expression of inflammatory cytokines, such as HMG Co-A reductase inhibitors, slow the progression of a number of chronic diseases, independent of their effect on cholesterol level. Taken together, these data suggest a unifying hypothesis for many chronic progressive diseases. Diverse noxious stimuli activate a normal protective inflammatory response. This response typically defervesces with elimination of the stimulus, reestablishing homeostasis. When homeostasis is not restored, that is, the inflammatory response persists, cell apoptosis and tissue fibrosis can result. The universality of this tissue response derives from the fact that all cells derive from the same blastocyst. Since cell differentiation results in different tissue functions, however, the clinical manifestations of disease are also vastly different, obscuring the underlying disease process. The relevance of this insight is that it provides a potential framework for testing old and new therapies which might inhibit a diverse set of clinical conditions at several levels of the disease process.

The chronic inflammatory hypothesis for the morbidity associated with morbid obesity: implications and effects of weight loss

BACKGROUND

Obesity is a worldwide pandemic that causes a multitude of co-morbid conditions.However, there has been slow progress in understanding the basic pathophysiology that underlies co-morbid conditions associated with obesity. Recently, there has been intense interest in the role of inflammation in obesity. Using the inflammatory hypothesis, many of the mechanisms by which co-morbid conditions are associated with obesity are being elucidated.

METHODS

We searched the literature and reviewed all relevant articles. We focused on hormones and cytokines that have been associated with other inflammatory conditions such as sepsis and systemic inflammatory response syndrome.

FINDINGS

Angiotensinogen (AGT), transforming growth factor beta (TGFbeta), tumor necrosis factor alpha (TNFalpha), and interleukin six (IL-6) are all elevated in obesity and correlate with several markers of adipocyte mass. These mediators have detrimental effects on hypertension, diabetes, dyslipidemia, thromboembolic phenomena, infections, and cancer. Weight loss results in a reduction of inflammatory mediators and a diminution of the associated co-morbid conditions.

CONCLUSIONS

The success of weight loss surgery in treating the complications associated with obesity is most probably related to the reduction of inflammatory mediators. While some aspects of bariatric physiology remain unclear, there appears to be a strong association between obesity and inflammation, thereby rendering obesity a chronic inflammatory state. A clearer understanding of the physiology of obesity will allow physicians who treat the obese to develop better strategies to promote weight loss and improve the well-being of millions of individuals.

[Vitamin D and survival of hemodialysis patients]

Vitamin D receptors are expressed not only in the classical target organs (bone, parathyroid glands, kidneys and intestine) but also in other non-classical targets including arteries, heart, immune system, endocrine organs, and nervous system. Therefore, the deficiency of active forms of vitamin D in uremia may explain various abnormalities in biological functions and survival disadvantage in this disease condition. Previous studies reported that treatment with vitamin D had beneficial effects on cardiac and immune functions in dialysis patients. A recent observational cohort study indicated that the mortality risk was different between the groups taking different types of vitamin D analogues. We found that patients on a low-dose oral alfacalcidol showed a significantly lower risk for cardiovascular death than those without vitamin D supplementation. Although these observations need further confirmation by randomized controlled studies, appropriate use of active forms of vitamin D may improve the outcomes of patients with chronic kidney disease.

Pathophysiology of coronary heart disease: a brief review

Coronary heart disease (CHD) remains a persistent public health burden in the United States, and it is the cause of one of every five deaths each year. The link between lipids and CHD has been firmly established, first by epidemiologic studies and, more recently, by long-term outcomes trials that demonstrated that lowering low-density lipoprotein cholesterol (LDL-C) levels significantly reduced the risk of major coronary events. Based on this evidence, the National Cholesterol Education Program recommends lowering the LDL-C level to reduce CHD risk, particularly for patients at highest risk. Recently, evidence has emerged that suggests that C-reactive protein may be a mediator of atherosclerosis and its presence may be indicative of increased risk of CHD. Although these data are intriguing, their relevance has yet to be established in prospective outcomes trials. Until then, lipid lowering through lifestyle modification and the use of safe and effective modes of therapy should be the emphasis of CHD risk reduction strategies.

Complement activation by necrotic cells in normal plasma environment compares to that by late apoptotic cells and involves predominantly IgM

Necrotic cells are generally considered to stimulate inflammation, whereas apoptotic cells should not. However, apoptotic cells have pro-inflammatory properties since they can activate complement. To what extent this activation compares to that by necrotic cells is not known. We compared complement activation by necrotic cells and apoptotic cells in plasma. Jurkat cells were made apoptotic or necrotic by incubation with etoposide or by heat shock, respectively. Cells incubated in recalcified plasma were tested for C3 and C4 fixation and fluid phase generation of complement activation products. Fixation of C3 and C4 to necrotic cells occurred mainly via the classical pathway, independent from the method of necrosis induction and the cell type. Depletion of IgM from plasma almost completely abrogated complement fixation by necrotic cells, which was restored by supplementation with purified IgM. Complement activation by late apoptotic cells was comparable to that by necrotic cells regarding the extent and dependence on IgM. Moreover, incubation of plasma with necrotic or late apoptotic cells led to the generation of comparable amounts of complement activation products. These results indicate that late apoptotic and necrotic cells employ similar complement activation mechanisms in the plasma environment.

C-reactive Protein

C-reactive protein (CRP) is a phylogenetically highly conserved plasma protein, with homologs in vertebrates and many invertebrates, that participates in the systemic response to inflammation. Its plasma concentration increases during inflammatory states, a characteristic that has long been employed for clinical purposes. CRP is a pattern recognition molecule, binding to specific molecular configurations that are typically exposed during cell death or found on the surfaces of pathogens. Its rapid increase in synthesis within hours after tissue injury or infection suggests that it contributes to host defense and that it is part of the innate immune response. Recently, an association between minor CRP elevation and future major cardiovascular events has been recognized, leading to the recommendation by the Centers for Disease Control and the American Heart Association that patients at intermediate risk of coronary heart disease might benefit from measurement of CRP. This review will largely focus on our current understanding of the structure of CRP, its ligands, the effector molecules with which it interacts, and its apparent functions.

Causes and therapy of microinflammation in renal failure

Microinflammation in renal failure has been the subject of numerous studies, but the causes of the inflammatory response in these patients are not clear. There are several potential causes and possible therapies for microinflammation, and they are discussed in this review with regard to uraemia and acidosis, heart failure and volume overload, oxidative stress and iron therapy, and bioincompatibility, especially regarding dialysis membranes. In addition, issues regarding dialysate contamination and access site infection are examined, followed by a discussion of possible drug therapy for microinflammation with angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists, statins, aspirin, and antioxidants, such as vitamin E.

C-reactive protein impairs angiogenic functions and decreases the secretion of arteriogenic chemo-cytokines in human endothelial progenitor cells

C-reactive protein (CRP), a predictor of future cardiovascular diseases, has been reported to damage the vascular wall by inducing endothelial dysfunction and inflammation. This proatherogenic CRP was speculated to have a role in attenuating angiogenic functions of human endothelial progenitor cells (EPCs), possibly impairing vascular regeneration and increasing cardiovascular vulnerability to ischemic injury. Herein, we investigated the direct effect of CRP on angiogenic activity and gene expression in human EPCs. Incubation of EPCs with human recombinant CRP significantly inhibited EPC migration in response to vascular endothelial growth factor, possibly by decreasing the expression of endothelial nitric oxide synthase and subsequent nitric oxide production. In addition, CRP-treated EPCs showed the reduced adhesiveness onto an endothelial cell monolayer. When assayed for the gene expression of arteriogenic chemo-cytokines, CRP substantially decreased their expression levels in EPC, in part due to the upregulation of suppressors of cytokine signaling proteins. These results suggest that CRP directly attenuates the angiogenic and possibly arteriogenic functions of EPCs. This CRP-induced EPC dysfunction may impair the vascular regenerative capacity of EPCs, thereby leading to increased risk of cardiovascular diseases.

The role of C-reactive protein in ischemia/reperfusion injury and preconditioning in a rat model of myocardial infarction

For the first time the involvement of C-Reactive protein (CRP) in early (acute) and delayed ischemic (IPC) and pharmacological (chemical) preconditioning (CPC) in an in vivo model of rat myocardial infarction was presented. Acute IPC was produced by three 5 minute occlusion (ischemia) periods interspersed with 5 minute reperfusion, followed by 30 minute occlusion of the left coronary artery and 2 hour reperfusion injury. Acute CPC was produced by a k-opioid receptor agonist U50488H (5 mg/kg) applied i.v. 15 minutes before 30 minute ischemia/ 2 hour reperfusion. Delayed preconditioning was produced by 30 minute ischemia/ 2 hour reperfusion, induced 24 hour after either ischemic or pharmacological preconditioning. The myocardial ischemia/reperfusion injury was evaluated on the basis of total and cardiac creatine kinase isoenzyme activity, functional recovery of the heart (ECG), infarct size (% IS/RA) and mortality at the end of the experiments. The results obtained showed that: k-opioid receptor agonist U50488H mimics both the acute and delayed IPC in the above experimental protocol; Both acute IPC and most probably CPC act by opening of K(ATP) channels (the effects were blocked by nonspecific ATP-sensitive K channel blocker glybenclamide), and via activation of protein kinase C (a selective protein kinase C inhibitor chelerythrine blocked the efects); C-reactive protein (CRP) was significantly elevated by 54% in non-preconditioned acute ischemia/reperfusion injury. The elevation was more pronounced (82% increase) 24 hour after non-preconditioned ischemia/reperfusion injury. It reflected very well the increase in cardiac isoenzymes, infarct size and mortality of the rats, and can be used as a marker of the severity of myocardial injury in this model; The increase of CRP was prevented by both IPC and CPC in early, and especially in late preconditioning. This confirms the involvement of CRP as a marker in cardiac ischemic/reperfusion injury. It was concluded that in addition to the established involvement of adenosine, bradykinin, opioid and other receptors, a suppression of myocardial CRP/complement production might be involved in the biological mechanism of preconditioning. This could be a promising perspective in clinical interventions against ischemia/reperfusion injuries of the heart.

Inflammation in atherothrombotic disease

Atherosclerosis is a systemic disease in which vascular inflammation plays a key role. Indeed, inflammation is closely linked to atherosclerotic disease at all stages, from silent progression to clinical manifestations. There is now strong epidemiologic evidence that mediators of inflammation, like C-reactive protein, predict cardiovascular risk independently of "classical" risk factors. Consequently, new disease-modifying drugs targeting inflammation are under investigation and may change the approach to treatment of atherosclerosis in the near future.

C-Reactive Protein: Risk Marker or Mediator in Atherothrombosis?

Inflammation appears to be pivotal in all phases of atherosclerosis from the fatty streak lesion to acute coronary syndromes. An important downstream marker of inflammation is C-reactive protein (CRP). Numerous studies have shown that CRP levels predict cardiovascular disease in apparently healthy individuals. This has resulted in a position statement recommending cutoff levels of CRP <1.0, 1.0 to 3.0, and >3.0 mg/L equating to low, average, and high risk for subsequent cardiovascular disease. More interestingly, much in vitro data have now emerged in support of a role for CRP in atherogenesis. To date, studies largely in endothelial cells, but also in monocyte-macrophages and vascular smooth muscle cells, support a role for CRP in atherogenesis. The proinflammatory, proatherogenic effects of CRP that have been documented in endothelial cells include the following: decreased nitric oxide and prostacyclin and increased endothelin-1, cell adhesion molecules, monocyte chemoattractant protein-1 and interleukin-8, and increased plasminogen activator inhibitor-1. In monocyte-macrophages, CRP induces tissue factor secretion, increases reactive oxygen species and proinflammatory cytokine release, promotes monocyte chemotaxis and adhesion, and increases oxidized low-density lipoprotein uptake. Also, CRP has been shown in vascular smooth muscle cells to increase inducible nitric oxide production, increase NFκb and mitogen-activated protein kinase activities, and, most importantly, upregulate angiotensin type-1 receptor resulting in increased reactive oxygen species and vascular smooth muscle cell proliferation. Future studies should be directed at delineating the molecular mechanisms for these important in vitro observations. Also, studies should be directed at confirming these findings in animal models and other systems as proof of concept. In conclusion, CRP is a risk marker for cardiovascular disease and, based on future studies, could emerge as a mediator in atherogenesis.

Inflammation and endothelial dysfunction: intimate companions in the pathogenesis of vascular disease?

There is increasing evidence to implicate inflammation as an important precursor of endothelial dysfunction. This mechanistic link is apparent across the entire spectrum of inflammatory status, i.e. endothelial function is apparent following acute infection, and in subjects with chronic high-grade inflammation and, perhaps most importantly, persistent low-grade inflammation. The recognition of this relationship has present therapeutic ramifications, but also requires that future longitudinal studies determining the predictive ability of endothelial function measures for vascular events should incorporate markers of inflammation as potential confounders. In this issue of Clinical Science, Fichtlscherer and co-workers describe a link between endothelial function and sPLA(2) (secretory non-pancreatic type II phospholipase A(2)) serum activity.

CRP as a mediator of disease

Of the various hypotheses offered to explain atherosclerosis, inflammation now appears to provide a key to this pathological process. Inflammation has been shown to play a major role in precipitating a cascade of events from formation of the atheromatous lesion in response to vascular injury through lipid ingestion by macrophages, to subsequent rupture of the lesion, and myocardial infarction. Atherosclerosis shares many inflammatory features with rheumatoid arthritis (RA), an autoimmune disease, and drugs that block the inflammatory cytokine pathway now provide effective treatment for RA. In animal models, blockers of the inflammatory cytokine pathway appear to block mononuclear cell binding to arterial plaque. C-reactive protein (CRP), an inflammatory marker, may also play a proinflammatory role in activating monocyte chemotactic protein. Antiatherosclerotic drugs may be exerting some of their beneficial effects by inhibiting the harmful effects of CRP.

Laboratory tests in diagnosis and management of diabetes mellitus. Practical considerations

The clinical laboratory plays an essential role in both the diagnosis and therapeutic monitoring of diabetes mellitus. Here, a short review of the main laboratory parameters used in the monitoring of diabetes--glucose (including point-of-care testing), HbA1c and microalbuminuria--is presented. The impact of pre-analytical and analytical performance criteria on the clinical decision making process is discussed.

C-Reactive Protein Does Not Directly Induce Tissue Factor in Human Monocytes

OBJECTIVE

It is generally assumed that C-reactive protein (CRP) induces synthesis of tissue factor (TF) in monocytic cells, thereby potentially initiating intravascular blood coagulation. We aimed to elucidate the mechanism of CRP-induced TF expression in monocytes and monocyte-derived macrophages (MDMs) in vitro.

METHODS AND RESULTS

Monocytes were isolated from the blood of healthy donors and cultured with or without CRP or lipopolysaccharide (LPS) to study the time course of TF antigen and TF mRNA expression. Addition of 100 microg/mL CRP did not result in a significant increase in TF antigen (range: 9 to 163 pg/10(6) cells, n=11) and TF mRNA (relative number of TF transcripts; N(TF)=0.01 to 0.33), when compared with nonstimulated cells (TF antigen 7 to 46 pg/10(6) cells, N(TF)=0.01 to 0.13). Variation of CRP concentration and exposure time did not affect the TF response. Similar results were obtained in monocytes cultured in suspension and in MDMs. In contrast, TF was strongly induced by 10 microg/mL LPS (TF antigen 1125 to 6120 pg/10(6) cells, N(TF)=5.94 to 23.43). Cultured monocytes did express FcRgammaII, a putative CRP receptor, and addition of CRP induced a 7-fold increase in the production of monocyte chemoattractant protein-1 (MCP-1). Interestingly, CRP addition to peripheral blood mononuclear cells (PBMCs) did result in TF expression on monocytic cells.

CONCLUSIONS

The absence of TF induction after incubation of purified monocytes with CRP indicates that CRP is unable to induce TF expression in monocytes and MDMs directly. The presence of CRP-induced TF expression in PBMCs suggests that CRP can induce TF indirectly, probably through cross-talk between cells.

Mechanistic Insights and Clinical Relevance of the Interaction between Acute Coronary Syndromes and Lipid Metabolism

As part of the acute phase reaction, lipid metabolism is significantly altered in patients with unstable coronary syndromes. The clinical relevance and the mechanisms underlying this phenomenon are discussed in this article. Cholesterol reduction takes place in the first hours of an acute coronary event; thus, plasma levels determined at this point should be interpreted with caution. This reduction may be just a consequence of the inflammatory response, or it may be also related to an increase in cellular uptake of cholesterol for tissue repair and hormonal synthesis. A synergistic effect between this predisposition to cholesterol reduction and statin therapy appears to exist during acute coronary syndromes. Triglyceride changes are variable during acute coronary syndromes, and recent data indicate that the pattern of triglyceride variation is a potential risk marker in those patients, possibly because it reflects neurohumoral changes related to the acute phase.

Possible Protective Role for C-Reactive Protein in Atherogenesis

Background— Previous work indicated that enzymatically remodeled LDL (E-LDL) might activate complement in atherosclerotic lesions via a C-reactive protein (CRP)–dependent and CRP-independent pathway. We sought to substantiate this contention and determine whether both pathways drive the sequence to completion.

Methods and Results— E-LDL was prepared by sequential treatment of LDL with a protease and cholesteryl esterase. Trypsin, proteinase K, cathepsin H, or plasmin was used with similar results. Functional tests were used to assess total complement hemolytic activity, and immunoassays were used to demonstrate C3 cleavage and to quantify C3a, C4a, C5a, and C5b-9. E-LDL preparations activated complement to completion, independent of CRP, when present above a threshold concentration (100 to 200 μg/mL in 5% serum). Below the threshold, all E-LDL preparations activated complement in dependence of CRP, but the pathway then halted before the terminal sequence. Native LDL and oxidized LDL did not activate complement under any circumstances tested. Immunohistological analyses corroborated the concept that CRP-dependent complement activation inefficiently generates C5b-9.

Conclusions— Binding of CRP to E-LDL is the first trigger for complement activation in the atherosclerotic lesion, but the terminal sequence is thereby spared. This putatively protective function of CRP is overrun at higher E-LDL concentrations, so that potentially harmful C5b-9 complexes are generated.

C-Reactive Protein Modifies the Relationship Between Blood Pressure and Microalbuminuria

C-reactive protein (CRP) and microalbuminuria reflect intimately related components of the atherosclerotic disease process. Epidemiological studies found only modest associations between CRP and microalbuminuria. Blood pressure, one of the components of the metabolic syndrome in the general population, is the main determinant of microalbuminuria in diabetes and hypertension. We questioned whether CRP modifies the relationship of blood pressure and other cardiovascular risk factors with microalbuminuria in a cross-sectional study in 8592 inhabitants from Groningen, The Netherlands. The crude data showed an increase in the prevalence of microalbuminuria with increasing CRP quartiles (4.8, 9.6, 14.5, and 18.6%, P<0.0001). On stratification for cardiovascular risk factors, the data revealed a significant and positive interaction between mean arterial pressure (MAP) and quartiles of CRP with respect to the risk of microalbuminuria (Wald statistic 9.2, P=0.03). In subjects with a MAP <90 mm Hg, a nonsignificant trend in the association between CRP quartiles and microalbuminuria was found (prevalence: 3.9%, 5.8%, 6.6%, 8.7%; P=0.11). This trend was much steeper and significant in subjects with an MAP >90 mm Hg (prevalence: 6.7%, 13.6%, 20.4%, 25.1%; P<0.0001). Controlling for other risk factors in multivariate analyses, the positive interaction persisted (P=0.0004). No significant interactions between other risk factors and CRP with respect to the risk of microalbuminuria were encountered. Thus, CRP modifies the relation between blood pressure and microalbuminuria.

Evidence for C-Reactive Protein's Role in (CRP) Vascular Disease: Atherothrombosis, Immuno-Regulation and CRP

For clinicians plasma C-reactive protein (CRP) levels are the only widely available tests that provide a tangible link between inflammation and atherosclerosis. New AHA/CDC joint guidelines from 2002-03 now include the measurement of CRP as a class IIa recommendation for stratifying patients with known cardiovascular disease (CVD) at a moderate (10-20%) 10-year event risk and a class IIb recommendation for patients without known CVD [1]. While the association of CRP and atherosclerosis is by now accepted, the molecular biology behind the association is evolving rapidly into a fascinating story. While some of the story remains obscure, this review aims to bridge the clinical and basic science and identify what is known about the role of this ancient molecule in atherosclerosis. The review covers CRP's interaction with atherosclerosis' major ingredients and cell types including the endothelium, monocytes and neutrophils, lipoproteins and the complement system. Taken together, the clinical and basic science leave the tantalizing impression that CRP has a fundamental role in atherogenesis, and hint at a more complex immunomodulatory effect which transforms the acute inflammatory response to vascular injury into the chronic inflammation seen in atherosclerosis.

Inflammation and atherosclerosis: role of C-reactive protein in risk assessment

Inflammation participates critically in atherosclerosis. Circulating levels of several inflammatory markers rise in individuals at risk for atherosclerotic events. In particular, elevation of plasma C-reactive protein (CRP), a nonspecific acute-phase reactant that is easily and reliably measured, has strong predictive power for cardiovascular events. Indeed, measurements of high-sensitivity CRP (hs-CRP) plasma levels add to both the prognostic information gleaned from assay of plasma lipid risk factors and the risk levels estimated by means of Framingham study-based criteria. Retrospective data suggest the hypothesis that hs-CRP plasma levels may be useful for guiding use of lipid-lowering therapy in individuals who appear to be at low risk according to traditional risk assessment. A large-scale, randomized clinical trial-Justification for the Use of Statins in Primary Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER)-will test whether rosuvastatin therapy will reduce incident cardiovascular disease in subjects with elevated plasma hs-CRP concentrations who do not meet current criteria for initiation of lipid-lowering drug therapy. Such clinical trial data may provide an evidence base for the use of plasma CRP assay as an adjuvant guide to therapy to complement the established traditional risk factors such as plasma lipid levels. Thus, medical practitioners are ushering in an era in which the biology of inflammation in atherosclerosis will find its way into clinical application.

Selective recognition of fibroblast growth factor-2 by the long pentraxin PTX3 inhibits angiogenesis

The long pentraxin PTX3 is a soluble pattern recognition receptor produced by monocytes and endothelial cells that plays a nonredundant role in inflammation. Several pathologic conditions are characterized by local production of both PTX3 and the angiogenic fibroblast growth factor-2 (FGF2). Here, solid-phase binding assays demonstrated that PTX3 binds with high affinity to FGF2 but not to a panel of cytokines and growth factors, including FGF1, FGF4, and FGF8. Accordingly, PTX3 prevented (125)I-FGF2 binding to endothelial cell receptors, leading to specific inhibition of FGF2-induced proliferation. PTX3 hampered also the motogenic activity exerted by endogenous FGF2 on a wounded endothelial cell monolayer. Moreover, PTX3 cDNA transduction in FGF2-transformed endothelial cells inhibited their autocrine FGF2-dependent proliferation and morphogenesis in vitro and their capacity to generate vascular lesions when injected in nude mice. Finally, PTX3 suppressed neovascularization triggered by FGF2 in the chick embryo chorioallantoic membrane with no effect on physiologic angiogenesis. In contrast, the short pentraxin C-reactive protein was a poor FGF2 ligand/antagonist. These results establish the selective binding of a member of the pentraxin superfamily to a growth factor. PTX3/FGF2 interaction may modulate angiogenesis in various physiopathologic conditions driven by inflammation, innate immunity, and/or neoplastic transformation.

Role of C-reactive protein in cardiovascular disease

OBJECTIVE

To discuss the role of C-reactive protein (CRP) in cardiovascular disease as a predictor of vascular events and identify key factors that increase or decrease this inflammatory marker.

DATA SOURCES

Articles were identified through searches of MEDLINE (1966-July 2003), International Pharmaceutical Abstracts (1970-June 2003), and bibliographies of selected articles. Search terms included C-reactive protein, HMG-CoA reductase inhibitors, fenofibrate, niacin, aspirin, estrogen, thiazolidinediones, and raloxifene. data selection and data extraction: All studies relevant to CRP and cardiovascular disease or the effects of pharmacologic and nonpharmacologic interventions on CRP levels were evaluated. All information deemed relevant to this review was included.

DATA SYNTHESIS

Numerous studies have shown a strong association between CRP levels and future vascular events (i.e., coronary, cerebrovascular, peripheral vascular disease), with minimal correlation to low-density-lipoprotein cholesterol. Clinical guidelines have recently been published indicating that CRP levels of <1, 1-3, and >3 mg/L correspond to low, moderate, and high risk, respectively, for future vascular events. Drugs including statins, fibrates, niacin, thiazolidinediones, and antiplatelet agents, as well as weight loss and exercise, have demonstrated efficacy in lowering CRP levels.

CONCLUSIONS

CRP appears to be a valuable tool for predicting future vascular events in patients striving for primary or secondary prevention of cardiovascular disease. While several pharmacologic and nonpharmacologic interventions have been shown to lower CRP levels, the impact on clinical outcomes requires further study.

C-Reactive Protein Upregulates Complement-Inhibitory Factors in Endothelial Cells

BACKGROUND

Because complement-mediated vascular injury participates in atherosclerosis and C-reactive protein (CRP) can activate the complement cascade, we sought to determine whether CRP affects the expression of the protective complement-inhibitory factors on the cell surface of endothelial cells (ECs).

METHODS AND RESULTS

Human coronary artery or human saphenous vein ECs were incubated with CRP (0 to 100 microg/mL, 0 to 72 hours), and the expression of the complement-inhibitory proteins decay-accelerating factor (DAF), membrane cofactor protein (CD46), and CD59 were measured by flow cytometry. Incubation with CRP resulted in a significant increase in the expression of all 3 proteins. CRP-induced upregulation of DAF required increased steady-state mRNA and de novo protein synthesis. The increased expression of complement-inhibitory proteins was functionally effective, resulting in significant reduction of complement-mediated lysis of antibody-coated human saphenous vein ECs.

CONCLUSIONS

These observations provide evidence for a possible protective role for CRP in atherogenesis.

C-reactive protein accelerates the progression of atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

Plasma C-reactive protein (CRP) concentration is a strong predictor of atherosclerosis. However, to date, there is no in vivo evidence that CRP is proatherogenic.

METHODS AND RESULTS

We studied the effect of human CRP transgene (tg) expression, under basal and turpentine-stimulated conditions, on atherosclerosis in apolipoprotein (apo) E-/- mice. Aortic atherosclerotic lesions in 29-week-old male mice were 48% larger (P<0.02) in turpentine-treated mice and 34% larger (P<0.05) in untreated CRPtg+/0/apoE-/- mice. Turpentine treatment per se did not affect the extent of atherosclerosis in CRP transgenic or nontransgenic apoE-/- mice. Transgenic mice exhibited lower plasma complement C3 but increased deposition of CRP and C3 in the lesions, which suggests that CRP stimulated activation of complement within the lesion. There was more intense and widespread vascular cell adhesion molecule-1 and collagen staining in the lesions of CRPtg+/0/apoE-/- mice than in CRPtg0/0/apoE-/- littermates. Lesions of CRPtg+/0/apoE-/- mice contained increased angiotensin type 1 receptor (AT1-R) transcripts and displayed increased AT1-R immunostaining compared with those of CRPtg0/0/apoE-/- mice. There was no difference in blood pressure in the 2 types of mice, which indicates that the proatherogenic effect of CRP-associated AT1-R overexpression is local and not mediated by its hypertensive properties.

CONCLUSIONS

Human CRP transgene expression causes accelerated aortic atherosclerosis in apoE-/- mice. CRP was detected in the lesion, which was associated with increased C3 deposition and increased AT1-R, vascular cell adhesion molecule-1, and collagen expression. These data document a proatherogenic role for CRP in vivo.

Leukocytes and coronary heart disease

Inflammation has been demonstrated to be an important risk factor for the development of cardiovascular events. Patients with elevated white blood cell counts have been shown to be in a higher risk of developing acute myocardial infarction and acute coronary and vascular events. We review the clinical data of high white blood cell counts and the prognosis, and demonstrate several possible mechanisms. It is possible that measuring white blood cell count and subpopulations could be used for a better way of risk stratification of patients admitted with acute vascular events.

C-reactive protein increases F-actin assembly and cortical distribution with resultant loss of lamellipod formation in human neutrophils

C-reactive protein (CRP) inhibits neutrophil movement through a p38 MAP kinase pathway. We hypothesized that CRP altered F-actin content and distribution on human neutrophils as a means of inhibiting movement. CRP produced simultaneous increased F-actin and decreased G-actin levels. CRP increased F-actin levels in a concentration-dependent manner once a threshold (>100 microg/ml) was reached, and transiently increased F-actin (peak levels at 2.5 and 10 min) that returned to baseline by 30 min. Confocal microscopy of neutrophils revealed that fMLP provoked acquisition of a migratory phenotype as evidenced by the appearance of F-actin rich lamellipods. In contrast, CRP caused neutrophil rounding, prevented lamellipod formation and shifted F-actin from the cytoskeleton to the cortex. The p38 MAP kinase inhibitor, SB203580, produced a similar effect on neutrophil shape. Concentrations of SB203580 that dramatically decreased p38 activity in neutrophils also caused round cell morphology and cortical F-actin distribution. Since CRP inhibits p38 MAP kinase and p38 blockade leads to actin polymerization and prevention of lamellipod formation, it is concluded that round morphology and loss of lamellipod formation result from CRP inhibition of p38 MAP kinase. Understanding the signal transduction of CRP prevention of lamellipod formation will aid in the development of therapeutic agents against neutrophil-associated inflammatory disease.

C-reactive protein activates the nuclear factor-κB signal transduction pathway in saphenous vein endothelial cells: implications for atherosclerosis and restenosis

OBJECTIVES

Elevated levels of C-reactive protein are one of the strongest prognostic factors in atherosclerosis. In addition to predicting vascular disease, C-reactive protein may directly facilitate the development of a proinflammatory and proatherosclerotic phenotype. Recent studies have demonstrated marked up-regulation of various adhesion molecules and inflammatory responses in endothelial cells subjected to C-reactive protein. The nuclear factor-kappaB signal transduction is known to play a key role in the expression of these proatherogenic entities. This study examines the direct effects of C-reactive protein on nuclear factor-kappaB activation and related mechanisms in saphenous vein endothelial cells.

METHODS

The activation of nuclear factor-kappaB was determined by confocal microscopy assessing the nuclear localization of nuclear factor-kappaB in endothelial cells incubated with C-reactive protein (50 microg/mL) for 30 minutes and 3 hours. Cells not incubated with C-reactive protein were used as negative controls, and cells incubated with tumor necrosis factor-alpha (10 ng/mL) for 15 minutes were used as positive controls in all studies. The degradation of IkappaB-alpha and IkappaB-beta was assessed by Western blotting of the cell lysates obtained from cells incubated with human recombinant C-reactive protein (50 microg/mL) for 15 minutes, 30 minutes, and 1 hour.

RESULTS

Nuclear factor-kappaB nuclear translocation in endothelial cells increased significantly after 30 minutes of incubation with C-reactive protein (P <.01). Nuclear localization of nuclear factor-kappaB returned to baseline levels after 3 hours of incubation with C-reactive protein. Incubation with C-reactive protein resulted in degradation of IkappaB-alpha that was maximal at 30 minutes (P <.05). C-reactive protein showed no significant effect on IkappaB-beta degradation.

CONCLUSIONS

These data demonstrate, for the first time, that C-reactive protein activates the nuclear factor-kappaB signal transduction pathway in endothelial cells. Degradation of IkappaB-alpha, but not IkappaB-beta, seems to be the major pathway leading to nuclear factor-kappaB nuclear translocation and activation induced by C-reactive protein. These data support the concept that C-reactive protein, at concentrations known to predict diverse vascular insults, directly facilitates a proinflammatory and proatherosclerotic phenotype through activation of nuclear factor-kappaB. These data have important implications for saphenous vein atherosclerosis in patients with elevated C-reactive protein levels.

Inflammatory interactions in fish exposed to pollutants and parasites: a role for apoptosis and C reactive protein

Although previous studies have highlighted the inflammatory responses of fish infected with parasites and exposed to pollutants, very little is known about how these two stressors interact within the fish. In this review, which also contains original data, the effect of these two parameters on the fish inflammatory response is assessed and, in particular, the role of apoptosis and the acute phase protein, C reactive protein, is evaluated. InCyprinus carpioexposed to 0·5 mg NH4+l−1or 0·1 mg Cd2+l−1and experimentally infected with the blood fluke,Sanguinicola inermis, the pollutant type and the order in which the fish experiences the parasite and toxicant, significantly affects the ultrastructural appearance and cellular content of the pronephros and thymus. This is reflected in the intensity of infection where the pollutant appears to have less effect on an established infection. Both stressors, pollutant and infection, may mediate their effects via the endocrine system. Studies have revealed that cortisol at 100 ng ml−1is able to induce apoptosis in pronephric cells of carp and that an increase in apoptosis is associated with an increase in phagocytosis in this immune organ. In addition, C reactive protein, which is used as a biomarker of the inflammatory response in humans and other mammals, is evaluated as a possible indicator of physiological states in fish exposed to pathogens and pollutants.

Significant dominance of fibrinogen over immunoglobulins, C-reactive protein, cholesterol and triglycerides in maintaining increased red blood cell adhesiveness/aggregation in the peripheral venous blood: a model in hypercholesterolaemic patients

BACKGROUND

It is not clear what is the relative importance of fibrinogen, immunoglobulins, highly sensitive C-reactive protein (hs-CRP), cholesterol and triglyceride concentrations on the appearance of aggregated red blood cells in the peripheral blood.

DESIGN

Six hypercholesterolaemic patients undergoing regular LDL apheresis that were examined repeatedly before and following the procedure.

RESULTS

We determined the degree of erythrocyte adhesiveness/aggregation in relation to the concentration of the above-mentioned macromolecules in 80 samples. In a linear logistic regression the respective R2 values for fibrinogen, total cholesterol, triglycerides, hs-CRP, IgG, IgM and IgA were 0.45 (P<0.0001), 0.2 (P<0.0001), 0.02 (P=0.02), 0.001 (P=NS) and 0.002 (P=NS), respectively. We further analyzed the potential of ApoA, ApoB and Lpa to participate in red cell adhesiveness/aggregation and found them to be not significant.

CONCLUSIONS

In a milieu of adhesive macromolecules, lipids and inflammation-sensitive proteins including fibrinogen, total cholesterol, triglycerides, hs-CRP and immunoglobins G, M and A, fibrinogen has a dominant role in maintaining the red blood cell adhesiveness/aggregation in the peripheral venous blood. These findings are relevant for the research directed at finding new apheretic modalities to reduce the degree of red blood cell adhesiveness/aggregation in the peripheral blood.

C-reactive protein and cardiovascular disease: new insights from an old molecule

The classical acute-phase protein, C-reactive protein (CRP), is an exquisitely sensitive systemic marker of disease with broad clinical utility for monitoring and differential diagnosis. Inflammation, the key regulator of CRP synthesis, plays a pivotal role in atherothrombotic cardiovascular disease. There is a powerful predictive association between raised serum CRP values and the outcome of acute coronary syndromes, and, remarkably, between even modestly increased CRP production and future atherothrombotic events in otherwise healthy individuals. Baseline CRP values also reflect metabolic states associated with atherothrombotic events. The presence of CRP within most atherosclerotic plaques and all acute myocardial infarction lesions, coupled with binding of CRP to lipoproteins and its capacity for pro-inflammatory complement activation, suggests that CRP may contribute to the pathogenesis and complications of cardiovascular disease. We review the biological properties of CRP, the association between CRP and cardiovascular disease, and the possibility that CRP may be a novel therapeutic target.

C-reactive protein and atherosclerosis. Is there a causal link?

C-reactive protein (CRP) is a powerful cardiovascular risk marker. Evidence suggests that this may be due to its direct proatherogenic properties. Because of different biological functions of CRP in different species, an appropriate animal model for the study of its role in atherogenesis is difficult to set up. Binding to low density lipoprotein (LDL), activation of the complement system and interaction with monocyte/macrophages are rigorously defined pathogenic properties of CRP which might contribute to an active role of the molecule in human atherogenesis. Furthermore, direct effects on arterial wall cells, i.e. endothelial cells and smooth muscle cells, have been reported. The molecular basis of CRP interaction with these cells, however, remains unclear. Should CRP indeed be actively involved in human atherogenesis, the molecule may become a target for therapy. Pharmaceutical companies develop CRP-inhibitors.

C-reactive protein and coronary artery calcification: The Study of Inherited Risk of Coronary Atherosclerosis (SIRCA)

OBJECTIVE

Circulating levels of C-reactive protein (CRP) predict cardiovascular events. In contrast, an association between CRP and direct measures of atherosclerosis has not been established clearly. In the largest study to date, we examined the association of plasma CRP with coronary artery calcification (CAC) in 914 asymptomatic subjects in the Study of Inherited Risk of Coronary Atherosclerosis (SIRCA).

METHODS AND RESULTS

In age-adjusted, cross-sectional analysis, there was a weak association between plasma CRP levels and CAC in women (odds ratio [OR] for ordinal regression, 1.1 [1.04 to 1.17] per 1.0 mg/L increase in CRP; P=0.005) but not in men. The association between CRP and CAC in women remained significant after adjusting for traditional risk factors (OR, 1.08 [1.00 to 1.14]; P=0.048) but was lost after further adjustment for body mass index (BMI) (OR, 1.02 [0.94 to 1.08]; P=0.7).

CONCLUSIONS

In SIRCA, CRP was not associated with CAC in men, and a weak association in women was lost after adjustment for BMI. The relation between CRP and clinical events might not be related to atherosclerotic burden. Measures of inflammation, such as CRP, and indices of atherosclerosis, such as CAC, are likely to provide distinct information regarding cardiovascular risk.