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

C-Reactive Protein Signaling Pathways in Tumor Progression

Many cancers arise from sites of chronic inflammation, which creates an inflammatory microenvironment surrounding the tumor. Inflammatory substances secreted by cells in the inflammatory environment can induce the proliferation and survival of cancer cells, thereby promoting cancer metastasis and angiogenesis. Therefore, it is important to identify the role of inflammatory factors in cancer progression. This review summarizes the signaling pathways and roles of C-reactive protein (CRP) in various cancer types, including breast, liver, renal, and pancreatic cancer, and the tumor microenvironment. Mounting evidence suggests the role of CRP in breast cancer, particularly in triple-negative breast cancer (TNBC), which is typically associated with a worse prognosis. Increased CRP in the inflammatory environment contributes to enhanced invasiveness and tumor formation in TNBC cells. CRP promotes endothelial cell formation and angiogenesis and contributes to the initiation and progression of atherosclerosis. In pancreatic and kidney cancers, CRP contributes to tumor progression. In liver cancer, CRP regulates inflammatory responses and lipid metabolism. CRP modulates the activity of various signaling molecules in macrophages and monocytes present in the tumor microenvironment, contributing to tumor development, the immune response, and inflammation. In the present review, we overviewed the role of CRP signaling pathways and the association between inflammation and cancer in various types of cancer. Identifying the interactions between CRP signaling pathways and other inflammatory mediators in cancer progression is crucial for understanding the complex relationship between inflammation and cancer.

Coagulation Disorders in Sepsis and COVID-19-Two Sides of the Same Coin? A Review of Inflammation-Coagulation Crosstalk in Bacterial Sepsis and COVID-19

Sepsis is a major cause of morbidity and mortality worldwide. Sepsis-associated coagulation disorders are involved in the pathogenesis of multiorgan failure and lead to a subsequently worsening prognosis. Alongside the global impact of the COVID-19 pandemic, a great number of research papers have focused on SARS-CoV-2 pathogenesis and treatment. Significant progress has been made in this regard and coagulation disturbances were once again found to underlie some of the most serious adverse outcomes of SARS-CoV-2 infection, such as acute lung injury and multiorgan dysfunction. In the attempt of untangling the mechanisms behind COVID-19-associated coagulopathy (CAC), a series of similarities with sepsis-induced coagulopathy (SIC) became apparent. Whether they are, in fact, the same disease has not been established yet. The clinical picture of CAC shows the unique feature of an initial phase of intravascular coagulation confined to the respiratory system. Only later on, patients can develop a clinically significant form of systemic coagulopathy, possibly with a consumptive pattern, but, unlike SIC, it is not a key feature. Deepening our understanding of CAC pathogenesis has to remain a major goal for the research community, in order to design and validate accurate definitions and classification criteria.

The impact of the cumulative burden of LDL-c and hs-CRP on cardiovascular risk: a prospective, population-based study

Background: This study aims to demonstrate the impact of the cumulative burden of low density lipoprotein-cholesterol (cumLDL-c) and high sensitivity C-reactive protein (cumhs-CRP) on cardiovascular risk.

Results: During the 4.62 (±0.70) years of follow-up, 2,148 (5.92%) participants had MACE. Both of cumLDL-c and cumhs-CRP were independent risk factors for MACE. In participants without cumLDL-c during 2006-2013, the participants with cumhs-CRP had higher MACE risk during the subsequent 5 years, than those without cumhs-CRP (hazard ratio [HR]: 1.24, 95% confidence interval [CI]:1.04-1.47). In addition, cumhs-CRP correlated with MACE in a cumhs-CRP level-dependent pattern.

Conclusion: This study validated the effects of residual inflammation risk in patients with low LDL-c Level in a general population, using long-term burdens of hs-CRP or LDL-c other than a single time-point level.

Method: The Kailuan study is a prospective, population-based study began in 2006. These total 36,421 participants completed 4 measurements of hs-CRP and LDL-c biennially from 2006-2013. Cumhs-CRP or cumLDL-c levels were calculated as the number of interval years multiplied by the Δhs-CRP (more than 2.0 mg/L) or ΔLDL-c (more than 2.6 mmol/L). Outcomes measured during follow-up (2012-2017) were defined as major adverse cardiac events (MACE), including ischemic stroke, myocardial infarction, and all-cause mortality.

N1-methylnicotinamide as a possible modulator of cardiovascular risk markers in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a multifactorial disease, which is resulted from the three common features, hyperandrogenism (HA), ovulatory dysfunction (OD), and polycystic ovarian morphology (PCOM). The environmental inducers (like diet, lifestyle, chemicals, drugs, and ageing) and cardiometabolic risk factors (such as insulin resistance, metabolic syndrome, and obesity) are involved in pathogenesis of PCOS. The growing body of evidence has been shown that there exist endothelial cell dysfunction (ECD) in women with PCOS independent of age, weight and metabolic abnormalities. It has been shown that a broad spectrum of cardiovascular risk markers are involved in ECD- induced cardiovascular disease. It is well described that there are no worldwide treatments for PCOS and all of pharmacological treatments are off -label without any approval. MNAM is one of potential therapeutic factor, which produced by nicotinamide N-methyltransferase (NNMT) via consumption of S-adenosyl methionine (SAM) and nicotinamide. Only one study has shown higher expression of its producer enzyme, NNMT, in the cumulus cells of women with PCOS. Therefore, we reviewed beneficial effects of MNAM on modulation of cardiometabolic risk factors, which are associated to PCOS and try to describe possible mode of action of MNAM in the regulation of these markers.

The Multiple Faces of C-Reactive Protein-Physiological and Pathophysiological Implications in Cardiovascular Disease

C-reactive protein (CRP) is an intriguing protein which plays a variety of roles in either physiological or pathophysiological states. For years it has been regarded merely as a useful biomarker of infection, tissue injury and inflammation, and it was only in the early 80s that the modified isoforms (mCRP) of native CRP (nCRP) appeared. It soon became clear that the roles of native CRP should be clearly discriminated from those of the modified form and so the impacts of both isoforms were divided to a certain degree between physiological and pathophysiological states. For decades, CRP has been regarded only as a hallmark of inflammation; however, it has since been recognised as a significant predictor of future episodes of cardiovascular disease, independent of other risk factors. The existence of modified CRP isoforms and their possible relevance to various pathophysiological conditions, suggested over thirty years ago, has prompted the search for structural and functional dissimilarities between the pentameric nCRP and monomeric mCRP isoforms. New attempts to identify the possible relevance between the diversity of structures and their opposing functions have initiated a new era of research on C-reactive protein. This review discusses the biochemical aspects of CRP physiology, emphasizing the supposed relevance between the structural biology of CRP isoforms and their differentiated physiological and pathophysiological roles.

Polycystic ovarian syndrome-associated cardiovascular complications: An overview of the association between the biochemical markers and potential strategies for their prevention and elimination

Polycystic ovarian syndrome (PCOS) is associated with multiple cardiovascular risk factors (CVRF) including endothelial dysfunction (ED) and presence of metabolic syndrome (MS). The probable reason suggested for elevated CVRF in PCOS is oxidative stress (OS), which is an integral factor in cardiometabolic complications (CMC) seen in PCOS women. The interrelated mechanisms by which CVRF instigate clinical manifestation plays a crucial role in identification of a strategy to treat different comorbidities in PCOS. The existing treatment for PCOS mostly focuses on management of individual disorders, however, therapeutic strategies or novel targets to address cardiovascular complications in PCOS deserve extensive analysis.

C reactive protein and long-term risk for chronic kidney disease: a historical prospective study

INTRODUCTION

C reactive protein (CRP) is an acute phase reactant that primarily produced by hepatocytes yet may be locally expressed in renal tubular cells. We assessed the association of CRP and the risk for chronic kidney disease (CKD) development.

METHODS

Historical prospective cohort study was conducted on subjects attending a screening center in Israel since the year 2000. Subjects with an estimated GFR (eGFR) above 60 ml/min/1.73 m(2) at baseline were included, and high sensitive (hs) CRP levels as well as eGFR were recorded for each visit. Follow up continued for at least 5 years for each subject until 2013. Risk for CKD at end of follow up was assessed in relation to mean hs-CRP levels of each subject. The confounding effects of other predictors of CKD were examined. A logistic regression model treating CRP as a continuous variable was further applied.

RESULTS

Out of 4,345 patients, 42 (1%) developed CKD in a mean follow up of 7.6 ± 2 years. Elevated levels of CRP were associated with greater risk for CKD (crude OR 4.17, 95% CI 1.46-11.89). The OR for the association of CRP with CKD when controlling for age and gender was 5.2 (95% CI 1.7-16.2). When controlling for established renal risk factors, elevated CRP levels remained significantly associated with greater risk for CKD (OR 5.42, 95% CI 1.76-16.68). When applying logistic regression models treating CRP as a continuous variable, for patients with diabetes mellitus (DM), hypertension (HTN) or eGFR between 60-90 ml\min\1.73 m(2), the predictive role of CRP for CKD was highly significant.

CONCLUSION

Elevated CRP level is an independent risk factor for CKD development. In patients with DM, HTN or baseline eGFR between 60-90 ml\min\1.73 m(2) its predictive role is enhanced.

Rac1 is a possible link between obesity and oxidative stress in Chinese overweight adolescents

Enhanced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in the monocytes occurred in metabolic syndrome, hypertension, diabetes and obese patients in adults. However, whether NADPH oxidase is involved in the oxidative stress of overweight adolescents without comorbidities is still unclear. This study aimed to identify whether and how NADPH oxidase plays a crucial role in overweight adolescents. The study was performed in 93 overweight adolescents and 31 normal weight controls. Moreover, 87 overweight adolescents were enrolled in weight-loss program. Demographics characteristics, anthropometrics, composition and clinical characteristics were analyzed. Oxidative stress indexes including the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in plasma and the expression of NADPH oxidase in the monocytes were examined. Overweight adolescents showed a higher oxidative stress state, as indicated by decreased SOD activity and elevated MDA level (P < 0.01). Furthermore, increased NADPH oxidase activity in the monocytes was accompanied by Rac1 upregulation. A significant positive bivariate correlation was found between Rac1 expression and MDA (r = 0.289). There also was a significant positive bivariate correlation between Rac1 expression and obesity-related indexes including BMI (r = 0.227) and percentage of trunk fat (r = 0.233). Data from weight-loss program reinforced the results. Partial correlation analysis indicated that obesity-induced oxidative stress and Rac1 expression is a consequence of aberrant glucose-lipid metabolism in overweight adolescents. In conclusion, we provided novel data showing that NADPH oxidase in the monocytes was highly activated by enhancing Rac1 expression in Chinese overweight adolescents and Rac1 may act as a link between obesity and oxidative stress in overweight adolescents.

Monomeric C-reactive protein alters fibrin clot properties on endothelial cells

Elevated plasma levels of C-reactive protein (CRP) are independently associated with increased risk of atherothrombosis. Several lines of evidence suggest that CRP has prothrombogenic effects on injured vessel wall(s) by enhancing tissue factor (TF) expression. Abnormal fibrin formation is correlated with increased thrombotic risk. However, the impact of localized, cell surface-driven in situ tissue factor generation by CRP on clot dynamics and fibrin architecture has not previously been evaluated. We examined the impact of native CRP and modified or monomeric CRP (mCRP) on the fibrin formation and structure in Human Umbilical Vein Endothelial Cells (HUVECs). Fibrin formation and structure were examined using laser scanning confocal microscopy. Incubation with mCRP on the cell surface had faster fibrin polymerization by the analysis of turbidimetry. Confocal microscopy of fibrin clots showed a significantly increased density in the treatment of mCRP compared with native CRP and control in the proximal versus distal relationship to the cell surface. The increased expression and activity of TF on the cell surface was observed by addition of mCRP. Blockage of tissue factor and lipid rafts significantly reduced the density of fibrin network produced by mCRP-stimulated endothelial cells. mCRP changes clot dynamics and alters fibrin architecture by enhancing TF on the endothelial cell surface. These results support the concept that elevated CRP levels may induce fibrinolytic resistance and endothelial dysfunction by altering fibrin clot structure.

Apolipoprotein A-I, apolipoprotein B, high-sensitivity C-reactive protein and severity of coronary artery disease in Tunisian population

BACKGROUND

The relationship between Apolipoprotein A-I, Apolipoprotein B, C-reactive protein and the severity coronary artery disease in Tunisian CAD patients has not been examined. We investigated the association between serum ApoA-I, ApoB, hs-CRP and the severity of coronary artery disease.

METHODS

This study was carried out on 180 patients who underwent angiography and 129 healthy controls. ApoA-I and ApoB as well as the serum total cholesterol, HDL, triglyceride, LDL and hs-CRP levels were measured. The ApoB/ApoA-I ratio was calculated.

RESULTS

We showed a decreased level of ApoA-I and an increased level of ApoB, ApoB/ApoA-I ratio and hs-CRP in CAD patients compared to the control group (P<.001). In addition, we showed a significant increase of ApoB, ApoB/ApoA-I ratio and hs-CRP in CAD patients presenting 0 to 3 vessels stenosis (P<.001). Multivariate analysis showed that ApoB (P<.001), and hs-CRP (P<.001) were independent predictors of the severity of CAD.

CONCLUSION

In this study, ApoB and hs-CRP levels were markedly associated with the severity of CAD in Tunisian patients. We suggested that synergistic effects between dyslipidemia and inflammation led to increase the risk of the severity of CAD.

Impaired glucose metabolism and type 2 diabetes are associated with hypercoagulability: potential role of central adiposity and low-grade inflammation--the Hoorn Study

INTRODUCTION

Type 2 diabetes (DM2) is associated with greater risk for cardiovascular disease (CVD), which may, at least partially, be explained by prothrombotic alterations. We therefore investigated; first, the extent to which individuals with impaired glucose metabolism (IGM) and/or DM2 had greater levels of thrombin generation than those with normal glucose metabolism (NGM); and second, whether any differences were independent of other cardiovascular risk factors, such as smoking, hypertension, dyslipidaemia, (micro)albuminuria, glycemic control and (central) adiposity, and/or were potentially 'mediated' by low-grade inflammation (high-sensitivity C-reactive protein (hsCRP)).

MATERIALS AND METHODS

We studied 744 individuals from the Hoorn Study (275 NGM, 176 IGM and 293 DM2, mean age 68.6 ± 7.1 years). Thrombin generation in platelet-poor plasma was measured using the Calibrated Automated Thrombogram and three parameters were derived: lag time, peak height and endogenous thrombin potential (ETP). Data were analyzed with multiple linear regression analyses.

RESULTS

After adjustment for age, sex, prior CVD and smoking status, individuals with IGM or DM2 had a longer lag time [ß = 0.14 min (95% CI: 0.02; 0.26)], higher peak height [ß = 7.29 nM (-1.33; 15.91)] and ETP [ß = 35.65 nM*min (0.97; 70.34)] than those with NGM. These differences were attenuated to ß = 0.06 min (-0.07; 0.19), 3.82 nM (-5.46; 13.10) and 16.34 nM*min (-20.92; 53.59), respectively, when further adjusted for waist circumference and hsCRP.

CONCLUSION

Individuals with IGM or DM2 had up to 4% higher thrombin generation compared with NGM, which may be explained, to a great extent, by the greater levels of central adiposity and related low-grade inflammation characterizing these individuals.

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.

Increased tissue factor activity in monocytes from obese young adults

1. The relationship between inflammation, obesity-related proteins and tissue factor (TF), the major initiator of the extrinsic clotting cascade, is not well understood. We examined if basal and stimulated peripheral blood mononuclear cell (PBMC) TF-procoagulant activity (PCA) was higher in obese subjects and examined the effects of leptin, resistin and serum amyloid A (SAA). 2. PBMC from 12 obese (six male, aged 29±4years, body mass index 46.0±8.7kg/m(2) ) and 12 age- and sex-matched lean controls were cultured either unstimulated or stimulated by lipopolysaccharide (LPS; 10ρg/mL and 100ng/mL, for 4-16h) or SAA (1 ng/mL, 25ng/mL, 250ng/mL, for 4h). Separately, PBMC from lean subjects were cultured unstimulated with leptin (100ρg/mL, 1ng/mL, 10ng/mL, 100ng/mL, 1 μg/mL), resistin (0.1ng/mL, 1ng/mL, 10ng/mL, 100ng/mL) or leptin (100ng/mL) plus LPS (100ρg/mL). TF-PCA was determined by a 1-stage plasma recalcification assay. 3. Four-hour unstimulated PBMC TF-PCA was greater in the obese (90.4±16.5 vs 39.9±4.7mu TF/10(6) PBMC, P=0.01). After 4h stimulation with SAA or LPS the TF-PCA was similar. Unstimulated TF-PCA correlated with log serum high sensitivity C- reactive protein (hs-CRP) (r=0.42, P=0.04) and insulin (r=0.44, P=0.048), but not with log serum SAA (r=0.192, P=0.55). Physiological concentrations of leptin or resistin and leptin plus LPS did not increase TF-PCA in PBMC from lean subjects. 4. Basal PBMC TF-PCA is higher in the obese and is associated with serum hs-CRP. The obesity-related proteins SAA, leptin and resistin are unlikely to play a major role in increasing PBMC TF-PCA.

Body composition as determinant of thrombin generation in plasma: the Hoorn study

OBJECTIVE

The association between obesity and cardiovascular disease and venous thromboembolism might, at least partially, be explained by a hypercoagulable state. The extent to which body fat mass and its distribution contribute to a hypercoagulable state is unknown. In this study, we investigated the association between body composition and thrombin generation and evaluated the potential mediating role of low-grade inflammation.

METHODS AND RESULTS

We studied 586 individuals from the Hoorn Study (mean age, 69.7 ± 6.5 years, 298 women) in whom body composition was assessed by whole body dual-energy absorptiometry. Thrombin generation was measured using the calibrated automated thrombogram. Multiple regression analyses showed a positive association between total body fat and thrombin generation in women but not in men. In addition, detailed analyses of regional body composition showed that central but not peripheral fat mass was associated with greater thrombin generation and that there was a trend toward an inverse association with peripheral lean mass. The reported positive associations were partially attenuated by low-grade inflammation, however.

CONCLUSIONS

Body fat mass, in particular a central pattern of fat distribution, is associated with higher levels of thrombin generation in elderly women but not in men. This association may partially be explained by adiposity-related low-grade inflammation, but this hypothesis needs to be further investigated in mechanistic/prospective studies.

The evolving role of C-reactive protein in atherothrombosis

BACKGROUND

Inflammation is pivotal in all phases of atherosclerosis. Among the numerous inflammatory biomarkers, the largest amount of published data supports a role for C-reactive protein (CRP) as a robust and independent risk marker in the prediction of primary and secondary adverse cardiovascular events. In addition to being a risk marker, there is much evidence indicating that CRP may indeed participate in atherogenesis.

CONTENT

In this review, we focus on the role of CRP in promoting atherothrombosis by discussing its effects on endothelial cells, endothelial progenitor cells, monocyte-macrophages, and smooth muscle cells.

CONCLUSIONS

CRP is clearly a risk marker for cardiovascular disease and is recommended for use in primary prevention. In addition, CRP appears also to contribute to atherogenesis. However, much further research is needed, especially in appropriate animal models, to confirm the possible role of CRP in promoting atherothrombosis.

C-reactive protein stimulates superoxide anion release and tissue factor activity in vivo

C-reactive protein (CRP), the prototypic marker of inflammation, is a cardiovascular risk marker and recent in vitro studies suggest that it may promote atherogenesis. CRP promotes oxidative stress in vitro and induces tissue factor (TF) release. However, there is a paucity of data examining the effects of CRP on oxidative stress and tissue factor procoagulant activity (PCA) in vivo. Thus, we tested the effects of CRP administration on superoxide anion release and tissue factor activity and examined mechanistic pathways using a rat sterile air pouch model. Intraperitoneal administration of CRP (20mg/kg body weight) compared to human serum albumin (HuSA) increased superoxide anion release and tissue factor activity from peritoneal macrophages in vivo (p<0.01). This was confirmed using intrapouch administration of CRP (25mug/mL) compared to HuSA. Pretreatment with reactive oxygen species (ROS) scavengers or protein kinase C (PKC) inhibitor significantly abrogated CRP-induced superoxide anion release and tissue factor activity. Pretreatment with extracellular signal-regulated kinase (ERK) and Jun N-terminal kinase (JNK) inhibitors, but not p38 mitogen-activated protein kinase (p38MAPK) significantly decreased CRP-induced superoxide anion release from macrophages in vivo. CRP-induced tissue factor activity in vivo was abrogated by pretreatment with inhibitors to p38MAPK, JNK and NFkappab (nuclear factor-kappab), but not ERK. Antibodies to Fc gamma receptors, CD32 and CD64 resulted in significant reduction in CRP-induced superoxide and tissue factor activity in vivo. Thus, CRP appears to induce oxidative stress in vivo by stimulating NADPH oxidase via PKC, ERK and JNK phosphorylation, and induces tissue factor PCA in vivo via upregulation of PKC, p38MAPK, JNK, ROS and NFkappab. CRP-induced ROS appears to precede tissue factor release. These effects are abrogated by blocking Fc gamma receptors, CD32 and CD64. This in vivo demonstration provides further evidence for a role for CRP in atherothrombosis.

Tissue Factor and Monocyte Chemoattractant Protein-1 Expression in Hypertensive Individuals with Normal or Increased Carotid Intima-Media Wall Thickness

Background: People with hypertension display an inflammatory pattern that includes increased plasma concentrations of monocyte chemoattractant protein 1 (MCP-1) and C-reactive protein (CRP) and enhanced expression of tissue factor (TF) mRNA in blood monocytes.

Methods: In this study, we investigated the relationship between CRP concentrations and TF and MCP-1 mRNA expression in unstimulated and lipopolysaccharide (LPS)-stimulated monocytes isolated from hypertensives with or without an increase in carotid intima-media thickness (IMT). We also investigated the expression of TF and MCP-1 mRNA and MCP-1 protein after in vitro addition of CRP to monocytes. We measured CRP (by immunonephelometry) and monocyte expression of TF and MCP-1 (by real-time PCR) in 80 untreated hypertensive patients without clinical cardiovascular disease (CVD) or additional risk factors for CVD compared with 41 controls. Based on IMT measured by carotid Doppler ultrasonography, patients were classified into the categories of normal (≤1 mm) or abnormal (&gt;1 mm). TF and MCP-1 mRNA and MCP-1 protein (by Western blotting) were measured after in vitro addition of CRP to monocytes from 10 randomized controls as well as 10 hypertensives with IMT ≤1 mm and 10 with IMT &gt;1 mm.

Results: CRP and TF and MCP-1 mRNA concentrations were significantly higher in IMT &gt;1 mm hypertensives vs those with IMT ≤1 mm and controls. CRP had no effect on monocyte TF mRNA from either hypertensives or controls. CRP-stimulated monocytes from hypertensives, however, showed increased MCP-1 mRNA and protein expression compared with controls and LPS-stimulated cells.

Conclusions: Our findings suggest that the inflammatory response of blood monocytes plays an important role in the development of atherosclerosis and hypertension.

C-reactive protein and atherogenesis: from fatty streak to clinical event

In recent years, it has become increasingly clear that arterial inflammation represents a key feature determining the course of atherogenesis. The consecutive stages in the evolution of atherosclerotic lesions are respectively, plaque buildup and growth, and destabilization, predisposing to plaque rupture and intravascular thrombosis. This chain of events leading from lesion formation to clinical events has been carefully elucidated during the last three decades. C-reactive protein (CRP) has been directly implicated in the pathogenesis of atherosclerosis. In the present review, we will focus on a potentially causal role of CRP during the various stages of atherogenesis.

Serum Amyloid A Induces Monocyte Tissue Factor

C-reactive protein (CRP) and serum amyloid A (SAA) increase in the blood of patients with inflammatory conditions and CRP-induced monocyte tissue factor (TF) may contribute to inflammation-associated thrombosis. This study demonstrates that SAA is a potent and rapid inducer of human monocyte TF. SAA induced TF mRNA in PBMC within 30 min and optimal procoagulant activity within 4 h, whereas CRP (25 mug/ml)-induced activity was minimal at this time. Unlike CRP, SAA did not synergize with LPS. Procoagulant activity was inhibited by anti-TF and was dependent on factors VII and X, and TF Ag levels were elevated on CD14(+) monocytes. Responses were optimal with lymphocytes, although these were not obligatory. Inhibitor studies indicate activation of NF-kappaB through the ERK1/2 and p38 MAPK pathways; the cyclo-oxygenase pathway was not involved. SAA-induced TF was partially inhibited by high-density lipoprotein, but not by low-density lipoprotein or by apolipoprotein A-I. SAA is a ligand for the receptor for advanced glycation end products (RAGE), and TF generation was suppressed by approximately 50% by a RAGE competitor, soluble RAGE, and by approximately 85% by anti-RAGE IgG. However, another RAGE ligand, high mobility group box-1 protein, capable of inducing monocyte chemotactic protein-1 mRNA in 2 h, did not induce TF within 24 h. Cross-linking studies confirmed SAA binding to soluble RAGE. Elevated SAA is a marker of disease activity in patients with rheumatoid arthritis, and PBMC from patients with rheumatoid arthritis were more sensitive to SAA than normals, suggesting a new link between inflammation and thrombosis.

Oral streptococci and cardiovascular disease: searching for the platelet aggregation-associated protein gene and mechanisms of Streptococcus sanguis-induced thrombosis

BACKGROUND

Pathogenic mechanisms in infective endocarditis, disseminated intravascular coagulation, and cardiovascular events involve the aggregation of platelets into thrombi. Attendant infection by oral bacteria contributes to these diseases. We have been studying how certain oral streptococci induce platelet aggregation in vitro and in vivo. Streptococcus sanguis expresses a platelet aggregation-associated protein (PAAP), which contributes little to adhesion to platelets. When specific antibodies or peptides block PAAP, S. sanguis fails to induce platelet aggregation in vitro or in vivo.

METHODS

We used subtractive hybridization to identify the gene encoding for PAAP.

RESULTS

After subtraction of strain L50 (platelet aggregation-negative), four strain 133-79 specific sequences were characterized. Sequence agg4 encoded a putative collagen-binding protein (CbpA), which was predicted to contain two PAAP collagen-like octapeptide sequences. S. sanguis CbpA- mutants were constructed and tested for induction of platelet aggregation in vitro. Platelet aggregation was substantially inhibited when compared to the wild-type using platelet-rich plasma from the principal donor, but adhesion was unaffected. Other donor platelets responded normally to the CbpA- strain, suggesting additional mechanisms of response to S. sanguis. In contrast, CshA- and methionine sulfoxide reductase-negative (MsrA-) strains neither adhered nor induced platelet aggregation.

CONCLUSIONS

CbpA was suggested to contribute to site 2 interactions in our two-site model of platelet aggregation in response to S. sanguis. Platelet polymorphisms were suggested to contribute to the thrombogenic potential of S. sanguis.

C-reactive protein contributes to the hypercoagulable state in coronary artery disease

OBJECTIVES

Elevated plasma C-reactive protein (CRP) levels predict coronary events, but it is unclear whether CRP plays a role in thrombosis associated with these events. We investigated tissue factor (TF) induction by CRP on peripheral blood mononuclear cells (PBMC) from patients with coronary disease.

PATIENTS AND METHODS

PBMC from 35 patients with stable angina (SA) in study 1, 10 male patients with SA, 10 with unstable angina (UA) and 10 matched controls in study 2, and 25 patients with inflammatory disorders (ID) and 24 normal controls in study 3 were stimulated with CRP, interferon-gamma (IFN) or lipopolysaccharide (LPS), or their combination. PBMC from additional normal donors were also stimulated with CRP in adherent and non-adherent conditions, and TF activity, antigen and mRNA expression detected.

RESULTS

CRP (5-25 microg mL(-1)) dose dependently induced more TF on PBMC from SA patients than 42 contemporary controls (P = 0.001, study 1). Compared with controls, patients with SA or UA had higher basal, and much higher CRP- or CRP/LPS-induced monocyte TF activity although serum CRP levels were similar (study 2). IFN induced monocyte TF activity in patients with angina, but not in controls. Basal or CRP-induced TF levels did not differ between controls and ID, even though ID patients had much higher serum CRP levels (study 3). CRP-induced monocyte TF activity correlated with serum CRP levels in controls (P = 0.005) and ID (P = 0.007) in study 3, but not in patients with angina (P =0.84) in study 2. CRP induced more TF activity, protein and mRNA under adherent than non-adherent conditions implying that it may mainly target macrophages in lymphocyte-rich lesions.

CONCLUSIONS

Our results indicate that monocytes from patients with angina are preactivated and express TF but CRP is unlikely to be a major priming factor in vivo. IFN and CRP further increase TF levels that may contribute to the hypercoagulable state in coronary disease.

C-reactive protein and cardiovascular disease: a critical appraisal

PURPOSE OF REVIEW

C-reactive protein, a nonspecific marker of inflammation, has recently been proposed both as a marker of low-grade inflammation involved in atherogenesis and as a predictor of disease progression.

RECENT FINDINGS

The physiologic functions of C-reactive protein as an anti-inflammatory scavenger molecule have begun to emerge. For example, C-reactive protein binds to damaged lipoproteins and facilitates their removal by phagocytes without full complement activation. Increased levels of C-reactive protein may result in direct effects on vascular cells, including induction of cytokines and prothrombotic factors. Several sources of biologic variation in the levels of C-reactive protein have been identified, chief among which are abdominal obesity and the metabolic syndrome. Although previous studies showed a potent independent association of C-reactive protein levels with cardiac events, the strength of association was shown to be much weaker than previously reported in recent large meta-analyses. Therapy with nonspecific anti-inflammatory agents such as statins in patients with coronary artery disease has been found to reduce adverse outcomes in association with reductions in C-reactive protein, on the basis of retrospective analysis of stored blood specimens.

SUMMARY

Despite a relatively strong epidemiologic association with future adverse cardiovascular events, the great majority of apparently healthy individuals with elevated C-reactive protein will not experience cardiovascular disease. Even though more than 15 000 articles in PubMed mention C-reactive protein, current knowledge is insufficient to implicate C-reactive protein as a causative factor in atherothrombosis or to enable the recommendation of C-reactive protein testing to guide preventive or therapeutic interventions in cardiovascular diseases.

Synergistic enhancement of cytokine-induced human monocyte matrix metalloproteinase-1 by C-reactive protein and oxidized LDL through differential regulation of monocyte chemotactic protein-1 and prostaglandin E2

C-reactive protein (CRP) and oxidized LDL (ox-LDL) are associated with inflammatory lesions, such as coronary artery disease, in which monocytes and matrix metalloproteinases (MMPs) may play a major role in the rupture of atherosclerotic plaques. Monocytes are recruited to inflammation sites by monocyte chemoattractant protein-1 (MCP-1), which may also participate in the activation of monocytes. The objective of this study was to compare the individual and combined effect of CRP and ox-LDL on human monocyte MMP-1 and the role of MCP-1 in this effect. Although CRP or ox-LDL failed to induce MMP-1 in control monocytes, these molecules enhanced MMP-1 production induced by tumor necrosis factor alpha (TNF-alpha) and granulocyte macrophage-colony stimulating factor (GM-CSF) with a synergistic increase in MMP-1 occurring in the presence of both mediators. Enhancement of MMP-1 by CRP and ox-LDL was attributable to a differential increase in MCP-1 and prostaglandin E2(PGE2). CRP, at physiological concentrations, induced high levels of MCP-1 and relatively low levels of PGE2, whereas ox-LDL caused a significant enhancement of PGE2 with little affect on MCP-1. Accordingly, CRP- and ox-LDL-induced MMP-1 production by monocytes was inhibited by anti-MCP-1 antibodies and indomethacin, respectively. Moreover, addition of exogenous MCP-1 or PGE2 enhanced MMP-1 production by TNF-alpha- and GM-CSF-stimulated monocytes. These results show that the combination of CRP and ox-LDL can cause a synergistic enhancement of the role of monocytes in inflammation, first, by increasing MCP-1, which attracts more monocytes and directly enhances MMP-1 production by activated monocytes, and second, by elevating PGE2 production, which also leads to higher levels of MMP-1.

Effect of C-reactive protein on vascular cells: evidence for a proinflammatory, proatherogenic role

PURPOSE OF REVIEW

C-reactive protein (CRP) is the prototypic downstream marker of inflammation. High levels of CRP predict future cardiovascular risk in apparently healthy men and women. Recent evidence from different cell types suggests that CRP is not only a risk marker but may also be a participant in atherogenesis. This review will focus on the effects of CRP on different cells involved in atherosclerosis.

RECENT FINDINGS

CRP is shown to induce matrix metalloproteinase-1 (MMP-1) expression through the Fc gamma RII and extracellular signal-related kinase pathway in U937 cells. MMPs are implicated in plaque instability. A recent report shows that CRP does not induce tissue factor in human monocytes directly, disputing the previous concept that CRP induces tissue factor in monocytes. CRP is shown to upregulate interleukin-8 in human aortic endothelial cells via nuclear factor-kappa B. CRP promotes monocyte chemoattractant protein-1-mediated chemotaxis by upregulating CC-chemokine receptor 2 expression in human monocytes. Also CRP is shown to attenuate endothelial progenitor cell survival, differentiation, and function via inhibiting nitric oxide. Human CRP transgenic animal models show that CRP promotes atherothrombosis and increases plasminogen activator inhibitor-1. Also, the classic dogma that CRP is produced exclusively in liver is challenged by recent data on the extrahepatic production of CRP in different cells including atherosclerotic lesions.

SUMMARY

All this recent evidence along with earlier reports support a role for CRP in atherosclerosis.

C-reactive protein as a risk factor versus risk marker

PURPOSE OF REVIEW

C-reactive protein (CRP) is consistently associated with cardiovascular disease in prospective and cross-sectional clinical and epidemiological studies. Inflammation is an important mechanism in cardiovascular disease, and the plasma level of CRP is considered to reflect the inflammatory condition of the patient and/or the vessel wall. In addition, there are also a number of indications for a causal role of CRP in cardiovascular disease.

RECENT FINDINGS

A number of new publications show potential causal effects of CRP on cardiovascular disease, and evidence from human-CRP transgenic animals also indicates a causal contribution of CRP to cardiovascular disease. On the other hand, a new large prospective study and an updated meta-analysis indicate that the contribution of CRP to cardiovascular disease is less impressive than reported earlier (odds ratio, 1.58; 95% confidence interval, 1.48-1.68).

SUMMARY

We review here the most recent evidence on mechanisms by which CRP is involved as a causal factor in the precipitation of cardiovascular disease. Evidence for such a role is accumulating.