C-Reactive Protein: A Family of Proteins to Regulate Cardiovascular Function

Efficient expression and purification of rat CRP in Pichia pastoris

C-reactive protein (CRP) plays a crucial role in the diagnosis and monitoring of the non-specific acute phase response in humans. In contrast, rat CRP (rCRP) is an atypical acute-phase protein that possesses unique features, such as a possible incapacity to trigger the complement system and markedly elevated baseline plasma concentrations. To facilitate in vitro studies on these unique characteristics, obtaining high-quality pure rCRP is essential. Here we explored various strategies for rCRP purification, including direct isolation from rat plasma and recombinant expression in both prokaryotic and eukaryotic systems. Our study optimized the recombinant expression system to enhance the secretion and purification efficiency of rCRP. Compared to traditional purification methods, we present a streamlined and effective approach for the expression and purification of rCRP in the Pichia pastoris system. This refined methodology offers significant improvements in the efficiency and effectiveness of rCRP purification, thereby facilitating further structural and functional studies on rCRP.

Overexpression of miR-199b-5p in Colony Forming Unit-Hill's Colonies Positively Mediates the Inflammatory Response in Subclinical Cardiovascular Disease Model: Metformin Therapy Attenuates Its Expression

Well-controlled type 1 diabetes (T1DM) is characterized by inflammation and endothelial dysfunction, thus constituting a suitable model of subclinical cardiovascular disease (CVD). miR-199b-5p overexpression in murine CVD has shown proatherosclerotic effects. We hypothesized that miR-199b-5p would be overexpressed in subclinical CVD yet downregulated following metformin therapy. Inflammatory and vascular markers were measured in 29 individuals with T1DM and 20 matched healthy controls (HCs). miR-199b-5p expression in CFU-Hill's colonies was analyzed from each study group, and correlations with inflammatory/vascular health indices were evaluated. Significant upregulation of miR-199b-5p was observed in T1DM, which was significantly downregulated by metformin. miR-199b-5p correlated positively with vascular endothelial growth factor-D and c-reactive protein (CRP: nonsignificant). ROC analysis determined miR-199b-5p to define subclinical CVD by discriminating between HCs and T1DM individuals. ROC analyses of HbA1c and CRP showed that the upregulation of miR-199b-5p in T1DM individuals defined subclinical CVD at HbA1c > 44.25 mmol and CRP > 4.35 × 106 pg/mL. Ingenuity pathway analysis predicted miR-199b-5p to inhibit the target genes SIRT1, ETS1, and JAG1. Metformin was predicted to downregulate miR-199b-5p via NFATC2 and STAT3 and reverse its downstream effects. This study validated the antiangiogenic properties of miR-199b-5p and substantiated miR-199b-5p overexpression as a biomarker of subclinical CVD. The downregulation of miR-199b-5p by metformin confirmed its cardio-protective effect.

Monomeric C‑reactive protein level is associated with osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage degeneration and secondary bone hyperplasia. C-reactive protein (CRP) is an acute-phase protein that is widely used as a marker of inflammation. Elevated plasma levels of CRP are commonly observed in patients with OA during the acute phase. Current evidence indicates that CRP dissociating into a monomeric form (mCRP) is the main functional conformation at inflammatory loci. However, it remains unclear whether mCRP is associated with OA and whether mCRP can be used as a biomarker for its pathogenesis. In the present study, the concentration of CRP, mCRP and anti-mCRP autoantibody were detected by performing ELISA. The levels of plasma CRP, mCRP and anti-mCRP autoantibody between healthy subjects and patients with OA were compared. The results revealed that plasma mCRP was strongly associated with OA, while mCRP autoantibodies exhibited little correlation with this condition. Additionally, it was identified that the plasma mCRP levels in Kellgren-Lawrence (KL) grade 4 patients were significantly higher than in those with KL grade 3. Thus, it was revealed in the present study that plasma level of mCRP is associated with OA, which may directly reflect the disease degree of patients. Therefore, mCRP may be a potential indicator that can be used to monitor the disease activity and evaluate the efficiency of OA therapy.

The Complex Role of C-Reactive Protein in Systemic Lupus Erythematosus

C-reactive protein (CRP) is well-known as a sensitive albeit unspecific biomarker of inflammation. In most rheumatic conditions, the level of this evolutionarily highly conserved pattern recognition molecule conveys reliable information regarding the degree of ongoing inflammation, driven mainly by interleukin-6. However, the underlying causes of increased CRP levels are numerous, including both infections and malignancies. In addition, low to moderate increases in CRP predict subsequent cardiovascular events, often occurring years later, in patients with angina and in healthy individuals. However, autoimmune diseases characterized by the Type I interferon gene signature (e.g., systemic lupus erythematosus, primary Sjögren’s syndrome and inflammatory myopathies) represent exceptions to the general rule that the concentrations of CRP correlate with the extent and severity of inflammation. In fact, adequate levels of CRP can be beneficial in autoimmune conditions, in that they contribute to efficient clearance of cell remnants and immune complexes through complement activation/modulation, opsonization and phagocytosis. Furthermore, emerging data indicate that CRP constitutes an autoantigen in systemic lupus erythematosus. At the same time, the increased risks of cardiovascular and cerebrovascular diseases in patients diagnosed with systemic lupus erythematosus and rheumatoid arthritis are well-established, with significant impacts on quality of life, accrual of organ damage, and premature mortality. This review describes CRP-mediated biological effects and the regulation of CRP release in relation to aspects of cardiovascular disease and mechanisms of autoimmunity, with particular focus on systemic lupus erythematosus.

Monomeric C reactive protein (mCRP) regulates inflammatory responses in human and mouse chondrocytes

C-reactive protein (CRP) is an acute-phase protein that is used as an established biomarker to follow disease severity and progression in a plethora of inflammatory diseases. However, its pathophysiologic mechanisms of action are still poorly defined and remain elusive. CRP, in its pentameric form, exhibits weak anti-inflammatory activity. On the contrary, the monomeric isoform (mCRP) exhibits potent pro-inflammatory properties in endothelial cells, leukocytes, and platelets. So far, no data exists regarding mCRP effects in human or mouse chondrocytes. This work aimed to verify the pathophysiological relevance of mCRP in the etiology and/or progression of osteoarthritis (OA). We investigated the effects of mCRP in cultured human primary chondrocytes and in the chondrogenic ATDC5 mouse cell line. We determined mRNA and protein levels of relevant factors involved in inflammatory responses and the modulation of nitric oxide synthase type II (NOS2), an early inflammatory molecular target. We demonstrate, for the first time, that monomeric C reactive protein increases NOS2, COX2, MMP13, VCAM1, IL-6, IL-8, and LCN2 expression in human and murine chondrocytes. We also demonstrated that NF-kB is a key factor in the intracellular signaling of mCRP-driven induction of pro-inflammatory and catabolic mediators in chondrocytes. We concluded that mCRP exerts a sustained catabolic effect on human and murine chondrocytes, increasing the expression of inflammatory mediators and proteolytic enzymes, which can promote extracellular matrix (ECM) breakdown in healthy and OA cartilage. In addition, our results implicate the NF-kB signaling pathway in catabolic effects mediated by mCRP.

Purification of Recombinant Mouse C-Reactive Protein from Pichia Pastoris GS115 by Nickel Chelating Sepharose Fast-Flow Affinity Chromatography and P-Aminophenyl Phosphoryl Choline Agarose Resin Affinity Chromatography in Tandem

C-reactive protein (CRP) is a circulating marker of inflammation yet with ill-defined biological functions. This is partly due to the uncharacterized activities of endogenous CRP in mice, the major animal model used to define protein function. The hurdles for purification and characterization of mouse CRP are its low circulating levels and the lack of specific antibodies. To clear these hurdles, here we developed an efficient expression system by constructing recombinant Pichia pastoris cells for secretion of native conformation mouse CRP. The recombinant expression of mouse CRP in Escherichia coli failed to yield sufficient amount of native protein, reflecting the importance of post-translational modification of glycosylation in aiding proper folding. By contrast, sufficient amount of native mouse CRP was successfully purified from P. pastoris. Preliminary purification was performed by Nickel Chelating Sepharose Fast-Flow affinity chromatography with 6 × His tags attached to the protein. Subsequently, p-Aminophenyl Phosphoryl Choline Agarose resin affinity chromatography was used for tandem purification. The purified mouse CRP showed native pentamer and capabilities of PC binding. Moreover, the 6 × His tag provides a convenient tool for detecting the interactions of mouse CRP with ligands.

Update Advances on C-Reactive Protein in COVID-19 and Other Viral Infections

Severe coronavirus disease 2019 (COVID-19) can manifest as a viral-induced hyperinflammation with multiorgan dysfunction. It has been documented that severe COVID-19 is associated with higher levels of inflammatory mediators than a mild disease, and tracking these markers may allow early identification or even prediction of disease progression. It is well known that C-reactive protein (CRP) is the acute-phase protein and the active regulator of host innate immunity, which is highly predictive of the need for mechanical ventilation and may guide escalation of treatment of COVID-19-related uncontrolled inflammation. There are numerous causes of an elevated CRP, including acute and chronic responses, and these can be infectious or non-infectious in etiology. CRP are normally lacking in viral infections, while adaptive immunity appears to be essential for COVID-19 virus clearance, and the macrophage activation syndrome may explain the high serum CRP contents and contribute to the disease progression. Nevertheless, for the assessment of host inflammatory status and identification of viral infection in other pathologies, such as bacterial sepsis, the acute-phase proteins, including CRP and procalcitonin, can provide more important information for guiding clinical diagnosis and antibiotic therapy. This review is aimed to highlight the current and most recent studies with regard to the clinical significance of CRP in severe COVID-19 and other viral associated illnesses, including update advances on the implication of CRP and its form specifically on the pathogenesis of these diseases. The progressive understanding in these areas may be translated into promising measures to prevent severe outcomes and mitigate appropriate treatment modalities in critical COVID-19 and other viral infections.

Intra-subunit Disulfide Determines the Conversion and Structural Stability of CRP Isoforms

C-reactive protein (CRP) is a major human acute-phase reactant that is composed of five identical subunits. CRP dissociates into subunits at inflammatory loci forming monomeric CRP (mCRP) with substantially enhanced activities, which can be further activated by reducing the intra-subunit disulfide bond. However, conformational changes underlying the activation process of CRP are less well understood. Conformational changes accompanying the conversion of CRP to mCRP with or without reduction were examined with circular dichroism spectroscopy, fluorescence spectroscopy, electron microscopy, size-exclusion chromatography, and neoepitope expression. The conversion of CRP to mCRP follows a two-stage process. In the first stage, CRP dissociates into molten globular subunits characterized by intact secondary structure elements with greatly impaired tertiary packing. In the second stage, these intermediates completely lose their native subunit conformation and assemble into high-order aggregates. The inclusion of reductant accelerates the formation of molten globular subunits in the first step and promotes the formation of more compact aggregates in the second stage. We further show a significant contribution of electrostatic interactions to the stabilization of native CRP. The conformational features of dissociated subunits and the aggregation of mCRP may have a key impact on their activities.

Monomeric C-reactive protein regulates fibronectin mediated monocyte adhesion

The acute phase reactant C-reactive protein (CRP) binds with high affinity to fibronectin (FN), but this binding occurs only at pH 6.5 or lower, and the binding is inhibited by calcium ions at physiological pH. Since CRP in the circulating blood exists in a calcium-binding form, the interaction between CRP and FN in vivo has been uncertain. CRP can undergo a conformational rearrangement in the absence of calcium or in the local microenvironment (e.g., acidic pH) of inflamed tissue to dissociate into monomeric CRP (mCRP). Therefore, we tested whether these discrepancies can be explained by the different isoforms and locations of CRP. Surface plasmon resonance and ELISA assays showed that mCRP binds with high affinity to FN, and the binding of mCRP to FN was unaffected by calcium or pH. Peptide competition assay, deletion mutant binding assay and protein docking analyse verified that the binding site of mCRP to FN is residues a.a.35-47. Furthermore, mCRP can significantly enhance the adhesion of monocytes to FN as well as upregulate the adhesion molecules expression on endothelial cell. Colocalization of mCRP with FN was observed in mice with DSS-induced colitis, whereas there was very little signal orcolocalization of CRP. These results provide in vitro and in vivo evidence that mCRP formed by local dissociation from circulating CRP is the major isoform that interacts with FN and regulates FN-mediated monocyte adhesion, which is involved in the pro-inflammatory process.

Lignans' Potential in Pre and Post-onset Type 2 Diabetes Management

INTRODUCTION

Type 2 Diabetes (T2D) cases continue to rise dramatically despite efforts to get people to exercise and eat with a view to health and combatting the cluster of 7 issues (central obesity (elevated waist circumference), hyperglycaemia, hypertension, dyslipidemia, pro-thrombotic state, increased oxidation (including Low-density Lipoprotein (LDL)) and the pro-inflammatory state associated with pre- and post-onset T2D.

BACKGROUND

There are numerous medications available to deal with these seven major issues. However, each medication currently available manages a maximum of two cluster members at a time. Consequently, polypharmacy is frequently required to manage the cluster of seven. Polypharmacy brings with it high financial costs for numerous medications, the risk of poor compliance (particularly so in older patients), side effects and drug interactions. Thus, there is a search for new agents that reduce the high costs and risks of polypharmacy while at the same time combatting three or more of the cluster of seven. There is very limited evidence to suggest that one or more lignans may efficaciously and safely, in the short and long term, manage at least three of the cluster of seven, pre- and post-T2D onset, thus reducing polypharmacy. However, multi-centre, large clinical trials are required before any definitive conclusions about these lignans can be reached regarding their safe and efficacious polypharmacy reduction potential, both long and short-term, in pre and post-onset T2D management.

CONCLUSION

It is concluded that some lignans appear to have the potential to manage at least three members of the cluster of seven in pre- or post-T2D onset and hence reduce polypharmacy but much more investigation is required to confirm if such is the case. At the moment, there is not enough evidence that any of the lignans will, in the long or short term, safely and efficaciously manage the cluster of seven via polypharmacy reduction.

The Clinical Significance and Potential Role of C-Reactive Protein in Chronic Inflammatory and Neurodegenerative Diseases

C-reactive protein (CRP) is an acute-phase protein synthesized by hepatocytes in response to pro-inflammatory cytokines during inflammatory/infectious processes. CRP exists in conformationally distinct forms such as the native pentameric CRP and monomeric CRP (mCRP) and may bind to distinct receptors and lipid rafts and exhibit different functional properties. It is known as a biomarker of acute inflammation, but many large-scale prospective studies demonstrate that CRP is also known to be associated with chronic inflammation. This review is focused on discussing the clinical significance of CRP in chronic inflammatory and neurodegenerative diseases, such as cardiovascular disease, type 2 diabetes mellitus, age-related macular degeneration, hemorrhagic stroke, Alzheimer’s disease, and Parkinson’s disease, including recent advances on the implication of CRP and its forms specifically on the pathogenesis of these diseases. Overall, we highlight the advances in these areas that may be translated into promising measures for the diagnosis and treatment of inflammatory diseases.

Structure and functionalities of the human c-reactive protein compared to the zebrafish multigene family of c-reactive-like proteins

Because of the recent discovery of multiple c-reactive protein (crp)-like genes in zebrafish (Danio rerio) with predicted heterogeneous phospholipid-binding amino acid sequences and heterogeneous transcript expression levels in viral survivors and adaptive-deficient mutants, zebrafish constitute an attractive new model for exploring the evolution of these protein's functions, including their possible participation in fish trained immunity. Circulating human CRP belongs to the short pentraxin family of oligomeric proteins that are characteristic of early acute-phase innate responses and is widely used as a clinical inflammation marker. In contrast to pentameric human CRP (pCRP), zebrafish CRPs are trimeric (tCRP); however monomeric CRP (mCRP) conformations may also be generated when associated with cellular membranes as occurs in humans. Compared to human CRP, zebrafish CRP-like proteins show homologous amino acid sequence stretches that are consistent with, although not yet demonstrated, cysteine-dependent redox switches, calcium-binding spots, phosphocholine-binding pockets, C1q-binding domains, regions interacting with immunoglobulin Fc receptors (FcR), unique mCRP epitopes, mCRP binding peptides to cholesterol-enriched rafts, protease target sites, and/or binding sites to monocyte, macrophage, neutrophils, platelets and/or endothelial cells. Amino acid variations among the zebrafish CRP-like multiprotein family and derived isoforms in these stretches suggest that functional heterogeneity best fits the wide variety of aquatic pathogens. As occurs in humans, phospholipid-tagged tCRP-like multiproteins might also influence local inflammation and induce innate immune responses; however, in addition, different zebrafish tCRP-like proteins and/or isoforms might fine tune new still unknown functions. The information reviewed here could be of value for future studies not only to comparative but also medical immunologists and/or fisheries sectors. This review also introduces some novel speculations for future studies.

Fc Gamma Receptor IIA (CD32A) R131 Polymorphism as a Marker of Genetic Susceptibility to Sepsis

Sepsis is a devastating disease that can affect humans at any time between neonates and the elderly and is associated with mortality rates that range from 30 to 80%. Despite intensive efforts, its treatment has remained the same over the last few decades. Fc receptors regulate multiple immune responses and have been investigated in diverse complex diseases. FcγRIIA (CD32A) is an immunoreceptor, tyrosine-based activation motif-bearing receptor that binds immunoglobulin G and C-reactive protein, important opsonins in host defense. We conducted a study of 702 patients (184 healthy individuals, 171 non-infected critically ill patients, and 347 sepsis patients) to investigate if genetic polymorphisms in the CD32A coding region affect the risk of septic shock. All individuals were genotyped for a variant at position 131 of the FcγRIIA gene. We found that allele G, associated with the R131 genotype, was significantly more frequent in septic patients than in the other groups (p = 0.05). Our data indicate that FcγRIIA genotyping can be used as a marker of genetic susceptibility to sepsis.

The functional activities of complement factor H are impaired in patients with ANCA-positive vasculitis

Increasing evidences have demonstrated that the activation of the alternative complement pathway is crucial for the pathogenesis of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV). Our recent study found that circulating levels of complement factor H (FH), a key regulator of the alternative pathway, were associated with disease activity. In the current study, functional activities of FH were assessed to further explore the potential role of FH in the pathogenesis of AAV. We found that the two patients with ANCA-negative pauci-immune necrotizing crescentic glomerulonephritis exhibited relatively normal functional activities of FH. However, patients with ANCA-positive vasculitis exhibited deficient functional activities of FH, in terms of interaction with and the regulation of C3b, binding to mCRP and endothelial cells, and the protection of host cells against complement attack. Our findings indicate that functional activities of FH are deficient in patients with ANCA-positive vasculitis, potentially contributing to the disease development.

C-reactive protein and inflammation: conformational changes affect function

The prototypic acute-phase reactant C-reactive protein (CRP) has long been recognized as a useful marker and gauge of inflammation. CRP also plays an important role in host defense against invading pathogens as well as in inflammation. CRP consists of five identical subunits arranged as a cyclic pentamer. CRP exists in at least two conformationally distinct forms, i.e. native pentameric CRP (pCRP) and modified/monomeric CRP (mCRP). These isoforms bind to distinct receptors and lipid rafts, and exhibit distinct functional properties. Dissociation of pCRP into its subunits occurs within the inflammatory microenvironment and newly formed mCRP may then contribute to localizing the inflammatory response. Accumulating evidence indicates that pCRP possesses both pro- and anti-inflammatory actions in a context-dependent manner, whereas mCRP exerts potent pro-inflammatory actions on endothelial cells, endothelial progenitor cells, leukocytes and platelets, and thus may amplify inflammation. Here, we review recent advances that may explain how conformational changes in CRP contribute to shaping the inflammatory response and discuss CRP isomers as potential therapeutic targets to dampen inflammation.

Interaction of SNP in the CRP gene and plasma fatty acid profile in inflammatory pattern: A cross-sectional population-based study

OBJECTIVE

To assess the interaction of three single nucleotide polymorphisms in the C-reactive protein (CRP) gene and plasma fatty acid (FA) levels in modulating inflammatory profile.

METHODS

A total of 262 subjects, aged >19 y and <60 y, participated in a cross-sectional, population-based study performed in Brazil. Three single nucleotide polymorphisms (rs1205, rs1417938, and rs2808630) spanning the CRP gene were genotyped. Eleven plasma inflammatory biomarkers and plasma FA profile were determined. Cluster analysis was performed to stratify individuals based on eleven inflammatory biomarkers into two groups: an inflammatory (INF) and a noninflammatory group.

RESULTS

The INF cluster had higher age, waist circumference, systolic blood pressure, and diastolic blood pressure; higher levels of triacylglycerol, high-sensitivity CRP, tumor necrosis factor-α, interleukin (IL)-8, IL-6, IL-1β, IL-12, IL-10, soluble monocyte chemoattractant protein-1, soluble intercellular adhesion molecule-1, C16:0, polyunsaturated fatty acid, and omega (n)-6 polyunsaturated fatty acid; and greater C20:4n-6, C18:1/18:0, and C20:4/20:3 ratios than the noninflammatory group. Statistically significant gene-plasma C16:1n-7 interaction was detected for rs1417938 (P = 0.047). Those with a dominant homozygous rs2808630 had a lower risk of belonging to the INF group with the upper 50th percentile of C20:4n-6, n-3 highly unsaturated FA, and C20:4/20:3 ratio. Regarding rs1205, A allele carriers had lower risk of being in the INF group when C20:5n-3 and n-3 highly unsaturated FA levels were greater than the median.

CONCLUSIONS

The INF group exhibited changes in metabolic parameters that predispose this group to chronic disease, where polymorphisms in the CRP gene modulated the risk of being in the INF group depending on individual plasma fatty acid and lipid profile.

Effect of omega-3 supplementation on inflammatory parameters in patients on chronic ambulatory peritoneal dialysis

Background:

End stage renal disease (ESRD) is a state of micro inflammation that attenuates patient's life span and quality of life. Inflammatory markers like interlukin 6 (IL-6) and C- reactive protein (CRP) can predict inflammatory state in ESRD patients. Dietary limitations are risk factors for omega-3 deficiency in these patients. Omega-3 supplementation is an attractive material that proposed in inflammation modulation. The aim of this study is evaluation of effect of omega-3 supplementation on IL-6 and CRP level in chronic ambulatory peritoneal dialysis (CAPD) patients.

Materials and Methods:

This randomized controlled double-blind clinical trial is performed in 40 CAPD patients in two academic hospitals in Isfahan, Iran. One group received 1000 mg omega-3 capsule (each capsule contains 180 mg Eicosapentanoic and 120 mg Dosahexanoic acid) three times a day orally for 8 weeks (n = 20) and the other matched group by placebo (n = 20). Serum level of IL-6 and quantitative CRP (Q-CRP) were measured in beginning and the end of the study. Finally all data were analyzed by SPSS version 18.

Results:

Mean age of patients was 53 years old in omega-3 group patients and 54 years old in placebo group. There were not any differences in CRP and IL-6 level in the beginning and the end of study between two groups (P: 0.81 and 0.10 for CRP and 0.26 and 0.23 for IL-6, respectively).

Conclusion:

Omega-3 supplementation did not effect on inflammatory markers (Q-CRP and IL-6) in CAPD patients after 8 weeks.

Solubilization and purification of recombinant modified C-reactive protein from inclusion bodies using reversible anhydride modification

The precise function of C-reactive protein (CRP) as a regulator of inflammation in health and disease continues to evolve. The true understanding of its role in host defense responses has been hampered by numerous reports of comparable systems with contradictory interpretations of CRP as a stimulator, suppressor, or benign contributor to such processes. These discrepancies may be explained in part by the existence of a naturally occurring CRP isoform, termed modified CRP (i.e., mCRP), that is expressed when CRP subunits are dissociated into monomeric structures. The free mCRP subunit undergoes a non-proteolytic conformational change that has unique solubility, antigenicity, and bioactivity compared to the subunits that remain associated in the native, pentameric CRP molecule (i.e., pCRP). As specific reagents have been developed to identify and quantify mCRP, it has become apparent that this isoform can be formed spontaneously in calcium-free solutions. Furthermore, mCRP can be expressed on perturbed cell membranes with as little as 24–48 h incubation in tissue culture. Because mCRP has the same size as pCRP subunits as evaluated by SDS-PAGE, its presence in a pCRP reagent would not be apparent using this technique to evaluate purity. Finally, because many antibody reagents purported to be specific for “CRP” contains some, or substantial specificity to mCRP, antigen-detection techniques using such reagents may fail to distinguish the specific CRP isoform detected. All these caveats concerning CRP structures and measurements suggest that the aforementioned contradictory studies may reflect to some extent on distinctive bioactivities of mCRP rather than on pCRP. To provide a reliable, abundant supply of mCRP for separate and comparable studies, a recombinant protein was engineered and expressed in E. coli (i.e., recombinant mCRP or r_mCRP). Synthesized protein was produced as inclusion bodies which proved difficult to solubilize for purification and characterization. Herein, we describe a method using anhydride reagents to effectively solubilize r_mCRP and allow for chromatographic purification in high yield and free of contaminating endotoxin. Furthermore, the purified r_mCRP reagent represents an excellent comparable protein to the biologically produced mCRP and as a distinctive reagent from pCRP. Deciphering the true function of CRP in both health and disease requires a knowledge, understanding, and reliable supply of each of its structures so to define the distinctive effects of each on the body’s response to tissue damaging events.

Complement activation and choriocapillaris loss in early AMD: implications for pathophysiology and therapy

Age-related macular degeneration (AMD) is a common and devastating disease that can result in severe visual dysfunction. Over the last decade, great progress has been made in identifying genetic variants that contribute to AMD, many of which lie in genes involved in the complement cascade. In this review we discuss the significance of complement activation in AMD, particularly with respect to the formation of the membrane attack complex in the aging choriocapillaris. We review the clinical, histological and biochemical data that indicate that vascular loss in the choroid occurs very early in the pathogenesis of AMD, and discuss the potential impact of vascular dropout on the retinal pigment epithelium, Bruch's membrane and the photoreceptor cells. Finally, we present a hypothesis for the pathogenesis of early AMD and consider the implications of this model on the development of new therapies.

Mutations of C-reactive protein (CRP) -286 SNP, APC and p53 in colorectal cancer: implication for a CRP-Wnt crosstalk

C-reactive protein (CRP) is an established marker of inflammation with pattern-recognition receptor-like activities. Despite the close association of the serum level of CRP with the risk and prognosis of several types of cancer, it remains elusive whether CRP contributes directly to tumorigenesis or just represents a bystander marker. We have recently identified recurrent mutations at the SNP position -286 (rs3091244) in the promoter of CRP gene in several tumor types, instead suggesting that locally produced CRP is a potential driver of tumorigenesis. However, it is unknown whether the -286 site is the sole SNP position of CRP gene targeted for mutation and whether there is any association between CRP SNP mutations and other frequently mutated genes in tumors. Herein, we have examined the genotypes of three common CRP non-coding SNPs (rs7553007, rs1205, rs3093077) in tumor/normal sample pairs of 5 cancer types (n = 141). No recurrent somatic mutations are found at these SNP positions, indicating that the -286 SNP mutations are preferentially selected during the development of cancer. Further analysis reveals that the -286 SNP mutations of CRP tend to co-occur with mutated APC particularly in rectal cancer (p = 0.04; n = 67). By contrast, mutations of CRP and p53 or K-ras appear to be unrelated. There results thus underscore the functional importance of the -286 mutation of CRP in tumorigenesis and imply an interaction between CRP and Wnt signaling pathway.

C-reactive protein-derived peptide 201-206 inhibits neutrophil adhesion to endothelial cells and platelets through CD32

The role of CRP as a regulator of inflammation is not fully understood. Structural rearrangement in CRP results in expression of potent proinflammatory actions. Proteolysis of CRP yields the C-terminal peptide Lys(201)-Pro-Gln-Leu-Trp-Pro(206). Here, we investigated the impact of this peptide on neutrophil interactions with endothelial cells and platelets, critical inflammatory events triggering acute coronary artery disease. CRP peptide 201-206 induced L-selectin shedding from human neutrophils and inhibited L-selectin-mediated neutrophil adhesion to TNF-α-activated HCAECs under nonstatic conditions. CRP peptide 201-206 also attenuated shear-induced up-regulation of platelet P-selectin expression, platelet capture of neutrophils, and subsequent homotypic neutrophil adhesion in human whole blood. Anti-CD32 but not anti-CD16 or anti-CD64 mAb effectively prevented the inhibitory actions of CRP peptide 201-206. Substitution of Lys(201), Gln(203), or Trp(205) with Ala in CRP peptide 201-206 resulted in loss of the biological activities, whereas peptides in which Pro(202), Leu(204), or Pro(206) was substituted with Ala retained biological activity. We identified amino acid residues involved in CRP peptide 201-206-FcγRII (CD32) interactions, which mediate potent antineutrophil and antiplatelet adhesion actions, and these findings open up new perspectives for limiting inflammation and thrombosis underlying coronary artery disease.

Opposing effects of monomeric and pentameric C-reactive protein on endothelial progenitor cells

C-reactive protein (CRP) has been linked to the pathogenesis of atherosclerosis. The dissociation of native, pentameric (p)CRP to monomeric (m)CRP on the cell membrane of activated platelets has recently been demonstrated. The dissociation of pCRP to mCRP may explain local pro-inflammatory reactions at the site of developing atherosclerotic plaques. As a biomarker, pCRP predicts cardiovascular adverse events and so do reduced levels and function of circulating endothelial progenitor cells (EPCs). We hypothesised that mCRP and pCRP exert a differential effect on EPC function and differentiation. EPCs were treated with mCRP or pCRP for 72 h, respectively. Phenotypical characterisation was done by flow cytometry and immunofluorescence microscopy, while the effect of mCRP and pCRP on gene expression was examined by whole-genome gene expression analysis. The functional capacity of EPCs was determined by colony forming unit (CFU) assay and endothelial tube formation assay. Double staining for acetylated LDL and ulex lectin significantly decreased in cells treated with pCRP. The length of tubuli in a matrigel assay with HUVECs decreased significantly in response to pCRP, but not to mCRP. The number of CFUs increased after pCRP treatment. RNA expression profiling demonstrated that mCRP and pCRP cause highly contradictory gene regulation. Interferon-responsive genes (IFI44L, IFI44, IFI27, IFI 6, MX1, OAS2) were among the highly up-regulated genes after mCRP, but not after pCRP treatment. In conclusion, EPC phenotype, genotype and function were differentially affected by mCRP and pCRP, strongly arguing for differential roles of these two CRP conformations. The up-regulation of interferon-inducible genes in response to mCRP may constitute a mechanism for the local regulation of EPC function.

Monomeric C-reactive protein is prothrombotic and dissociates from circulating pentameric C-reactive protein on adhered activated platelets under flow

AIMS

We previously reported that C-reactive protein bioactivity on thrombogenesis was based on loss of its pentameric symmetry, resulting in formation of monomeric C-reactive protein. Our purpose was to provide mechanistic information on the direct effects of C-reactive protein isoforms on platelet activation and provide a C-reactive protein dissociation mechanism in circulating blood.

METHODS AND RESULTS

C-reactive protein-induced platelet activation was evaluated by flow cytometry. Platelet aggregation, clot properties, and coagulation were also measured. Washed platelets were incubated with C-reactive protein isoforms and vasodilator-stimulated phosphoprotein (VASP) phosphorylation was analysed by western blot and immunofluorescence. C-reactive protein dissociation under flow was evaluated by confocal microscopy on the surface of adhered platelets after perfusing human blood containing pentameric C-reactive protein at different shear rates. Dissociated monomeric C-reactive protein thrombogenicity was measured in flow experiments. Platelet aggregation and flow cytometry analysis revealed that monomeric C-reactive protein significantly induced platelet aggregation, surface P-selectin and CD63 exposure, and glycoprotein IIb-IIIa activation, whereas pentameric C-reactive protein was unable to produce any effect. p38 mitogen-activated protein kinase (MAPK) and Jun N-terminal kinase (JNK) inhibitors, as well as CD36 blocking antibody partially inhibited monomeric C-reactive protein-induced platelet activation and aggregation. Additionally, monomeric C-reactive protein significantly induced VASP dephosphorylation at serine 239. We found that pentameric C-reactive protein dissociated into monomeric C-reactive protein on the surface of activated adhered platelets under flow conditions and that this generated monomeric C-reactive protein promoted further platelet recruitment.

CONCLUSIONS

These data indicate that whereas serum pentameric C-reactive protein may not affect platelet activation, monomeric C-reactive protein, which dissociates from pentameric C-reactive protein on the surface of activated platelets, could contribute to atherothrombotic complications by promoting thrombosis.

Platelet activation, coagulation activation and C-reactive protein in simultaneous samples from the vascular access and peripheral veins of haemodialysis patients

INTRODUCTION

Most studies of haemodialysis (HD) patients compare venous blood samples from controls with samples from the vascular access (VA) of HD patients. We hypothesised that VA samples may be more prothrombotic compared with venous samples.

METHODS

Samples were taken simultaneously from the VA and the contralateral antecubital vein, from 26 patients immediately before HD. Platelet function was assessed by (1) flow cytometric measurement of P-selectin expression and fibrinogen binding (±ADP) and 2) Ultegra rapid platelet function assay. Plasma soluble P-selectin, von Willebrand factor antigen, high sensitivity C-reactive Protein (hs-CRP), thrombin-antithrombin III complex and D-dimer measured by ELISA.

RESULTS

Thrombin receptor activating peptide-induced platelet aggregation (P < 0.001) and hs-CRP (P < 0.001) were higher in VA compared with venous samples. Unstimulated platelet fibrinogen binding (P = 0.016) and ADP-stimulated P-selectin expression (P = 0.008) were lower in VA compared with venous samples. The significant difference in hsCRP persisted when patients taking and not taking antiplatelet therapy were analysed separately, but platelet activation remained significantly different only in the nonantiplatelet group.

CONCLUSION

There are statistically significant differences between sampling sites, although samples from the VA do not appear to be more pro-thrombotic. Future studies comparing HD patients with controls should ensure uniformity of sampling sites to prevent inaccurate conclusions being drawn.

The relation between Lp-PLA2 levels with periodic limb movements

OBJECTIVE

Lipoprotein-associated phospholipase A2 (Lp-PLA2), a novel marker of vulnerable plaque to prone rupture, is a predictor of both cardiovascular event and cerebrovascular event, and highly sensitive-C-reactive protein (hs-CRP) is an acute-phase response protein implicated in a broad range of cardiovascular diseases. We aimed to examine the association between periodic limb movements in sleep (PLMs) with circulating Lp-PLA2 and hs-CRP levels in patients with PLMs.

METHODS

Seventy patients with newly diagnosed PLM with polysomnography were enrolled this study. Patients were divided into two groups according to PLM index (normal PLM index, <15; elevated PLM index, ≥15). Lp-PLA2 and hs-CRP concentrations were measured in serum samples by turbidimetric and nephelometric methods, respectively. The concentrations of these parameters were compared between two groups and correlation analysis was performed between PLMs and Lp-PLA2 and hs-CRP levels.

RESULTS

Lp-PLA2 levels and hs-CRP were significantly increased in elevated PLM index group compared with the control group (206.8 ± 78.1 vs 157.8 ± 56.7, p = 0.003, and 4.2 ± 3.5 vs 2.4 ± 2.1, p = 0.02, respectively). PLM index was positively correlated with Lp-PLA2 levels (r = 0.40, p = 0.001) and hs-CRP (r = 0.24, p = 0.05). In the linear regression model, Lp-PLA2 was an independent predictor of PLM index (R(2) = 0.36, p = 0.005).

CONCLUSION

This study demonstrated an independent linear relation between PLM index and Lp-PLA2. In addition, it was seen increased Lp-PLA2 and hs-CRP levels in patients with elevated PLM index. Based on these results, we can suggest that risk of vascular events may be increased in patients with PLMs and with increased PLM index.

Study of the interaction of the C-reactive protein monomer with the U937 monocyte

C-reactive protein (CRP) has two structurally distinct isoforms, the CRP pentamer and the CRP monomer. A role for the CRP monomer in atherosclerosis is emerging, but the underlying mechanisms are only beginning to be understood. Monocytes are an important contributor to atherosclerosis, and foam cell formation is the hallmark of atherogenesis. However, whether the CRP monomer can directly interact with the monocytes and modulate their responses remains unknown. Furthermore, although FcgammaRIII (CD16) has been identified as the receptor for the CRP monomer on neutrophils, its role in mediating the CRP monomer's biological effects in other cell types has been questioned. In this study, we investigated the interaction of the CRP monomer with the monocytes using the U937 monocytic cell line. The CRP monomer specifically binds to U937 cells. This binding is unique in that it is independent of FcgammaRs and insensitive to protease digestion of the cell surface proteins. Further assays revealed that the CRP monomer directly incorporates into the plasma membrane. Interestingly, the presence of the CRP monomer efficiently retards oxidized low-density lipoprotein-induced foam cell formation of PMA-differentiated U937 macrophages and peripheral blood monocytic cell-derived macrophages. These findings provide additional evidence for the notion that the CRP monomer is an active CRP isoform that plays a role in atherogenesis via the direct modulation of the behavior of the monocytes.

Monomeric CRP contributes to complement control in fluid phase and on cellular surfaces and increases phagocytosis by recruiting factor H

Complement forms the first defense line of innate immunity and has an important role in the non-inflammatory clearance of apoptotic and necrotic cells. Factor H is one essential complement inhibitor that binds to the acute phase reactant C-reactive protein (CRP). By using recombinant proteins, calcium-independent binding of Factor H to monomeric CRP (mCRP), but not to pentameric CRP (pCRP), was shown. In addition to the two known CRP-binding sites, a novel third site was localized within the C-terminus. This region is frequently mutated in the hemolytic uremic syndrome and the mutant proteins show reduced mCRP binding. In this study, we show that mCRP directs Factor H to the surface of apoptotic and necrotic endothelial cells and identify phosphocholine as one binding moiety for this complex. Factor H-mCRP complexes enhance C3b inactivation both in the fluid phase and on the surface of damaged cells and inhibit the production of pro-inflammatory cytokines. By recruiting the soluble complement inhibitor Factor H to the surface of damaged cells, mCRP blocks the progression of the complement cascade beyond the step of the C3 convertase, prevents the formation of inflammatory activation products, and thus contributes to the safe removal of opsonized damaged cells and particles.

Binding of the monomeric form of C-reactive protein to enzymatically-modified low-density lipoprotein: effects of phosphoethanolamine

BACKGROUND

The 5 subunits of native pentameric C-reactive protein (CRP) are dissociated to generate the monomeric form of CRP (mCRP) in some in vitro conditions, both physiological and non-physiological, and also in vivo. Many bioactivities of mCRP generated by urea-treatment of CRP and of mCRP generated by mutating the primary structure of CRP have been reported. The bioactivities of mCRP generated by spontaneous dissociation of CRP are largely unexplored.

METHODS

We purified mCRP generated by spontaneous dissociation of CRP and investigated the binding of mCRP to enzymatically-modified low-density lipoprotein (E-LDL).

RESULTS

mCRP was approximately 60 times more potent than CRP in binding to E-LDL. In the presence of the small-molecule compound phosphoethanolamine (PEt), at 37 degrees C, the binding of mCRP to E-LDL was enhanced <2-fold, while the binding of CRP to E-LDL was enhanced >10-fold. In contrast, PEt inhibited the binding of both CRP and mCRP to pneumococcal C-polysaccharide, another phosphocholine-containing ligand to which CRP and mCRP were found to bind. We have not investigated yet whether PEt alters the structure of CRP at 37 degrees C.

CONCLUSIONS

Combined data suggest that the targeting of CRP with the aim to monomerize CRP in vivo may be an effective approach to capture modified forms of LDL.

Diurnal variability of C-reactive protein in obstructive sleep apnea

OBJECTIVE

The objective of this study is to examine the diurnal variability of C-reactive protein (CRP) in obstructive sleep apnea (OSA).

METHODS AND MEASUREMENTS

Participants included 44 women and men with untreated OSA (mean apnea/hypopnea index = 37.5, SD +/- 28) and 23 healthy adults with no OSA. Sleep was monitored with polysomnography in the University of California San Diego General Clinical Research Center. Over a 24-h period, blood was collected every 2 h, and CRP levels were determined.

RESULTS

Adjusting for age, gender, and body mass index, a significant group by time interaction showed that patients with OSA had higher CRP levels during the daytime (8:00 a.m.-8:00 p.m.) versus the nighttime (10:00 p.m. until 6:00 p.m.; p < 0.001). Non-apneics showed no significant change in CRP levels during the 24 h.

CONCLUSIONS

The findings indicate that sleep apnea patients have disproportionately elevated CRP levels in the day versus the nighttime, possibly as a result of carryover effects of nighttime arousal into the daytime.

Altered plasma adipokines and markers of oxidative stress suggest increased risk of cardiovascular disease in First Nation youth with obesity or type 2 diabetes mellitus

OBJECTIVE

To evaluate cardiovascular disease risk in First Nation youth with and without type 2 diabetes mellitus (T2DM) or obesity by comparing pro- and anti-inflammatory adipokines, markers of oxidative stress and the plasma phospholipid fatty acid profile.

METHOD

Self-declared First Nation youth (12-15 yr) with T2DM (n = 24) as well as age-, gender-, and body mass index-matched controls (obese group; n = 19) and unmatched controls (control group; n = 34) were recruited from a pediatric diabetes clinic.

RESULTS

Plasma tumor necrosis factor-alpha, ultrasensitive C-reactive protein, resistin, and total antioxidant status were not different among the three groups. Plasma total leptin, soluble leptin receptor, and free leptin were significantly higher in the T2DM group than the control group (p < 0.001, p = 0.019, p < 0.001, respectively) but did not differ from the obese group. Similarly, oxidized low-density lipoprotein was higher in the T2DM group compared with controls (p = 0.002) but not in the obese group. However, interleukin-6 was significantly higher (p < 0.001) in the T2DM group compared with both the control and the obese groups, suggesting that T2DM, but not an increase in adiposity, was responsible for this elevation. Adiponectin was significantly lower in the T2DM group compared with the control group only (p = 0.035).

CONCLUSIONS

Changes in plasma adipokines and oxidative stress can already be detected in youth with T2DM; however, many of the changes are mirrored in obese youth, suggesting that both these populations are at an increased risk for future cardiovascular complications.

The connection between C-reactive protein and atherosclerosis

The connection between C-reactive protein (CRP) and atherosclerosis lies on three grounds. First, the concentration of CRP in the serum, which is measured by using highly sensitive (a.k.a. 'hs') techniques, correlates with the occurrence of cardiovascular disease. Second, although CRP binds only to Fcgamma receptor-bearing cells and, in general, to apoptotic and damaged cells, almost every type of cultured mammalian cells has been shown to respond to CRP treatment. Many of these responses indicate proatherogenic functions of CRP but are being reinvestigated using CRP preparations that are free of endotoxins, sodium azide, and biologically active peptides derived from the protein itself. Third, CRP binds to modified forms of low-density lipoprotein (LDL), and, when aggregated, CRP can bind to native LDL as well. Accordingly, CRP is seen with LDL and damaged cells at the atherosclerotic lesions and myocardial infarcts. In experimental rats, human CRP was found to increase the infarct size, an effect that could be abrogated by blocking CRP-mediated complement activation. In the Apob (100/100) Ldlr (-/-) murine model of atherosclerosis, human CRP was shown to be atheroprotective, and the importance of CRP-LDL interactions in this protection was noted. Despite all this, at the end, the question whether CRP can protect humans from developing atherosclerosis remains unanswered.

Conduct unbecoming: C-reactive protein interactions with a broad range of protein molecules

BACKGROUND

C-reactive protein (CRP), a pentamer composed of five identical 23-kd subunits, is a member of a highly conserved family of proteins known as pentraxins. CRP has been recognized as a risk factor for the development of both the native and transplant-associated forms of atherosclerosis. Understanding the biology of CRP may be relevant to understanding atherosclerosis development and progression.

METHODS

Using Western-blotting techniques, we examined the interactions between native, monomeric and mutationally and chemically modified CRP and a variety of antibodies, monoclonal and polyclonal.

RESULTS

CRP in its denatured monomeric form, but not in its native pentameric conformation, associates promiscuously with IgG molecules, including normal human IgG, as well as with a number of other proteins. This behavior is intrinsic to CRP and is not noted with other pentraxins such as serum amyloid P component or the long pentraxin, PTX3. Monomeric CRP co-localizes with vitronectin in human heart tissue sections.

CONCLUSIONS

We present these findings as cautionary advice, to indicate that characterization of monomeric CRP can be complicated by the propensity of the molecule to interact with a variety of immunoglobulins and other proteins. We also suggest that it is possible that such interactions could serve to eliminate excess of monomeric CRP and/or to scavenge altered, damaged and denatured proteins. These reactivities may be part of a regulatory mechanism to limit inflammation in the arterial wall.

Native C-reactive protein induces endothelial dysfunction in ApoE-/- mice: implications for iNOS and reactive oxygen species

OBJECTIVE

In addition to being a risk marker for cardiovascular disease, recent data suggests that C-reactive protein (CRP) induces endothelial dysfunction and promotes oxidative stress. We evaluated the effects of two conformers of CRP (pentameric, or native [nCRP], versus monomeric, or modified [mCRP]) on vessel function and production of reactive oxygen species (ROS) in an in-vivo model of atherosclerosis.

METHODS AND RESULTS

Female ApoE(-/-) mice, fed a "western-type" diet, were treated with either human nCRP or mCRP (2.5mg/kg s.c., weekly) or saline for 8 weeks. Endothelium-dependent and endothelium-independent vascular functions were assessed in isolated aortic rings under isometric conditions. Production of ROS in aortic rings was measured by electron spin resonance (ESR). Endothelium-dependent relaxation was impaired in nCRP-treated but not in mCRP-treated ApoE(-/-) mice. This impairment was reversed by preincubation with an inhibitor of inducible nitric oxide synthase (iNOS). Endothelium-independent relaxation, and iNOS and endothelial NOS (eNOS) protein expressions were similar among all groups. ESR experiments revealed lesser amounts of superoxide in the nCRP group as compared to the saline group, which is consistent with an increased transformation of NO to peroxynitrite.

CONCLUSIONS

nCRP can facilitate cardiovascular disease through impairment of endothelium-dependent vasoreactivity, in a manner that involves increased iNOS activity and a potential for increased peroxynitrite formation.

Periodontal disease severity is related to high levels of C-reactive protein in pre-eclampsia

OBJECTIVE

Recent studies have shown that pre-eclamptic women present a high prevalence of periodontitis, suggesting that active periodontal disease may play a role in the pathogenesis of pre-eclampsia. The present study analysed the effect of periodontal disease in the concentrations of serum high-sensitivity C-reactive protein (hs-CRP), and its association with pre-eclampsia.

METHODS

A case-control study was carried out in Cali-Colombia, comprised of 398 pregnant women (145 cases and 253 controls) who were believed to have periodontal disease, between 28 and 36 weeks of gestational age. Pre-eclampsia cases were defined as blood pressure > or = 140/90 mmHg and proteinuria > or = 0.3 g/24 h. Controls were pregnant women with normal blood pressure, without proteinuria, matched by maternal age, gestational age and body mass index. Sociodemographic data, obstetric risk factors, periodontal state, subgingival microbial composition and hs-CRP levels were determined in both groups.

RESULTS

The case and control groups were comparable for sociodemographic characteristics. In women with pre-eclampsia and confirmed periodontal disease (n = 138), hs-CRP levels increased according to the severity of the disease (gingivitis median 4.14 mg/dl; mild periodontitis median 4.70 mg/dl; moderate/severe periodontitis median 8.8 mg/dl; P = 0.01). A similar tendency was observed in controls with periodontal disease (n = 251), but it did not reach statistical significance (gingivitis median 5.10 mg/dl; mild periodontitis median 5.12 mg/dl; moderate/severe periodontitis median 6.90 mg/dl; P = 0.07). A significant difference in hs-CRP levels was observed in pre-eclamptic women with moderate/severe periodontitis compared to controls (P = 0.01).

CONCLUSION

These findings suggest that chronic periodontitis may increase hs-CRP levels in pregnant women and lead to complications such as pre-eclampsia.

Pathogenic implications for autoantibodies against C-reactive protein and other acute phase proteins

Systemic lupus erythematosus (SLE) is a systemic rheumatic disease characterized clinically by multiorgan involvement and serologically by the occurrence of antinuclear antibodies. SLE patients may present with multiple autoantibodies to cytoplasmic and cell surface antigens as well as to circulating plasma proteins. Another feature of SLE is that serum levels of C-reactive protein (CRP) often remain low despite high disease activity and despite high levels of other acute phase proteins and interleukin-6, i.e. the main CRP inducing cytokine. Apart from its important role as a laboratory marker of inflammation, CRP attracts increasing interest due to its many intriguing biological functions, one of which is a role as an opsonin contributing to the elimination of apoptotic cell debris, e.g. nucleosomes, thereby preventing immunization against autoantigens. Recently, autoantibodies against CRP and other acute phase proteins have been reported in certain rheumatic conditions, including SLE. Although the presence of anti-CRP autoantibodies does not explain the failed CRP response in SLE, antibodies directed against acute phase proteins have several implications of pathogenetic interest. This paper thus highlights the biological and clinical aspects of native and monomeric CRP and anti-CRP, as well as autoantibodies against mannose-binding lectin, serum amyloid A and serum amyloid P component.

Platelet aggregation and aspirin non-responsiveness increase when an acute coronary syndrome is complicated by an infection

BACKGROUND

Epidemiologic studies have shown that there is an association between acute respiratory infection and acute coronary syndrome. The aim of this study was to analyze the thrombotic risk, assessed by platelet aggregation and aspirin non-responsiveness, in patients with an acute coronary syndrome complicated by an infection.

METHODS

Patients with an acute coronary syndrome who were admitted to the intensive care unit and hospitalized for at least 3 days in 2002 and 2003 were eligible for the study. Three hundred and fifty-eight patients were included, of whom 66 had an infection during their hospital stay. Platelet aggregation was analyzed by an aggregometer using laser light (PA-200, laser light scattering). Aspirin non-responsiveness was defined as a closure time of

RESULTS

Platelet aggregation was more pronounced during an infectious complication (P < 0.001). The subgroups of patients with persistent fever, urinary tract infection, and pneumonia all had a higher level of aggregates than the group of patients without an infection (P = 0.007, P = 0.04, and P = 0.01, respectively). Aspirin non-responsiveness was more frequent in the group of subjects with pneumonia compared with those without an infection, 90% vs. 46% (P = 0.006). The CRP levels were independently associated with platelet aggregation and aspirin non-responsiveness (P < 0.001, P < 0.001, respectively).

CONCLUSION

An infectious complication during the course of an acute coronary syndrome leads to more pronounced platelet aggregation. Aspirin non-responsiveness is more frequent in severe infections, such as pneumonia. CRP is an independent predictor of platelet aggregation and aspirin non-responsiveness in the setting of an acute coronary syndrome.

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MESH Headings

• Acute Disease
• Aged
• Aged, 80 and over
• Aspirin/pharmacology
• Aspirin/therapeutic use
• Biomarkers/blood
• C-Reactive Protein/metabolism
• Drug Resistance
• Female
• Humans
• Linear Models
• Male
• Middle Aged
• Myocardial Ischemia/blood
• Myocardial Ischemia/complications
• Myocardial Ischemia/drug therapy
• Platelet Aggregation/drug effects
• Platelet Aggregation Inhibitors/pharmacology
• Platelet Aggregation Inhibitors/therapeutic use
• Platelet Function Tests
• Pneumonia/blood
• Pneumonia/complications
• Predictive Value of Tests
• Prognosis
• Risk Assessment
• Severity of Illness Index
• Syndrome
• Thrombosis/blood
• Thrombosis/etiology
• Thrombosis/prevention & control
• Treatment Failure
• Urinary Tract Infections/blood
• Urinary Tract Infections/complications

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Affiliation(s)

A Modica Department of Internal Medicine, Section of Cardiology, Ostersund Hospital, Ostersund, Sweden.
F Karlsson
T Mooe

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Collaborators Collapse

Cell membranes and liposomes dissociate C-reactive protein (CRP) to form a new, biologically active structural intermediate: mCRP(m)

Emerging evidence indicates that C-reactive protein (CRP) has at least two conformationally distinct isoforms, i.e., pentameric CRP (pCRP) and monomeric CRP (mCRP or CRP subunit). Both CRP isoforms are proposed to play roles in inflammation and may participate in the pathogenesis of cardiovascular disease. However, the origin of mCRP in situ and the interplay between the two CRP isoforms under physiological/pathological circumstances remain elusive. Herein, by probing conformational alteration, neoepitope expression, and direct visualization using electron-microscopy, we have shown that calcium-dependent binding of pCRP to membranes, including liposomes and cell membranes, led to a rapid but partial structural change, producing molecules that express CRP subunit antigenicity but with retained native pentameric conformation. This hybrid molecule is herein termed mCRP(m). The formation of mCRP(m) was associated with significantly enhanced complement fixation. mCRP(m) can further detach from membrane to form the well-recognized mCRP isoform converted in solution (mCRP(s)) and exert potent stimulatory effects on endothelial cells. The membrane-induced pCRP dissociation not only provides a physiologically relevant scenario for mCRP formation but may represent an important mechanism for regulating CRP function.

A nuclear receptor corepressor-dependent pathway mediates suppression of cytokine-induced C-reactive protein gene expression by liver X receptor

C-reactive protein (CRP), the prototypical human acute phase protein, is an independent risk predictor of future cardiovascular events, both in healthy individuals and in patients with known cardiovascular disease. In addition, previous studies indicate that CRP might have direct proatherogenic properties. Ligand activation of the liver X receptor (LXR), a member of the nuclear hormone receptor superfamily, inhibits inflammatory gene expression in macrophages and attenuates the development of atherosclerosis in various animal models. We demonstrate herein that 2 synthetic LXR ligands, T0901317 and GW3965, inhibit interleukin-1beta/interleukin-6-induced CRP mRNA and protein expression in human hepatocytes. Knockdown of LXRalpha/beta by short interfering RNAs completely abolished the inhibitory effect of the LXR agonist T0901317 on cytokine-induced CRP gene transcription. Transient transfection experiments with 5'-deletion CRP promoter constructs identified a region from -125 to -256 relative to the initiation site that mediated the inhibitory effect of LXR ligands on CRP gene transcription. Depletion of the nuclear receptor corepressor by specific short interfering RNA increased cytokine-inducible CRP mRNA expression and promoter activity and reversed LXR ligand-mediated repression of CRP gene transcription. Chromatin immunoprecipitation assays indicated that nuclear receptor corepressor is present on the endogenous CRP promoter under basal conditions. Cytokine-induced clearance of nuclear receptor corepressor complexes was inhibited by LXR ligand treatment, maintaining the CRP gene in a repressed state. Finally, treatment of C57Bl6/J mice with LXR ligands attenuated lipopolysaccharide-induced mouse CRP and serum amyloid P component gene expression in the liver, whereas no effect was observed in LXRalphabeta knockout mice. Our observations identify a novel mechanism of inflammatory gene regulation by LXR ligands. Thus, inhibition of CRP expression by LXR agonists may provide a promising approach to impact initiation and progression of atherosclerosis.

C-reactive protein in vulnerable coronary plaques

BACKGROUND

An increased level of serum C-reactive protein (CRP) is a known prognostic factor for acute coronary events and sudden cardiac death, and it is associated with coronary calcification. CRP is expressed in coronary arteries, but its role in the development of coronary plaques is unclear.

AIM

To investigate CRP immunoreactivity in relation to the severity of coronary artery disease and plaque morphology in human left anterior descending coronary arteries (LAD).

METHODS

A prospective, consecutive autopsy series of 66 patients (mean age 63.4 years) in Tampere University Hospital, Tampere, Finland.

RESULTS

CRP immunoreactivity was seen in 59% of the cases. In logistic regression analysis with age, sex and body mass index as confounders, CRP immunoreactivity in LAD was associated with >50% stenosis and plaque calcification. All three cases with acute coronary thrombosis due to rupture or erosion of the plaque showed a clear immunopositive reaction. CRP-positive cells were never detected in normal arteries, but were often found in early fibrous plaques (75%) and almost invariably present in the shoulder area of plaques with necrotic core (96%). CRP immunoreactivity adjacent to calcified areas in more stable plaques (71%) was less consistent with one-third of these plaques showing no immunoreactivity.

CONCLUSIONS

CRP immunoreactivity is associated with the progression of atherosclerosis, and especially with unstable coronary plaques. The immunoreactivity could cease at the stable calcified stages of atherosclerosis.