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

Regulation of Conformational Changes in C-reactive Protein Alters its Bioactivity

The acute phase C-reactive protein (CRP) is mainly synthesized and secreted by the liver in a cytokine-mediated response to infection or inflammation and circulates as a pentamer (pCRP) in plasma. Recent studies indicate that CRP is not only a marker but is directly involved in inflammation. CRP has a vital role in host defense and inflammation, metabolic function and scavenging through its ability for calcium depended binding to exogenous and endogenous molecules having phosphocholine followed by activation of the classical complement pathway. Accumulating evidence indicates that pCRP dissociates into monomeric CRP (mCRP) and most proinflammatory actions of CRP are only expressed following dissociation of its native pentameric assembly into mCRP. The dissociation of CRP into mCRP altogether promotes the ligand-binding capability. mCRP emerges to be the main conformation of CRP that participates in the regulation of local inflammation, however, little is identified concerning what triggers the significantly enhanced actions of mCRP and their binding to diverse ligands. The separation of mCRP from pCRP may be a direct relationship between CRP and inflammation. Here we review the current literature on CRP dissociation and its interaction with different ligands. The possibility to avoid the generation of the proinflammatory potential of mCRP has driven therapeutic approaches by targeting the dissociation mechanism of pCRP or inhibition of mCRP itself during inflammation.

Hematopoiesis, Inflammation and Aging-The Biological Background and Clinical Impact of Anemia and Increased C-Reactive Protein Levels on Elderly Individuals

Anemia and systemic signs of inflammation are common in elderly individuals and are associated with decreased survival. The common biological context for these two states is then the hallmarks of aging, i.e., genomic instability, telomere shortening, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion and altered intercellular communication. Such aging-associated alterations of hematopoietic stem cells are probably caused by complex mechanisms and depend on both the aging of hematopoietic (stem) cells and on the supporting stromal cells. The function of inflammatory or immunocompetent cells is also altered by aging. The intracellular signaling initiated by soluble proinflammatory mediators (e.g., IL1, IL6 and TNFα) is altered during aging and contributes to the development of both the inhibition of erythropoiesis with anemia as well as to the development of the acute-phase reaction as a systemic sign of inflammation with increased CRP levels. Both anemia and increased CRP levels are associated with decreased overall survival and increased cardiovascular mortality. The handling of elderly patients with inflammation and/or anemia should in our opinion be individualized; all of them should have a limited evaluation with regard to the cause of the abnormalities, but the extent of additional and especially invasive diagnostic evaluation should be based on an overall clinical evaluation and the possible therapeutic consequences.

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.

Copper-To-Zinc Ratio as an Inflammatory Marker in Patients with Sickle Cell Disease

Sickle cell disease (SCD) is an inherited disorder and a major health challenge in Nigeria. Micronutrient deficiencies often associated with the disorder may cause inflammation and abnormal metabolism in the body. The copper-to-zinc ratio is a more relevant diagnostic measure than the concentration of either metal alone in clinical practice. This study seeks to evaluate serum levels of c-reactive protein (CRP), copper, zinc and the copper-to-zinc ratio, and to correlate the latter with CRP in adult subjects with SCD. Serum copper, zinc, CRP and plasma fibrinogen were assayed in 100 confirmed SCD patients in steady clinical state and 100 age- and sex-matched subjects with normal hemoglobin. Serum copper and zinc were assayed by the colorimetric method using reagents supplied by Centronic, Germany, while CRP and fibrinogen were assayed using reagents supplied by Sigma (St. Louis, MO, USA) and Anogen (Ontario, Canada), respectively. The copper-to-zinc ratio was calculated from serum levels of copper and zinc. The measured parameters were compared between the groups using the Students t-test, and the Pearson correlation coefficient was used to relate CRP with the other parameters. Serum copper, CRP, fibrinogen and the copper-to-zinc ratio were significantly higher (p < 0.001), while zinc level was lower in SCD patients than in controls. Serum CRP concentration correlated with copper (r = 0.10; p < 0.02), zinc (r = −0.199; p < 0.05) and the copper-to-zinc ratio (r = 0.312; p < 0.002), but the correlation between CRP and fibrinogen was not significant. Inflammation may modulate copper and zinc homeostasis, and the copper-to-zinc ratio may be used as a marker of nutritional deficiency and inflammation in SCD patients.

C-Reactive Protein and Cancer-Diagnostic and Therapeutic Insights

Cancer disease describes any pathology involving uncontrolled cell growth. As cells duplicate, they can remain localized in defined tissues, forming tumor masses and altering their microenvironmental niche, or they can disseminate throughout the body in a metastatic process affecting multiple tissues and organs. As tumors grow and metastasize, they affect normal tissue integrity and homeostasis which signals the body to trigger the acute phase inflammatory response. C-reactive protein (CRP) is a predominant protein of the acute phase response; its blood levels have long been used as a minimally invasive index of any ongoing inflammatory response, including that occurring in cancer. Its diagnostic significance in assessing disease progression or remission, however, remains undefined. By considering the recent understanding that CRP exists in multiple isoforms with distinct biological activities, a unified model is advanced that describes the relevance of CRP as a mediator of host defense responses in cancer. CRP in its monomeric, modified isoform (mCRP) modulates inflammatory responses by inserting into activated cell membranes and stimulating platelet and leukocyte responses associated with acute phase responses to tumor growth. It also binds components of the extracellular matrix in involved tissues. Conversely, CRP in its pentameric isoform (pCRP), which is the form quantified in diagnostic measurements of CRP, is notably less bioactive with weak anti-inflammatory bioactivity. Its accumulation in blood is associated with a continuous, low-level inflammatory response and is indicative of unresolved and advancing disease, as occurs in cancer. Herein, a novel interpretation of the diagnostic utility of CRP is presented accounting for the unique properties of the CRP isoforms in the context of the developing pro-metastatic tumor microenvironment.

How C-Reactive Protein Structural Isoforms With Distinctive Bioactivities Affect Disease Progression

C-reactive protein (CRP) is a widely known, hepatically synthesized protein whose blood levels change rapidly and pronouncedly in response to any tissue damaging event associated with an inflammatory response. The synthesis and secretion of CRP is stimulated by interleukin-6, an early pleiotropic cytokine released by macrophages, endothelial, and other cells that are activated when localized normal tissue structures are compromised by trauma or disease. Serum CRP levels can change rapidly and robustly from 10-100-fold within 6–72 h of any tissue damaging event. Elevated blood levels correlate with the onset and extent of both activated inflammation and the acute phase biochemical response to the tissue insult. Because its functional bioactivity as the prototypic acute phase reactant has eluded clear definition for decades, diagnosticians of various conditions and diseases use CRP blood levels as a simple index for ongoing inflammation. In many pathologies, which involves many different tissues, stages of disease, treatments, and responses to treatments, its interpretive diagnostic value requires a deeper understanding of the localized tissue processes and events that contribute signals which regulate protective or pathological host defense bioactivities. This report presents concepts that describe how local tissue activation events can lead to a non-proteolytic, conformational rearrangement of CRP into a unique isoform with distinctive solubility, antigenicity, binding reactivities and bioactivities from that protein widely known and measured in serum. By describing factors that control the expression, tissue localization, half-life and pro-inflammatory amplification activity of this CRP isoform, a unifying explanation for the diagnostic significance of CRP measurement in disease is advanced.

Combined C-Reactive Protein and Novel Inflammatory Parameters as a Predictor in Cancer-What Can We Learn from the Hematological Experience?

The acute phase reaction is a systemic response to acute or chronic inflammation. The serum level of C-reactive protein (CRP) is the only acute phase biomarker widely used in routine clinical practice, including its uses for prognostics and therapy monitoring in cancer patients. Although Interleukin 6 (IL6) is a main trigger of the acute phase reactions, a series of acute phase reactants can contribute (e.g., other members in IL6 family or IL1 subfamily, and tumor necrosis factor α). However, the experience from patients receiving intensive chemotherapy for hematological malignancies has shown that, besides CRP, other biomarkers (e.g., cytokines, soluble cytokine receptors, soluble adhesion molecules) also have altered systemic levels as a part of the acute phase reaction in these immunocompromised patients. Furthermore, CRP and white blood cell counts can serve as a dual prognostic predictor in solid tumors and hematological malignancies. Recent studies also suggest that biomarker profiles as well as alternative inflammatory mediators should be further developed to optimize the predictive utility in cancer patients. Finally, the experience from allogeneic stem cell transplantation suggests that selected acute phase reactants together with specific markers of organ damages are useful for predicting or diagnosing graft versus host disease. Acute phase proteins may also be useful to identify patients (at risk of) developing severe immune-mediated toxicity after anticancer immunotherapy. To conclude, future studies of acute phase predictors in human malignancies should not only investigate the conventional inflammatory mediators (e.g., CRP, white blood cell counts) but also combinations of novel inflammatory parameters with specific markers of organ damages.

Copper-to-Zinc Ratio Correlates with an Inflammatory Marker in Patients with Sickle Cell Disease

Sickle cell disease (SCD) is an inherited disorder of major health challenge in Nigeria. Micronutrients deficiencies often associated with the disorder may cause inflammation and abnormal metabolisms in the body. The copper-to-zinc ratio is a more important assessment than the concentrations of either of the metals in clinical practice. This study seeks to evaluate serum levels of c-reactive protein (CRP), copper, zinc and copper-to-zinc ratio and to correlate copper-to-zinc ratio with CRP in adult subjects with SCD. Serum copper, zinc, CRP and plasma fibrinogen were assayed in 100 confirmed SCD patients in steady clinical state and 100 age and sex matched subjects with normal haemoglobin. Serum copper and zinc were assayed by colorimetric method using reagents supplied by Centronic, Germany while CRP and fibrinogen were assayed using reagents supplied by Sigma (St. Louis, MO, USA) and Anogen (Ontario, Canada), respectively. The copper to zinc ratio was calculated from serum levels of copper and zinc. The measured parameters were compared between the groups using Students t-test and Pearson correlation coefficient was used to relate CRP with the other parameters. Serum copper, CRP, fibrinogen and copper-to-zinc ratio were significantly higher (p < 0.001) while zinc level was lower in SCD patients than controls. Serum CRP concentration correlated with copper (r = 0.10; p < 0.02), zinc (r = −0.199; p < 0.05) and Copper-to-zinc ratio (r = 0.312; p < 0.002) but the correlation between CRP and fibrinogen was not significant. Inflammatory condition may modulate copper and zinc homeostasis and copper-to-zinc ratio may be used as marker of nutritional deficiency and inflammation in SCD patients.

Regulation of C-reactive protein conformation in inflammation

C-reactive protein (CRP) is a non-specific diagnostic marker of inflammation and an evolutionarily conserved protein with roles in innate immune signaling. Natural CRP is composed of five identical globular subunits that form a pentamer, but the role of pentameric CRP (pCRP) during inflammatory pathogenesis remains controversial. Emerging evidence suggests that pCRP can be dissociated into monomeric CRP (mCRP) that has major roles in host defenses and inflammation. Here, we discuss our current knowledge of the dissociation mechanisms of pCRP and summarize the stepwise conformational transition model to mCRP to elucidate how CRP dissociation contributes to proinflammatory activity. These discussions will evoke new understanding of this ancient protein.

Copper-to-Zinc Ratio Correlates with an Inflammatory Marker in Patients with Sickle Cell Disease (Version 1)

Sickle cell disease (SCD) is an inherited disorder of major health challenge in Nigeria. Micronutrients deficiencies often associated with the disorder may cause inflammation and abnormal metabolisms in the body. The copper-to-zinc ratio is a more important assessment than the concentrations of either of the metals in clinical practice. This study seeks to evaluate serum levels of c-reactive protein (CRP), copper, zinc and copper-to-zinc ratio and to correlate copper-to-zinc ratio with CRP in adult subjects with SCD. Serum copper, zinc, CRP and plasma fibrinogen were assayed in 100 confirmed SCD patients in steady clinical state and 100 age and sex matched subjects with normal haemoglobin. Serum copper and zinc were assayed by colorimetric method using reagents supplied by Centronic, Germany while CRP and fibrinogen were assayed using reagents supplied by Sigma (St. Louis, MO, USA) and Anogen (Ontario, Canada), respectively. The copper to zinc ratio was calculated from serum levels of copper and zinc. The measured parameters were compared between the groups using Students t-test and Pearson correlation coefficient was used to relate CRP with the other parameters. Serum copper, CRP, fibrinogen and copper-to-zinc ratio were significantly higher (p < 0.001) while zinc level was lower in SCD patients than controls. Serum CRP concentration correlated with copper (r = 0.10; p < 0.02), zinc (r = −0.199; p < 0.05) and Copper-to-zinc ratio (r = 0.312; p < 0.002) but the correlation between CRP and fibrinogen was not significant. Inflammatory condition may modulate copper and zinc homeostasis and copper-to-zinc ratio may be used as marker of nutritional deficiency and inflammation in SCD patients.

Neutralization of viral infectivity by zebrafish c-reactive protein isoforms

This work explores the unexpected in vivo and in vitro anti-viral functions of the seven c-reactive protein (crp1-7) genes of zebrafish (Danio rerio). First results showed heterogeneous crp1-7 transcript levels in healthy wild-type zebrafish tissues and organs and how those levels heterogeneously changed not only after bacterial but also after viral infections, including those in adaptive immunity-deficient rag1^-/- mutants. As shown by microarray hybridization and proteomic techniques, crp2/CRP2 and crp5/CRP5 transcripts/proteins were among the most modulated during in vivo viral infection situations including the highest responses in the absence of adaptive immunity. In contrast crp1/CRP1/and crp7/CRP7 very often remained unmodulated. All evidences suggested that zebrafish crp2-6/CRP2-6 may have in vivo anti-viral activities in addition to their well known anti-bacterial and/or physiological functions in mammalians. Confirming those expectations, in vitro neutralization and in vivo protection against spring viremia carp virus (SVCV) infections were demonstrated by crp2-6/CRP2-6 using crp1-7 transfected and/or CRP1-7-enriched supernatant-treated fish cells and crp2-5-injected one-cell stage embryo eggs, respectively. All these findings discovered a crp1-7/CRP1-7 primitive anti-viral functional diversity.These findings may help to study similar functions on the one-gene-coded human CRP, which is widely used as a clinical biomarker for bacterial infections, tissue inflammation and coronary heart diseases.

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.

An Intrinsically Disordered Motif Mediates Diverse Actions of Monomeric C-reactive Protein

Most proinflammatory actions of C-reactive protein (CRP) are only expressed following dissociation of its native pentameric assembly into monomeric form (mCRP). However, little is known about what underlies the greatly enhanced activities of mCRP. Here we show that a single sequence motif, i.e. cholesterol binding sequence (CBS; a.a. 35-47), is responsible for mediating the interactions of mCRP with diverse ligands. The binding of mCRP to lipoprotein component ApoB, to complement component C1q, to extracellular matrix components fibronectin and collagen, to blood coagulation component fibrinogen, and to membrane lipid component cholesterol, are all found to be markedly inhibited by the synthetic CBS peptide but not by other CRP sequences tested. Likewise, mutating CBS in mCRP also greatly impairs these interactions. Functional experiments further reveal that CBS peptide significantly reduces the effects of mCRP on activation of endothelial cells in vitro and on acute induction of IL-6 in mice. The potency and specificity of CBS are critically determined by the N-terminal residues Cys-36, Leu-37, and His-38; while the versatility of CBS appears to originate from its intrinsically disordered conformation polymorphism. Together, these data unexpectedly identify CBS as the major recognition site of mCRP and suggest that this motif may be exploited to tune the proinflammatory actions of mCRP.

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.

C-reactive Protein and Disease Outcome in Nigerian Sickle Cell Disease Patients

Background:

Evidence suggests that sickle cell disease (SCD) is associated with a chronic inflammatory state. C-reactive protein (CRP) is known to modulate inflammation. Its role in the chronic inflammation of SCD may make it valuable as a therapeutic target.

Aim:

The aim was to determine CRP levels in SCD subjects in asymptomatic steady state (ASS) and crisis and correlate these with severity scores in the ASS.

Subjects and Methods:

We measured the level of CRP in 30 hemoglobin SS (HbSS) individuals in ASS and seven in crisis. As controls, we measured CRP in 50 individuals each who were hemoglobin AS and hemoglobin AA respectively, using enzyme linked immunoabsorbent assay based commercially available kits from East Wing Diagnostic Limited Full blood count (white blood cell [WBC]) was done for the ASS HbSS individuals using a cell counter and their disease severity calculated by an objective scoring method.

Results:

Our results showed that ASS HbSS individuals had significantly higher CRP levels compared with the controls. The HbSS individuals in crisis also had a significantly higher level of CRP compared to the ASS HbSS individuals. Disease severity and WBC were found to be negatively correlated with CRP levels (P = 0.17; and 0.73, respectively).

Conclusion:

Our results suggest that increased levels of CRP in ASS HbSS individuals may play a protective role in SCD leading to better disease outcome, and may have value as a therapeutic target.

Serum amyloid P inhibits granulocyte adhesion

Background

The extravasation of granulocytes (such as neutrophils) at a site of inflammation is a key aspect of the innate immune system. Signals from the site of inflammation upregulate granulocyte adhesion to the endothelium to initiate extravasation, and also enhance granulocyte adhesion to extracellular matrix proteins to facilitate granulocyte movement through the inflamed tissue. During the resolution of inflammation, other signals inhibit granulocyte adhesion to slow and ultimately stop granulocyte influx into the tissue. In a variety of inflammatory diseases such as acute respiratory distress syndrome, an excess infiltration of granulocytes into a tissue causes undesired collateral damage, and being able to reduce granulocyte adhesion and influx could reduce this damage.

Results

We found that serum amyloid P (SAP), a constitutive protein component of the blood, inhibits granulocyte spreading and granulocyte adhesion to extracellular matrix components. This indicates that in addition to granulocyte adhesion inhibitors that are secreted during the resolution of inflammation, a granulocyte adhesion inhibitor is present at all times in the blood. Although SAP affects adhesion, it does not affect the granulocyte adhesion molecules CD11b, CD62L, CD18, or CD44. SAP also has no effect on the production of hydrogen peroxide by resting or stimulated granulocytes, or N-formyl-methionine-leucine-phenylalanine (fMLP)-induced granulocyte migration. In mice treated with intratracheal bleomycin to induce granulocyte accumulation in the lungs, SAP injections reduced the number of granulocytes in the lungs.

Conclusions

We found that SAP, a constitutive component of blood, is a granulocyte adhesion inhibitor. We hypothesize that SAP allows granulocytes to sense whether they are in the blood or in a tissue.

Bidirectional crosstalk between platelets and monocytes initiated by Toll-like receptor: an important step in the early defense against fungal infections?

Monocytes are important in the defense against fungal infections due to their phagocytic and immunoregulatory functions. Platelets also contribute in such immune responses through their release of soluble mediators, including chemokines as well as several other soluble mediators. Both monocytes and platelets express several Toll-like receptors (TLRs) that can recognize fungal molecules and thus initiate intracellular signaling events. TLR ligation on monocytes and platelets may thereby be an early immunological event and function as an initiator of a local proinflammatory crosstalk between platelets and monocytes resulting in (i) monocyte-induced increase of platelet activation and (ii) platelet-associated enhancement of the monocyte activation/function. These effects may have clinical implications both for the efficiency of antifungal treatment and for the predisposition to fungal infections, for example, increased predisposition in patients with thrombocytopenia/monocytopenia due to chemotherapy- or disease-induced bone marrow failure.