Vascular pentraxin 3 controls arterial thrombosis by targeting collagen and fibrinogen induced platelets aggregation.

AIM: The long pentraxin PTX3 plays a non-redundant role during acute myocardial infarction, atherosclerosis and in the orchestration of tissue repair and remodeling during vascular injury, clotting and fibrin deposition. The aim of this work is to investigate the molecular mechanisms underlying the protective role of PTX3 during arterial thrombosis. METHODS AND RESULTS: PTX3 KO mice transplanted with bone marrow from WT or PTX3 KO mice presented a significant reduction in carotid artery blood flow following FeCl3 induced arterial thrombosis (-80.36±11.5% and -95.53±4.46%), while in WT mice transplanted with bone marrow from either WT or PTX3 KO mice, the reduction was less dramatic (-45.55±1.37% and -53.39±9.8%), thus pointing to a protective effect independent of a hematopoietic cell's derived PTX3. By using P-selectin/PTX3 double KO mice, we further excluded a role for P-selectin, a target of PTX3 released by neutrophils, in vascular protection played by PTX3. In agreement with a minor role for hematopoietic cell-derived PTX3, platelet activation (assessed by flow cytometric expression of markers of platelet activation) was similar in PTX3 KO and WT mice as were haemostatic properties. Histological analysis indicated that PTX3 localizes within the thrombus and the vessel wall, and specific experiments with the N-terminal and the C-terminal PTX3 domain showed the ability of PTX3 to selectively dampen either fibrinogen or collagen induced platelet adhesion and aggregation. CONCLUSION: PTX3 interacts with fibrinogen and collagen and, by dampening their pro-thrombotic effects, plays a protective role during arterial thrombosis.

Pentraxin 3 (PTX3) plasma levels and carotid intima media thickness progression in the general population.

BACKGROUND AND AIM: Pentraxin 3 (PTX3) is an essential component of the humoral arm of innate immunity and, like C-reactive protein, is independently associated with the risk of developing vascular events. Aim of this study was to investigate, in two large population-based surveys, the Bruneck Study and the PLIC Study, whether PTX3 plasma levels predict the progression of common carotid artery intima-media thickness (CCA-IMT), a surrogate marker of atherosclerosis, in the general population during 5 or 6 years of follow-up. RESULTS: In the Bruneck Study, PTX3 plasma levels did not predict a faster progression of CCA-IMT either in the carotid artery or in the femoral artery. This finding was confirmed in the PLIC Study where subjects within the highest tertile of PTX3 did not show an increased progression of CCA-IMT. PTX3 plasma levels were also not associated with the fastest maximum IMT progression. In summary, in more than 2400 subjects from the general population, PTX3 plasma level is neither an independent predictor of progression of subclinical atherosclerosis in different arterial territories, including carotid and femoral arteries nor of incident cardiovascular events. CONCLUSION: These findings support the relevance of investigating the predictive value of PTX3 plasma levels only in specific settings, like overt CVD, heart failure or acute myocardial infarction.

Vaccination of mice for research purpose: alum is as effective as and safer than complete Freund adjuvant.

Systemic lupus erythematosus (SLE) is an autoimmune disease involving many organ systems. Glomerulonephritis (GLN) is one of the major causes of morbidity and mortality in SLE. It has recently been demonstrated that adjuvants of vaccines could cause the so called ASIA syndrome. The study aimed to assess the effects of Complete Freund's Adjuvant (CFA) vs alum injections in NZB/NZWF1 mice. Mice (n=10 each group) were injected with a total volume of 200 µL of: CFA in PBS (group 1), alum in PBS (group 2), PBS (group 3) as controls, PTX3/CFA (group 4), PTX3/alum (group 5), 3 times, 3 weeks apart /given in each injection, three weeks apart from ten weeks of age. Urine samples were collected weekly to evaluate proteinuria. Blood samples were collected before every injection, at 21 weeks of age, and at death to evaluate levels of anti-PTX3 and anti-dsDNA. Proteinuria free survival and survival rates were analyzed by the Kaplan-Meier method using Mantel-Cox's test for comparisons. CFA-treated mice developed both anti-dsDNA antibodies and proteinuria earlier and at higher levels than alumtreated and PBS-injected mice, starting from 13 weeks of age. Proteinuria free survival rates (proteinuria ≥ 300 mg/dL) and survival rates were lower in CFA-treated mice than those treated with alum or injected with PBS (P<0.001 for all). No difference was observed between the alum-treated group and PBS-injected mice. Notably, groups 4 and 5, immunized with PTX3, developed anti-PTX3 antibodies and no significant difference was observed. Alum seems to be as effective as and safer than CFA as adjuvant, since it did not affect disease progression in immunized NZB/NZWF1 mice.

The long pentraxin PTX3 at the crossroads between innate immunity and tissue remodelling.

Innate immunity represents the first line of defence against pathogens and plays key roles in the activation and orientation of the adaptive immune response. The innate immune system comprises both a cellular and a humoral arm. Components of the humoral arm include soluble pattern recognition molecules that recognize pathogen-associated molecular patterns and initiate the immune response in coordination with the cellular arm, therefore acting as functional ancestors of antibodies. Pentraxins are essential constituents of the humoral arm of innate immunity and represent a superfamily of highly conserved acute phase proteins, traditionally classified into short and long pentraxins. Pentraxin 3 (PTX3) is the prototypic member of the long pentraxins subfamily. As opposed to C-reactive protein, whose sequence and regulation have not been conserved during evolution from mouse to man, the evolutionary conservation of sequence, gene organization and regulation of PTX3 has allowed addressing its pathophysiological roles in genetically modified mice, in diverse conditions, ranging from infections to sterile inflammation, angiogenesis and female fertility. Despite this conservation, a number of predominantly non-coding polymorphisms have been identified in the PTX3 gene which, when associated in particular haplotypes, have been shown to be relevant in clinical conditions including infection and fertility. Here we review the studies on PTX3, with emphasis on pathogen recognition, tissue remodelling and crosstalk with other components of the innate immune system.

Endogenous PTX3 translocates at the membrane of late apoptotic human neutrophils and is involved in their engulfment by macrophages.

Neutrophils are short-lived innate immune cells that rapidly die by apoptosis. A rapid and efficient clearance of apoptotic cells is crucial to avoid autoimmunity. This process involves cell alterations, endocytic receptors expressed by phagocytic cells and soluble bridging molecules (opsonins) that facilitate internalization of apoptotic cells by phagocytes. Neutrophils constitutively express the prototypic long pentraxin PTX3 that binds to apoptotic cells and modulates their clearance. We thus evaluated whether endogenous PTX3 may interfere with the capture of apoptotic neutrophils. We observed that PTX3 accumulates in blebs at the surface of late apoptotic neutrophils, resulting from its active translocation from granules to the membrane. A neutralizing anti-PTX3 monoclonal Ab (mAb) inhibits the capture of late apoptotic neutrophils by macrophages. This study shows that intracellular PTX3 translocates at the surface of late apoptotic neutrophils and acts as an 'eat-me' molecule for their recognition and capture by macrophages.

Dynamic induction of the long pentraxin PTX3 in the CNS after limbic seizures: evidence for a protective role in seizure-induced neurodegeneration.

Pentraxin 3, a prototypic long pentraxin, is induced by proinflammatory signals in the brain. Inflammatory cytokines are rapidly induced in glia by epileptic activity. We show that pentraxin 3 immunoreactivity and mRNA are enhanced in the rat forebrain above undetectable control levels by limbic seizures with a dual pattern of induction. Within 6 h from seizure onset, pentraxin 3 immunoreactivity was increased in astrocytes. Eighteen to 48 h later, specific neuronal populations and leucocytes were strongly immunoreactive only in areas of neurodegeneration. This staining was abolished when neuronal cell loss, but not seizures, was prevented by blocking N-methyl-D-aspartate receptors. Pentraxin 3 -/- mice had a more widespread seizure-related neuronal damage in the forebrain than their wild-type littermates although both groups had similar epileptic activity. Our results provide evidence that pentraxin 3 is synthesized in brain after seizures and may exert a protective role in seizure-induced neurodegeneration.

Circulating levels of the long pentraxin PTX3 correlate with severity of infection in critically ill patients.

OBJECTIVE: To evaluate the recently discovered long pentraxin PTX3 in plasma of critically ill patients and to compare it with the classic short pentraxin C-reactive protein and with other indicators of inflammation. DESIGN: A cohort study on plasma samples. SETTING: Medical intensive care unit (ICU) of the University Hospital of Basel. PATIENTS: A total of 101 consecutive critically ill patients admitted to the medical ICU. INTERVENTIONS: Venous blood samples were routinely obtained at entry, on day 2, and at discharge or before death. MEASUREMENTS AND MAIN RESULTS: Plasma samples were obtained from 101 consecutive critically ill patients admitted to the ICU with systemic inflammatory response syndrome, sepsis, or septic shock. PTX3 plasma levels were measured by enzyme-linked immunosorbent assay. PTX3 was elevated in critically ill patients, with a gradient from systemic inflammatory response syndrome to septic shock. PTX3 levels correlated with clinical scores reflecting severity of disease (e.g., Acute Physiology and Chronic Health Evaluation II: p =.00097). In addition, high levels of PTX3 were associated with unfavorable outcome. CONCLUSIONS: The long pentraxin PTX3 is elevated in critically ill patients and correlates with severity of disease and infection. Compared with the short pentraxin C-reactive protein, PTX3 may be a more direct indicator of tissue involvement by inflammatory and infectious processes.

The long pentraxin PTX3 binds to apoptotic cells and regulates their clearance by antigen-presenting dendritic cells.

Pentraxins are acute-phase proteins produced in vivo during inflammatory reactions. Classical short pentraxins, C-reactive protein, and serum amyloid P component are generated in the liver in response to interleukin (IL)-6. The long pentraxin PTX3 is produced in tissues under the control of primary proinflammatory signals, such as lipopolysaccharide, IL-1 beta, and tumor necrosis factor-alpha, which also promote maturation of dendritic cells (DCs). Cell death commonly occurs during inflammatory reactions. In this study, it is shown that PTX3 specifically binds to dying cells. The binding was dose dependent and saturable. Recognition was restricted to extranuclear membrane domains and to a chronological window after UV irradiation or after CD95 cross-linking-induced or spontaneous cell death in vitro. PTX3 bound to necrotic cells to a lesser extent. Human DCs failed to internalize dying cells in the presence of PTX3, while they took up normally soluble or inert particulate substrates. These results suggest that PTX3 sequesters cell remnants from antigen-presenting cells, possibly contributing to preventing the onset of autoimmune reactions in inflamed tissues. (Blood. 2000;96:4300-4306)

Increased peripheral benzodiazepine binding sites and pentraxin 3 expression in the spinal cord during EAE: relation to inflammatory cytokines and modulation by dexamethasone and rolipram.

We have studied the mRNA expression of pentraxin 3 (PTX3) and the binding of the peripheral-type benzodiazepine receptor (PBR) ligand, [3H]-PK11195, in the spinal cord of Lewis rats where EAE was actively induced. PTX3 was induced during the active phase of EAE (day 10-14), it remained high up to 30 days and disappeared only 60 days later. Similarly, PK11195 binding peaked at day 14-17 during the recovery and it disappeared by day 60. On the other hand, the levels of TNF and IL-6 in the spinal cord were elevated at the peak and at the onset of clinical signs and returned to non-detectable by day 14-17. Dexamethasone abolished all these changes, while treatment with rolipram, delayed the appearance of the disease and then decreased its severity. However the peaks of TNF, IL-6, PBR and PTX3 levels in spinal cord were only delayed, but not reduced, by rolipram treatment. In conclusion, we show two types of inflammatory changes in EAE: acute, short term changes (TNF and IL-6), that correlate with the disease; and effects such as PTX3 expression and PK11195 binding that last longer after recovery from the disease.

Inducible expression of the long pentraxin PTX3 in the central nervous system.

PTX3 is a prototypic long pentraxin consisting of a C terminal 203-amino acid pentraxin-like domain coupled with an N-terminal 178-amino acid unrelated portion. PTX3 is induced by primary proinflammatory signals in various cell types, most prominently macrophages and endothelial cells. Other long pentraxins, such as murine or rat neuronal pentraxin 1 (NP1) and human neuronal pentraxin 2 (NPTX2), are expressed in the central nervous system (CNS). The present study was designed to investigate whether PTX3 is expressed in the brain and to define the structures and cells involved. Intracerebroventricular (i.c.v.), but not i.v., injection of LPS induced high levels of PTX3 mRNA in the mouse brain. In contrast NP1 is constitutively expressed in the murine CNS and is not modulated by LPS administration. I.c.v. IL-1beta was also a potent inducer of PTX3 expression in the CNS, whereas TNFalpha was substantially less effective and IL-6 induced a barely detectable signal. Central administration of LPS and IL-1 induced PTX3 also in the periphery (heart), whereas the reverse did not occur. Expression of PTX3 was also observed in the brain of mice infected with Candida albicans (C. albicans) or Cryptococcus neoformans. (C. neoformans). The kinetics of PTX3 gene induction were consistently different between C. albicans- and C. neoformans-infected mice, according to the diverse outcome of the CNS immune reaction. In situ hybridization revealed that i.c.v. injection of LPS induced a strong PTX3 expression in presumptive glial cells, in the white matter (corpus callosum, fimbria) and meningeal pia mater as well as in dentate gyrus hilus and granule cells. No constitutive expression of PTX3 was detected. Central expression of PTX3 may amplify mechanisms of innate resistance and damage in the CNS. The possibility of a direct interaction of PTX3 with neuronal cells, as suggested for NPTX2, remains to be explored.

Defective expression of the monocyte chemotactic protein-1 receptor CCR2 in macrophages associated with human ovarian carcinoma.

Monocyte chemotactic protein-1 (MCP-1, CCL2) is an important determinant of macrophage infiltration in tumors, ovarian carcinoma in particular. MCP-1 binds the chemokine receptor CCR2. Recent results indicate that proinflammatory and anti-inflammatory signals regulate chemokine receptor expression in monocytes. The present study was designed to investigate the expression of CCR2 in tumor-associated macrophages (TAM) from ovarian cancer patients. TAM isolated from ascitic or solid ovarian carcinoma displayed defective CCR2 mRNA (Northern blot and PCR) and surface expression and did not migrate in response to MCP-1. The defect was selective for CCR2 in that CCR1 and CCR5 were expressed normally in TAM. CCR2 gene expression and chemotactic response to MCP-1 were decreased to a lesser extent in blood monocytes from cancer patients. CCR2 mRNA levels and the chemotactic response to MCP-1 were drastically reduced in fresh monocytes cultured in the presence of tumor ascites from cancer patients. Ab against TNF-alpha restored the CCR2 mRNA level in monocytes cultured in the presence of ascitic fluid. The finding of defective CCR2 expression in TAM, largely dependent on local TNF production, is consistent with previous in vitro data on down-regulation of chemokine receptors by proinflammatory molecules. Receptor inhibition may serve as a mechanism to arrest and retain recruited macrophages and to prevent chemokine scavenging by mononuclear phagocytes at sites of inflammation and tumor growth. In the presence of advanced tumors or chronic inflammation, systemic down-regulation of receptor expression by proinflammatory molecules leaking in the systemic circulation may account for defective chemotaxis and a defective capacity to mount inflammatory responses associated with advanced neoplasia.

Autocrine production of IL-10 mediates defective IL-12 production and NF-kappa B activation in tumor-associated macrophages.

IL-12 is a central cytokine in the activation of inflammation and immunity and in the generation of Th1-type responses. Tumor-associated macrophages (TAM) from mouse and human tumors showed defective production of IL-12. Defective IL-12 production was associated with lack of p50/p65 NF-kappa B activation. TAM produced increased amounts of the immunosuppressive cytokine IL-10. Abs against IL-10 restored the defective capacity of TAM to produce IL-12. Our data suggest that during tumor growth an IL-10-dependent pathway of diversion of macrophage function can be activated into the tumor microenvironment and results in the promotion of the IL-10+ IL-12- phenotype of TAM. Blocking IL-10, as well as other immunosuppressive cytokines present in the tumor microenvironment, such as TGF-beta, may complement therapeutic strategies aimed at activating type I antitumor immune responses.

Multimer formation and ligand recognition by the long pentraxin PTX3. Similarities and differences with the short pentraxins C-reactive protein and serum amyloid P component.

PTX3 is a prototypic long pentraxin consisting of a C-terminal 203-amino acid pentraxin-like domain coupled with an N-terminal 178-amino acid unrelated portion. The present study was designed to characterize the structure and ligand binding properties of human PTX3, in comparison with the classical pentraxins C-reactive protein and serum amyloid P component. Sequencing of Chinese hamster ovary cell-expressed PTX3 revealed that the mature secreted protein starts at residue 18 (Glu). Lectin binding and treatment with N-glycosidase F showed that PTX3 is N-glycosylated, sugars accounting for 5 kDa of the monomer mass (45 kDa). Circular dichroism analysis indicated that the protein consists predominantly of beta-sheets with a minor alpha-helical component. While in gel filtration the protein is eluted with a molecular mass of congruent with900 kDa, gel electrophoresis using nondenaturing, nonreducing conditions revealed that PTX3 forms multimers predominantly of 440 kDa apparent molecular mass, corresponding to decamers, and that disulfide bonds are required for multimer formation. The ligand binding properties of PTX3 were then examined. As predicted based on modeling, inductive coupled plasma/atomic emission spectroscopy showed that PTX3 does not have coordinated Ca2+. Unlike the classical pentraxins CRP and SAP, PTX3 did not bind phosphoethanolamine, phosphocholine, or high pyruvate agarose. PTX3 in solution, bound to immobilized C1q, but not C1s, and, reciprocally, C1q bound to immobilized PTX3. Binding of PTX3 to C1q is specific and saturable with a Kd 7.4 x 10(-8) M as determined by solid phase binding assay. The Chinese hamster ovary cell-expressed pentraxin domain bound C1q when multimerized. Thus, as predicted on the basis of computer modeling, the prototypic long pentraxin PTX3 forms multimers, which differ from those formed by classical pentraxins in terms of protomer composition and requirement for disulfide bonds, and does not recognize CRP/SAP ligands. The capacity to bind C1q, mediated by the pentraxin domain, is consistent with the view that PTX3, produced in tissues by endothelial cells or macrophages in response to interleukin-1 and tumor necrosis factor, may act as a local regulator of innate immunity.

Identification of MIP-1 alpha/LD78 as a monocyte chemoattractant released by the HTLV-I-transformed cell line MT4.

It is known that the HTLV-I-transformed cell line MT4 releases chemotactic activity for monocytes spontaneously. The MT4 monocyte chemoattractant was purified to homogeneity and sequencing of 25 amino acids revealed identity with the C-C chemokine macrophage inflammatory protein-1 alpha (MIP-1 alpha/LD78). An anti-MIP-1 alpha/LD78 rabbit antiserum substantially inhibited chemotaxis of the MT4 chemoattractant. MT4 cells constitutively expressed MIP-1 alpha/LD78 but not the C-C chemokines MCP-1, RANTES, and MIP-1 beta/Act2 and the C-X-C chemokines IL-8, gro alpha, and gro beta. MT4-derived MIP-1 alpha/LD78 was active on monocytes but was a weak chemoattractant for polymorphonuclear leukocytes. Thus, MIP-1 alpha/LD78 is a major monocyte chemoattractant released by HTLV-I-transformed T cells. Expression of MIP-1 alpha/LD78, a leukocyte chemotactic and myelosuppressive molecule, may play an important role in the manifestations of HTLV-I-related diseases.

Cytokine regulation of monocyte recruitment.

Phagocytes infiltrating neoplastic tissues have peculiar membrane phenotype and functional properties. Tumor-associated macrophages (TAM) play a complex, ambiguous role in the regulation of primary tumor growth and metastasis (a "macrophage balance"). Yet these cells are strategically located at the very interface between tumor and host and represent a potential target for immunomodulation. A better understanding of the regulation and function of TAM may provide a less empirical basis of or rational design of therapeutic approaches, as vividly illustrated by the antitumor activity of i.p. in IFN ovarian cancer patients with minimal residual disease resistant to chemotherapy.

Inducible expression of PTX3, a new member of the pentraxin family, in human mononuclear phagocytes.

The pentraxins C-reactive protein (CRP) and serum amyloid P component (SAP) are acute-phase proteins produced by liver epithelial cells. PTX3 was recently cloned as an interleukin-1 (IL-1)-inducible gene in endothelial cells, with structural similarities to pentraxins in the C-terminal half of the molecule. The present study was designed to investigate the expression of PTX3 in the human leukocyte populations. Human peripheral blood mononuclear cells exposed to lipopolysaccharide (LPS) or IL-1 beta expressed significant levels of PTX3 mRNA. Tumor necrosis factor-alpha (TNF-alpha) was a less-effective inducer of PTX3, whereas IL-6, monocyte chemotactic protein-1, macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and interferon-gamma were inactive. Among leukocytes, only monocytes exposed to inflammatory cytokines or LPS expressed the PTX3 transcript, which was undetectable in resting or stimulated polymorphonuclear cells, T or B lymphocytes, and natural killer cells. PTX3 mRNA was also inducible in in vitro monocyte-derived macrophages, in tumor-associated macrophages, and in the myelomonocytic cell lines HL60, U937, and THP1, but not in GFD8, with the latter possibly representative of earlier stages of myelomonocytic differentiation. T- and B-cell lines had no detectable PTX3. Inhibition of transcription by actinomycin D blocked induction of PTX3 in monocytes and nuclear run-on analysis showed that LPS induces the expression of the PTX3 gene at the transcriptional level in isolated monocytes. Cycloheximide had no effect on PTX3 induction in U937 cells, but was inhibitory on monocytes exposed to LPS or IL-1 beta. Monoclonal antibody against TNF and the IL-1 receptor antagonists did not inhibit induction of PTX3 in monocytes by LPS, thus excluding these cytokines as secondary stimulators of PTX3. IL-4, but not dexamethasone or transforming growth factor-beta, inhibited PTX3 expression in monocytes. Using a PTX3-specific antiserum, release of PTX3 protein was demonstrated for the first time in stimulated monocytes as well as in endothelial and fibroblastic cells. Thus, PTX3, unlike the classical pentraxins CRP and SAP, is expressed and released by cells of the monocyte-macrophage lineage exposed to inflammatory signals.

Interleukin-1-inducible genes in endothelial cells. Cloning of a new gene related to C-reactive protein and serum amyloid P component.

Differential screening of a cDNA library constructed from human umbilical vein endothelial cells exposed for 1 h to interleukin-1 beta (IL-1 beta) has led to the identification of a novel gene (PTX3) related to pentaxins (C-reactive protein and serum amyloid P component in man), a subclass of acute phase proteins. Sequencing of the full-length cDNA clone and RNase mapping revealed that the PTX3 transcript is 1861 base pairs long and has a unique transcription start site. The predicted protein sequence of 381 amino acids is highly similar to pentaxins in its COOH-terminal half where it also contains a typical 8-amino acid "pentaxin signature" sequence. The NH2-terminal half of PTX3 shows no similarity to any known protein sequence and initiates with a putative signal peptide indicating that PTX3 is secreted. The genome of PTX3 is organized into three exons. Interestingly, the region of homology between PTX3 and pentaxins corresponds to the third PTX3 exon. The PTX3 gene has been localized on human chromosome 3 band q25 by Southern blots of somatic cell hybrids and by in situ hybridization. The PTX3 mRNA is induced in endothelial, hepatic, and fibroblastic cells by IL-1 beta and tumor necrosis factor alpha but not by IL-6 and interferon-gamma. PTX3 may represent a novel marker of inflammatory reactions, particularly those involving the vessel wall.