Giuseppe Peri

Non-redundant role of the long pentraxin PTX3 in anti-fungal innate immune response

Pentraxins are a superfamily of conserved proteins that are characterized by a cyclic multimeric structure. The classical short pentraxins, C-reactive protein (CRP) and serum amyloid P component (SAP), are acute-phase proteins produced in the liver in response to inflammatory mediators. Short pentraxins regulate innate resistance to microbes and the scavenging of cellular debris and extracellular matrix components. In contrast, long pentraxins have an unrelated, long amino-terminal domain coupled to the carboxy-terminal pentraxin domain, and differ, with respect to short pentraxins, in their gene organization, chromosomal localization, cellular source, and in their stimuli-inducing and ligand-recognition ability. To investigate the in vivo function of the long pentraxin PTX3, we generated mice deficient in Ptx3 by homologous recombination. Ptx3-null mice were susceptible to invasive pulmonary aspergillosis. Ptx3 binds selected microbial agents, including conidia of Aspergillus fumigatus, and we found that susceptibility of Ptx3-null mice was associated with defective recognition of conidia by alveolar macrophages and dendritic cells, as well as inappropriate induction of an adaptive type 2 response. Thus, the long pentraxin Ptx3 is a secreted pattern-recognition receptor that has a non-redundant role in resistance to selected microbial agents, in particular to the opportunistic fungal pathogen Aspergillus fumigatus.

The humoral pattern recognition receptor PTX3 is stored in neutrophil granules and localizes in extracellular traps

The long pentraxin (PTX) 3 is produced by macrophages and myeloid dendritic cells in response to Toll-like receptor agonists and represents a nonredundant component of humoral innate immunity against selected pathogens. We report that, unexpectedly, PTX3 is stored in specific granules and undergoes release in response to microbial recognition and inflammatory signals. Released PTX3 can partially localize in neutrophil extracellular traps formed by extruded DNA. Eosinophils and basophils do not contain preformed PTX3. PTX3-deficient neutrophils have defective microbial recognition and phagocytosis, and PTX3 is nonredundant for neutrophil-mediated resistance against Aspergillus fumigatus. Thus, neutrophils serve as a reservoir, ready for rapid release, of the long PTX3, a key component of humoral innate immunity with opsonic activity.

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 withN-glycosidase F showed that PTX3 isN-glycosylated, sugars accounting for 5 kDa of the monomer mass (45 kDa). Circular dichroism analysis indicated that the protein consists predominantly of β-sheets with a minor α-helical component. While in gel filtration the protein is eluted with a molecular mass of ≅900 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 K d 7.4 × 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.

PTX3, A Prototypical Long Pentraxin, Is an Early Indicator of Acute Myocardial Infarction in Humans

BACKGROUND Inflammation is an important component of ischemic heart disease. PTX3 is a long pentraxin whose expression is induced by cytokines in endothelial cells, mononuclear phagocytes, and myocardium. The possibility that PTX3 is altered in patients with acute myocardial infarction (AMI) has not yet been tested. METHODS AND RESULTS Blood samples were collected from 37 patients admitted to the coronary care unit (CCU) with symptoms of AMI. PTX3 plasma concentrations, as measured by ELISA, higher than the mean+2 SD of age-matched controls (2.01 ng/mL) were found in 27 patients within the first 24 hours of CCU admission. PTX3 peaked at 7.5 hours after CCU admission, and mean peak concentration was 6.94+/-11.26 ng/mL. Plasma concentrations of PTX3 returned to normal in all but 3 patients at hospital discharge and were unrelated to AMI site or extent, Killip class at entry, hours from symptom onset, and thrombolysis. C-reactive protein peaked in plasma at 24 hours after CCU admission, much later than PTX3 (P<0.001). Patients >64 years old and women had significantly higher PTX3 concentrations at 24 hours (P<0.05). PTX3 was detected by immunohistochemistry in normal but not in necrotic myocytes. CONCLUSIONS PTX3 is present in the intact myocardium, increases in the blood of patients with AMI, and disappears from damaged myocytes. We suggest that PTX3 is an early indicator of myocyte irreversible injury in ischemic cardiomyopathy.

Prognostic Significance of the Long Pentraxin PTX3 in Acute Myocardial Infarction

Background—Inflammation has a pathogenetic role in acute myocardial infarction (MI). Pentraxin-3 (PTX3), a long pentraxin produced in response to inflammatory stimuli and highly expressed in the heart, was shown to peak in plasma ≈7 hours after MI. The aim of this study was to assess the prognostic value of PTX3 in MI compared with the best-known and clinically relevant biological markers. Methods and Results—In 724 patients with MI and ST elevation, PTX3, C-reactive protein (CRP), creatine kinase (CK), troponin T (TnT), and N-terminal pro-brain natriuretic peptide (NT-proBNP) were assayed at entry, a median of 3 hours, and the following morning, a median of 22 hours from symptom onset. With respect to outcome events occurring over 3 months after the index event, median PTX3 values were 7.08 ng/mL in event-free patients, 16.12 ng/mL in patients who died, 9.12 ng/mL in patients with nonfatal heart failure, and 6.88 ng/mL in patients with nonfatal residual ischemia (overall P<0.0001). Multivariate analysis including CRP, CK, TnT, and NT-proBNP showed that only age ≥70 years (OR, 2.11; 95% CI, 1.04 to 4.31), Killip class >1 at entry (OR, 2.20; 95% CI, 1.14 to 4.25), and PTX3 (>10.73 ng/mL) (OR, 3.55; 95% CI, 1.43 to 8.83) independently predicted 3-month mortality. Biomarkers predicting the combined end point of death and heart failure in survivors were the highest tertile of PTX3 and of NT-proBNP and a CK ratio >6. Conclusions—In a representative contemporary sample of patients with MI with ST elevation, the acute-phase protein PTX3 but not the liver-derived short pentraxin CRP or other cardiac biomarkers (NT-proBNP, TnT, CK) predicted 3-month mortality after adjustment for major risk factors and other acute-phase prognostic markers.

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

ObjectiveTo 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. DesignA cohort study on plasma samples. SettingMedical intensive care unit (ICU) of the University Hospital of Basel. PatientsA total of 101 consecutive critically ill patients admitted to the medical ICU. InterventionsVenous 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. ConclusionsThe 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.

PTX3 in small‐vessel vasculitides: An independent indicator of disease activity produced at sites of inflammation

OBJECTIVE To verify whether the prototypical long pentraxin PTX3 represents an indicator of the activity of small-vessel vasculitis. METHODS Concentrations of PTX3, a pentraxin induced in endothelium by cytokines, were measured by enzyme-linked immunosorbent assay in the sera of 43 patients with Churg-Strauss syndrome, Wegeners granulomatosis, and microscopic polyangiitis. PTX3 was also measured in the sera of 28 patients with systemic lupus erythematosus (SLE), 22 with rheumatoid arthritis, and 16 with CREST syndrome (calcinosis, Raynauds phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias). Serum concentrations of C-reactive protein (CRP) were measured by immunoturbidimetry. The cells involved in PTX3 production in vivo were identified in skin biopsy samples. RESULTS Patients with active vasculitis had significantly higher concentrations of PTX3 than did those with quiescent disease (P < 0.001). PTX3 levels in the latter group were similar to those in healthy controls. PTX3 levels were higher in patients with untreated vasculitis and lower in patients who underwent immunosuppressive treatments (P < 0.005). In contrast, patients with active SLE had negligible levels of the pentraxin. PTX3 levels did not correlate with CRP levels in vasculitis patients. Endothelial cells produced PTX3 in active skin lesions. CONCLUSION PTX3 represents a novel acute-phase reactant produced at sites of active vasculitis.

Expression of monocyte chemotactic protein and interleukin-8 by cytokine-activated human vascular smooth muscle cells.

The present study was designed to investigate the capacity of human vascular smooth muscle cells (SMCs) to produce a cytokine chemotactic for monocytes (monocyte chemotactic protein [MCP]) and by way of comparison, a related polypeptide activator of neutrophils (known as interleukin-8 [IL-8] or neutrophil activating protein-1 [NAP-1]. On exposure to IL-1, SMCs released high levels of chemotactic activity for monocytes, which could be removed by absorption with anti-MCP antibodies. MCP production by activated SMCs was comparable to that of IL-1-stimulated umbilical vein endothelial cells. Activated SMCs released appreciable levels of IL-8, as determined by a specific enzyme-linked immunosorbent assay, but little chemotactic activity for neutrophils. IL-1-treated SMCs expressed high levels of both MCP and IL-8 mRNA transcripts, as assessed by Northern blot analysis. Tumor necrosis factor and bacterial lipopolysaccharide but not IL-6 also induced MCP and IL-8 gene expression in SMCs. Nuclear runoff analysis revealed that IL-1 augmented transcription of the MCP and IL-8 genes. The capacity of SMCs to produce a cytokine (MCP) that recruits and activates circulating mononuclear phagocytes may be of considerable importance in the pathogenesis of vascular diseases (e.g., vasculitis and atherosclerosis) that are characterized by monocyte infiltration of the vessel wall.

Production of the soluble pattern recognition receptor PTX3 by myeloid, but not plasmacytoid, dendritic cells

PTX3 is a prototypic of long pentraxin consisting of an N‐terminal portion coupled to a C‐terminal pentraxin domain, the latter related to short pentraxins (C‐reactive protein and serum amyloid P component). PTX3 is a soluble pattern recognition receptor, which plays a non‐redundant role in resistance against selected pathogens and in female fertility. The present study was designed to analyze the production of PTX3 by human dendritic cells (DC) and to define the role of different innate immunity receptors in its induction. Human monocyte‐derived DC produced copious amounts of PTX3in response to microbial ligands engaging different members of the Toll‐like receptor (TLR) family (TLR1 through TLR6), whereas engagement of the mannose receptor had no substantial effect. DC werebetter producers of PTX3 than monocytes and macrophages. Freshly isolated peripheral blood myeloid DC produced PTX3 in response to diverse microbial stimuli. In contrast, plasmacytoid DC exposed to influenza virus or to CpG oligodeoxynucleotides engaging TLR9, did not produce PTX3. PTX3‐expressing DC were present in inflammatory lymph nodes from HIV‐infected patients. These results suggest that DC of myelomonocytic origin are a major source of PTX3, a molecule which facilitates pathogen recognition and subsequent activation of innate and adaptive immunity.

Long Pentraxin PTX3 Upregulates Tissue Factor Expression in Human Endothelial Cells: A Novel Link Between Vascular Inflammation and Clotting Activation

Inflammation is a major contributing factor to atherosclerotic plaque development and ischemic heart disease. PTX3 is a long pentraxin that was recently found to be increased in patients with acute myocardial infarction. Because tissue factor (TF), the in vivo trigger of blood coagulation, plays a dominant role in thrombus formation after plaque rupture, we tested the possibility that PTX3 could modulate TF expression. Human umbilical vein endothelial cells, incubated with endotoxin (lipopolysaccharide) or the inflammatory cytokines interleukin-1&bgr; and tumor necrosis factor-&agr;, expressed TF. The presence of PTX3 increased TF activity and antigen severalfold in a dose-dependent fashion. PTX3 exerted its effect at the transcription level, inasmuch as the increased levels of TF mRNA, mediated by the stimuli, were enhanced in its presence. The increase in mRNA determined by PTX3 originated from an enhanced nuclear binding activity of the transacting factor c-Rel/p65, which was mediated by the agonists and measured by electrophoretic mobility shift assay. The mechanism underlying the increased c-Rel/p65 activity resided in an enhanced degradation of the c-Rel/p65 inhibitory protein I&kgr;B&agr;. In the area of vascular injury, during the inflammatory response, cell-mediated fibrin deposition takes place. Our results suggest that PTX3, by increasing TF expression, potentially plays a role in thrombogenesis and ischemic vascular disease.