Dual function of the long pentraxin PTX3 in resistance against pulmonary infection with Klebsiella pneumoniae in transgenic mice

Aberrant methylation of the 3q25 tumor suppressor gene PTX3 in human esophageal squamous cell carcinoma

AIM: To identify the novel methylation-silenced gene pentraxin 3 (PTX3) in esophageal squamous cell carcinoma (ESCC).

METHODS: PTX3 mRNA expression was examined in six human ESCC cell lines, one human immortalized normal esophageal epithelial cell line, primary ESCC tumor tissue, and paired adjacent nontumor tissue using reverse transcription polymerase chain reaction (RT-PCR). Semi-quantitative immunohistochemistry was used to examine cellular localisation and protein levels. Methylation specific PCR and bisulphite genomic sequencing were employed to investigate the methylation of the candidate gene.

RESULTS: In the majority of ESCC cell lines, we found that PTX3 expression was down-regulated due to gene promoter hypermethylation, which was further confirmed by bisulphite genomic sequencing. Demethylation treatment with 5-aza-2’-deoxycytidine restored PTX3 mRNA expression in ESCC cell lines. Methylation was more common in tumor tissues (85%) than in adjacent nontumor tissues (25%) (P < 0 .01).

CONCLUSION: PTX3 is down-regulated through promoter hypermethylation in ESCC, and could potentially serve as a biomarker of ESCC.

Pathogen recognition by the long pentraxin PTX3

Innate immunity represents the first line of defence against pathogens and plays key roles in 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 (PRMs) that recognise pathogen-associated molecular patterns (PAMPs) and initiate the immune response in coordination with the cellular arm, therefore acting as functional ancestors of antibodies. The long pentraxin PTX3 is a prototypic soluble PRM that is produced at sites of infection and inflammation by both somatic and immune cells. Gene targeting of this evolutionarily conserved protein has revealed a nonredundant role in resistance to selected pathogens. Moreover, PTX3 exerts important functions at the cross-road between innate immunity, inflammation, and female fertility. Here, we review the studies on PTX3, with emphasis on pathogen recognition and cross-talk with other components of the innate immune system.

The therapeutic potential of the humoral pattern recognition molecule PTX3 in chronic lung infection caused by Pseudomonas aeruginosa

Chronic lung infections by Pseudomonas aeruginosa strains are a major cause of morbidity and mortality in cystic fibrosis (CF) patients. Although there is no clear evidence for a primary defect in the immune system of CF patients, the host is generally unable to clear P. aeruginosa from the airways. PTX3 is a soluble pattern recognition receptor that plays nonredundant roles in the innate immune response to fungi, bacteria, and viruses. In particular, PTX3 deficiency is associated with increased susceptibility to P. aeruginosa lung infection. To address the potential therapeutic effect of PTX3 in P. aeruginosa lung infection, we established persistent and progressive infections in mice with the RP73 clinical strain RP73 isolated from a CF patient and treated them with recombinant human PTX3. The results indicated that PTX3 has a potential therapeutic effect in P. aeruginosa chronic lung infection by reducing lung colonization, proinflammatory cytokine levels (CXCL1, CXCL2, CCL2, and IL-1β), and leukocyte recruitment in the airways. In models of acute infections and in in vitro assays, the prophagocytic effect of PTX3 was maintained in C1q-deficient mice and was lost in C3- and Fc common γ-chain-deficient mice, suggesting that facilitated recognition and phagocytosis of pathogens through the interplay between complement and FcγRs are involved in the therapeutic effect mediated by PTX3. These data suggested that PTX3 is a potential therapeutic tool in chronic P. aeruginosa lung infections, such as those seen in CF patients.

High plasma level of long pentraxin 3 (PTX3) is associated with fatal disease in bacteremic patients: a prospective cohort study

Introduction

Long pentraxin 3 (PTX3) is an acute-phase protein secreted by various cells, including leukocytes and endothelial cells. Like C-reactive protein (CRP), it belongs to the pentraxin superfamily. Recent studies indicate that high levels of PTX3 may be associated with mortality in sepsis. The prognostic value of plasma PTX3 in bacteremic patients is unknown.

Methods

Plasma PTX3 levels were measured in 132 patients with bacteremia caused by Staphylococcus aureus, Streptococcus pneumoniae, β-hemolytic streptococcae and Escherichia coli, using a commercial solid-phase enzyme-linked immunosorbent assay (ELISA). Values were measured on days 1–4 after positive blood culture, on day 13–18 and on recovery.

Results

The maximum PTX3 values on days 1–4 were markedly higher in nonsurvivors compared to survivors (44.8 vs 6.4 ng/ml, p<0.001) and the AUC^ROC in the prediction of case fatality was 0.82 (95% CI 0.73–0.91). PTX3 at a cut-off level of 15 ng/ml showed 72% sensitivity and 81% specificity for fatal disease. High PTX3 (>15 ng/ml) was associated with hypotension (MAP <70 mmHg)(OR 7.9;95% CI 3.3–19.0) and high SOFA score (≥4)(OR 13.2; 95% CI 4.9–35.4). The CRP level (maximum value on days 1 to 4) did not predict case fatality at any cut-off level in the ROC curve (p = 0.132). High PTX3 (>15 ng/ml) remained an independent risk factor for case fatality in a logistic regression model adjusted for potential confounders.

Conclusions

PTX3 proved to be a specific independent prognostic biomarker in bacteremia. PTX3 during the first days after diagnosis showed better prognostic value as compared to CRP, a widely used biomarker in clinical settings. PTX3 measurement offers a novel opportunity for the prognostic stratification of bacteremia patients.

Adenosine deaminase inhibition prevents Clostridium difficile toxin A-induced enteritis in mice

Toxin A (TxA) is able to induce most of the classical features of Clostridium difficile-associated disease in animal models. The objective of this study was to determine the effect of an inhibitor of adenosine deaminase, EHNA [erythro-9-(2-hydroxy-3-nonyl)-adenine], on TxA-induced enteritis in C57BL6 mice and on the gene expression of adenosine receptors. EHNA (90 μmol/kg) or phosphate-buffered saline (PBS) was injected intraperitoneally (i.p.) 30 min prior to TxA (50 μg) or PBS injection into the ileal loop. A(2A) adenosine receptor agonist (ATL313; 5 nM) was injected in the ileal loop immediately before TxA (50 μg) in mice pretreated with EHNA. The animals were euthanized 3 h later. The changes in the tissue were assessed by the evaluation of ileal loop weight/length and secretion volume/length ratios, histological analysis, myeloperoxidase assay (MPO), the local expression of inducible nitric oxide synthase (NOS2), pentraxin 3 (PTX3), NF-κB, tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β) by immunohistochemistry and/or quantitative reverse transcription-PCR (qRT-PCR). The gene expression profiles of A₁, A(2A), A(2B), and A₃ adenosine receptors also were evaluated by qRT-PCR. Adenosine deaminase inhibition, by EHNA, reduced tissue injury, neutrophil infiltration, and the levels of proinflammatory cytokines (TNF-α and IL-1β) as well as the expression of NOS2, NF-κB, and PTX3 in the ileum of mice injected with TxA. ATL313 had no additional effect on EHNA action. TxA increased the gene expression of A₁ and A(2A) adenosine receptors. Our findings show that the inhibition of adenosine deaminase by EHNA can prevent Clostridium difficile TxA-induced damage and inflammation possibly through the A(2A) adenosine receptor, suggesting that the modulation of adenosine/adenosine deaminase represents an important tool in the management of C. difficile-induced disease.

Protective molecules and their cognate antibodies: new players in autoimmunity

Impairment of the clearance of apoptotic material seems to contribute to autoantigen exposure, which can initiate or maintain an autoimmune response in predisposed individuals. Complement component C1q, Creactive protein (CRP), serum amyloid P (SAP), mannose-binding lectin (MBL), apolipoprotein A-1 (Apo A-1) and long pentraxin 3 (PTX3) are molecules involved in the removal of apoptotic bodies and pathogens, and in other antiinflammatory pathways. For this reason they have been called "protective" molecules. C1q has a key role in the activation of the complement cascade and acts as a bridging molecule between apoptotic bodies and macrophages favouring phagocytosis. In addition to other functions, CRP, SAP and MBL bind to the surface of numerous pathogens as well as cellular debris and activate the complement cascade, thus stimulating their clearance by immune cells. The role of PTX3 is more controversial. In fact, PTX also promotes the clearance of microorganisms, but the activation of the complement cascade through C1q and removal of apoptotic material can be either stimulated or inhibited by this molecule. Antibodies against protective molecules have been recently reported in systemic lupus erythematosus and other autoimmune rheumatic diseases. Some of them seem to be pathogenetic and others protective. Thus, protective molecules and their cognate antibodies may constitute a regulatory network involved in autoimmunity. Dysregulation of this system might contribute to the development of autoimmune diseases in predisposed individuals.

Cigarette smoke induces PTX3 expression in pulmonary veins of mice in an IL-1 dependent manner

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with abnormal inflammatory responses and structural alterations of the airways, lung parenchyma and pulmonary vasculature. Since Pentraxin-3 (PTX3) is a tuner of inflammatory responses and is produced by endothelial and inflammatory cells upon stimuli such as interleukin-1β (IL-1β), we hypothesized that PTX3 is involved in COPD pathogenesis.

METHODS AND RESULTS

We evaluated whether cigarette smoke (CS) triggers pulmonary and systemic PTX3 expression in vivo in a murine model of COPD. Using immunohistochemical (IHC) staining, we observed PTX3 expression in endothelial cells of lung venules and veins but not in lung arteries, airways and parenchyma. Moreover, ELISA on lung homogenates and semi-quantitative scoring of IHC-stained sections revealed a significant upregulation of PTX3 upon subacute and chronic CS exposure. Interestingly, PTX3 expression was not enhanced upon subacute CS exposure in IL-1RI KO mice, suggesting that the IL-1 pathway is implicated in CS-induced expression of vascular PTX3. Serum PTX3 levels increased rapidly but transiently after acute CS exposure.To elucidate the functional role of PTX3 in CS-induced responses, we examined pulmonary inflammation, protease/antiprotease balance, emphysema and body weight changes in WT and Ptx3 KO mice. CS-induced pulmonary inflammation, peribronchial lymphoid aggregates, increase in MMP-12/TIMP-1 mRNA ratio, emphysema and failure to gain weight were not significantly different in Ptx3 KO mice compared to WT mice. In addition, Ptx3 deficiency did not affect the CS-induced alterations in the pulmonary (mRNA and protein) expression of VEGF-A and FGF-2, which are crucial regulators of angiogenesis.

CONCLUSIONS

CS increases pulmonary PTX3 expression in an IL-1 dependent manner. However, our results suggest that either PTX3 is not critical in CS-induced pulmonary inflammation, emphysema and body weight changes, or that its role can be fulfilled by other mediators with overlapping activities.

Role of complement and Fc{gamma} receptors in the protective activity of the long pentraxin PTX3 against Aspergillus fumigatus

Pentraxin 3 (PTX3) is a soluble pattern recognition molecule playing a nonredundant role in resistance against Aspergillus fumigatus. The present study was designed to investigate the molecular pathways involved in the opsonic activity of PTX3. The PTX3 N-terminal domain was responsible for conidia recognition, but the full-length molecule was necessary for opsonic activity. The PTX3-dependent pathway of enhanced neutrophil phagocytic activity involved complement activation via the alternative pathway; Fcγ receptor (FcγR) IIA/CD32 recognition of PTX3-sensitized conidia and complement receptor 3 (CR3) activation; and CR3 and CD32 localization to the phagocytic cup. Gene targeted mice (ptx3, FcR common γ chain, C3, C1q) validated the in vivo relevance of the pathway. In particular, the protective activity of exogenous PTX3 against A fumigatus was abolished in FcR common γ chain-deficient mice. Thus, the opsonic and antifungal activity of PTX3 is at the crossroad between complement, complement receptor 3-, and FcγR-mediated recognition. Because short pentraxins (eg, C-reactive protein) interact with complement and FcγR, the present results may have general significance for the mode of action of these components of the humoral arm of innate immunity.

An integrated view of humoral innate immunity: pentraxins as a paradigm

The innate immune system consists of a cellular and a humoral arm. Pentraxins (e.g., the short pentraxin C reactive protein and the long pentraxin PTX3) are key components of the humoral arm of innate immunity which also includes complement components, collectins, and ficolins. In response to microorganisms and tissue damage, neutrophils, macrophages, and dendritic cells are major sources of fluid-phase pattern-recognition molecules (PRMs) belonging to different molecular classes. Humoral PRMs in turn interact with and regulate cellular effectors. Effector mechanisms of the humoral innate immune system include activation and regulation of the complement cascade; agglutination and neutralization; facilitation of recognition via cellular receptors (opsonization); and regulation of inflammation. Thus, the humoral arm of innate immunity is an integrated system consisting of different molecules and sharing functional outputs with antibodies.

Persisting high levels of plasma pentraxin 3 over the first days after severe sepsis and septic shock onset are associated with mortality

PURPOSE

Pentraxin 3 (PTX3) is an inflammatory mediator produced by neutrophils, macrophages, myeloid dendritic and endothelial cells. During sepsis a massive inflammatory activation and coagulation/fibrinolysis dysfunction occur. PTX3, as a mediator of inflammation, may represent an early marker of severity and outcome in sepsis.

METHODS

This study is based on a prospective trial regarding the impact of glycemic control on coagulation in sepsis. Ninety patients admitted to three general intensive care units were enrolled when severe sepsis or septic shock was diagnosed. At enrollment, we recorded sepsis signs, disease severity, coagulation activation [prothrombin fragments 1 + 2 (F(1+2))] and fibrinolysis inhibition [plasminogen activator inhibitor-1 (PAI-1)]. We measured plasma PTX3 levels at enrollment, everyday until day 7, then at days 9, 11, 13, 18, 23 and 28. Mortality was recorded at day 90.

RESULTS

Although not different on day 1, PTX3 remained significantly higher in non-survivors than in survivors over the first 5 days (p = 0.002 by general linear model). On day 1, PTX3 levels were higher in septic shock than in severely septic patients (p = 0.029). Day 1 PTX3 was significantly correlated with platelet count (p < 0.001), SAPS II score (p = 0.006) and SOFA score (p < 0.001). Day 1 PTX3 was correlated with F(1+2) concentration and with PAI-1 activity and concentration (p < 0.05 for all).

CONCLUSIONS

Persisting high levels of circulating PTX3 over the first days from sepsis onset may be associated with mortality. PTX3 correlates with severity of sepsis and with sepsis-associated coagulation/fibrinolysis dysfunction.

The long pentraxin PTX3 as a prototypic humoral pattern recognition receptor: interplay with cellular innate immunity

The innate immune system consists of a cellular arm and a humoral arm. Components of humoral immunity include diverse molecular families, which represent functional ancestors of antibodies. They play a key role as effectors and modulators of innate resistance in animals and humans, interacting with cellular innate immunity. The prototypic long pentraxin, pentraxin 3 (PTX3), represents a case in point of this interplay. Gene targeting of this evolutionarily conserved long pentraxin has unequivocally defined its role at the crossroads of innate immunity, inflammation, matrix deposition, and female fertility. Phagocytes represent a key source of this fluid-phase pattern recognition receptor, which, in turn, facilitates microbial recognition by phagocytes acting as an opsonin. Moreover, PTX3 has modulatory functions on innate immunity and inflammation. Here, we review the studies on PTX3 which emphasize the complexity and complementarity of the crosstalk between the cellular and humoral arms of innate immunity.

Coregulation in human leukocytes of the long pentraxin PTX3 and TSG-6

The prototypic long PTX3 is a multifunctional protein involved in innate resistance to pathogens and in controlling inflammation. TSG-6 is a hyaluronan-binding protein that is involved in ECM remodeling and has anti-inflammatory and chondroprotective functions. PTX3 and TSG-6 are coregulated by growth differentiation factor-9 in granulosa cells, where they are produced during the periovulatory period and play essential roles in the incorporation of hyaluronan into the ECM during cumulus expansion. The present study was designed to assess whether PTX3 and TSG-6 are coregulated in leukocytes, in particular, in phagocytes and DC. Monocytes, macrophages, and myeloid DC were found to produce high levels of TSG-6 and PTX3 in response to proinflammatory mediators (LPS or cytokines). Unstimulated neutrophil polymorphonuclear granulocytes expressed high levels of TSG-6 mRNA, but not PTX3 transcript, and stored both proteins in granules. In contrast, endothelial cells expressed substantial amounts of PTX3 mRNA and low levels of TSG-6 transcript under the conditions tested. Anti-inflammatory cytokines, such as IL-4, dampened LPS-induced TSG-6 and PTX3 expression. Divergent effects were observed with IL-10, which synergizes with TLR-mediated PTX3 induction but inhibits LPS-induced TSG-6 transcription. Immunohistochemical analysis confirms the colocalization of the two proteins in inflammatory infiltrates and in endothelial cells of inflamed tissues. Thus, here we show that myelomonocytic cells and MoDC are a major source of TSG-6 and that PTX3 and TSG-6 are coregulated under most of the conditions tested. The coordinated expression of PTX3 and TSG-6 may play a role in ECM remodeling at sites of inflammation.

The long pentraxin PTX3 is crucial for tissue inflammation after intestinal ischemia and reperfusion in mice

The pentraxin superfamily is a group of evolutionarily conserved proteins that play important roles in the immune system. The long pentraxin PTX3 protein was originally described as able to be induced by pro-inflammatory stimuli in a variety of cell types. In this study, we evaluated the phenotype of Ptx3(-/-) mice subjected to ischemia followed by reperfusion of the superior mesenteric artery. In reperfused wild-type mice, there was significant local and remote injury as demonstrated by increases in vascular permeability, neutrophil influx, nuclear factor-kappaB activation, and production of CXCL1 and tumor necrosis factor-alpha. PTX3 levels were elevated in both serum and intestine after reperfusion. In Ptx3(-/-) mice, local and remote tissue injury was inhibited, and there were decreased nuclear factor-kappaB translocation and cytokine production. Intestinal architecture was preserved, and there were decreased neutrophil influx and significant prevention of lethality in Ptx3(-/-) mice as well. PTX3 given intravenously before reperfusion reversed the protection observed in Ptx3(-/-) mice in a dose-dependent manner, and PTX3 administration significantly worsened tissue injury and lethality in wild-type mice. In conclusion, our studies demonstrate a major role for PTX3 in determining acute reperfusion-associated inflammation, tissue injury, and lethality and suggest the soluble form of this molecule is active in this system. Therapeutic blockade of PTX3 action may be useful in the control of the injuries associated with severe ischemia and reperfusion syndromes.

Pentraxins: multifunctional proteins at the interface of innate immunity and inflammation

Pentraxins are a family of multimeric pattern recognition proteins highly conserved in evolution. On the basis of the primary structure of the protomer, pentraxins are divided into two groups: short pentraxins and long pentraxins. C reactive protein, the first pattern recognition receptor identified, and serum amyloid P component are classic short pentraxins produced in the liver in response to IL-6. Long pentraxins, including the prototype PTX3, are expressed in a variety of tissues. PTX3 is produced by a variety of cells and tissues, most notably dendritic cells and macrophages, in response to Toll-like receptor (TLR) engagement and inflammatory cytokines. Through interaction with several ligands, including selected pathogens and apoptotic cells, pentraxins play a role in complement activation, pathogen recognition and apoptotic cell clearance. In addition, PTX3 is involved in the deposition of extracellular matrix and female fertility. Unlike the classic short pentraxins CRP and SAP, PTX3 primary sequence and regulation are highly conserved in man and mouse. Thus, gene targeting identified PTX3 (and presumably other members of the family) as multifunctional soluble pattern recognition receptors acting as a nonredundant component of the humoral arm of innate immunity and involved in tuning inflammation, matrix deposition, and female fertility. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.

Role of the chemokine receptor CXCR2 in bleomycin-induced pulmonary inflammation and fibrosis

Pulmonary fibrosis is characterized by chronic inflammation and excessive collagen deposition. Neutrophils are thought to be involved in the pathogenesis of lung fibrosis. We hypothesized that CXCR2-mediated neutrophil recruitment is essential for the cascade of events leading to bleomycin-induced pulmonary fibrosis. CXCL1/KC was detected as early as 6 hours after bleomycin instillation and returned to basal levels after Day 8. Neutrophils were detected in bronchoalveolar lavage and interstitium from 12 hours and peaked at Day 8 after instillation. Treatment with the CXCR2 receptor antagonist, DF2162, reduced airway neutrophil transmigration but led to an increase of neutrophils in lung parenchyma. There was a significant reduction in IL-13, IL-10, CCL5/RANTES, and active transforming growth factor (TGF)-beta(1) levels, but not on IFN-gamma and total TGF-beta(1,) and enhanced granulocyte macrophage-colony-stimulating factor production in DF2162-treated animals. Notably, treatment with the CXCR2 antagonist led to an improvement of the lung pathology and reduced collagen deposition. Using a therapeutic schedule, DF2162 administered from Days 8 to 16 after bleomycin reduced pulmonary fibrosis and levels of active TGF-beta(1) and IL-13. DF2162 treatment reduced bleomycin-induced expression of von Willebrand Factor, a marker of angiogenesis, in the lung. In vitro, DF2162 reduced the angiogenic activity of IL-8 on human umbilical vein endothelial cells. In conclusion, we show that CXCR2 plays an important role in mediating fibrosis after bleomycin instillation. The compound blocks angiogenesis and the production of pro-angiogenic cytokines, and decreases IL-8-induced endothelial cell activation. An effect on neutrophils does not appear to account for the major effects of the blockade of CXCR2 in the system.

Pentraxin 3 in acute respiratory distress syndrome: an early marker of severity

OBJECTIVE

Pentraxin 3 is a fluid phase receptor involved in innate immunity. It belongs to the Pentraxins family, as C-reactive protein does. Pentraxin 3 is produced by a variety of tissue cells, whereas only the liver produces C-reactive protein. Pentraxin 3 plays a unique role in the regulation of inflammation. Acute lung injury and acute respiratory distress syndrome are characterized by an important inflammatory reaction. We investigated the role of pentraxin 3 as a marker of severity and outcome predictor of acute lung injury and acute respiratory distress syndrome.

DESIGN

We measured circulating pentraxin 3 and C-reactive protein levels within 24 hrs from intubation (day 1), after 24 hrs from the first sample, then every 3 days for the first month and then once a week, until discharge from the intensive care unit. Pentraxin 3 was also measured in bronchoalveolar lavages, performed when clinically indicated.

SETTING

One university medical center general intensive care unit.

PATIENTS

The study included 21 patients affected by acute lung injury and acute respiratory distress syndrome (1994 Consensus Conference criteria).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pentraxin 3 plasma levels were high with a peak on the first day (median 71.05 ng/mL, interquartile range 52.37-117.38 ng/mL, normal values <2 ng/mL), declining thereafter. C-reactive protein peaked later and remained at relatively high values. Out of several day 1 parameters, pentraxin 3 was the only significant difference between survivors and nonsurvivors. Pentraxin 3 levels were positively correlated with lung injury score values (p < 0.001) and number of organ failures (p < 0.001). Pentraxin 3 was present in bronchoalveolar lavages fluids (5.03 ng/mL, interquartile range 1.52-8.48 ng/mL) and bronchoalveolar lavages positive to bacterial culture were associated with significantly higher pentraxin 3 values (p < 0.05).

CONCLUSIONS

The results presented here show that pentraxin 3 is elevated in acute lung injury and acute respiratory distress syndrome and that its levels correlate with parameters of lung injury and systemic involvement. The clinical and pathophysiological significance of pentraxin 3 in acute lung injury and acute respiratory distress syndrome deserves further scrutiny.

Antiviral activity of the long chain pentraxin PTX3 against influenza viruses

Proteins of the innate immune system can act as natural inhibitors of influenza virus, limiting growth and spread of the virus in the early stages of infection before the induction of adaptive immune responses. In this study, we identify the long pentraxin PTX3 as a potent innate inhibitor of influenza viruses both in vitro and in vivo. Human and murine PTX3 bound to influenza virus and mediated a range of antiviral activities, including inhibition of hemagglutination, neutralization of virus infectivity and inhibition of viral neuraminidase. Antiviral activity was associated with binding of the viral hemagglutinin glycoprotein to sialylated ligands present on PTX3. Using a mouse model we found PTX3 to be rapidly induced following influenza infection and that PTX3-/- mice were more susceptible than wild-type mice to infection by PTX3-sensitive virus strains. Therapeutic treatment of mice with human PTX3 promoted survival and reduced viral load in the lungs following infection with PTX3-sensitive, but not PTX3-resistant, influenza viruses. Together, these studies describe a novel antiviral role for PTX3 in early host defense against influenza infections both in vitro and in vivo and describe the therapeutic potential of PTX3 in ameliorating disease during influenza infection.

The long pentraxin 3 and its role in autoimmunity

OBJECTIVES

To review the physiological and physiopathological roles of pentraxin 3 (PTX3), focusing on autoimmunity and vascular pathology.

METHODS

A systematic literature review using the keywords "pentraxin 3," "innate immunity," "apoptosis," "autoimmunity," and "endothelial dysfunction" from 1990 to 2007 was performed. All relevant articles and pertinent secondary references in English were reviewed.

RESULTS

PTX3 has a large number of multiple functions in different contexts. PTX3 plays an important role in innate immunity, inflammation, vascular integrity, fertility, pregnancy, and also in the central nervous system. In innate immunity, its normal function is to increase the immune response to selected pathogens while also exerting control over potential autoimmune reactions. It maintains a tightly homeostatic equilibrium in the local immune microenvironment by avoiding an exaggerated immune response and controlling peripheral tolerance to self-antigens. In contrast, in some autoimmune diseases, PTX3 appears to be involved in the development of autoimmune phenomena. A possible explanation for these apparent paradoxical functions may be related to the highly polymorphic PTX3 gene.

CONCLUSION

PTX3 is physiologically a protective molecule. However, in several autoimmune diseases PTX3 appears to facilitate the development of autoimmunity. The PTX3 gene could influence the development of autoimmune reactions and vascular involvement in human pathology.

Pentraxins in innate immunity: from C-reactive protein to the long pentraxin PTX3

Pentraxins are a family of multimeric pattern-recognition proteins highly conserved in evolution. Based on the primary structure of the subunit, the pentraxins are divided into two groups: short pentraxins and long pentraxins. C-reactive protein and serum amyloid P-component are classic short pentraxins produced in the liver, whereas the prototype of the long pentraxin family is PTX3. Innate immunity cells and vascular cells produce PTX3 in response to proinflammatory signals and Toll-like receptor engagement. PTX3 interacts with several ligands, including growth factors, extracellular matrix components, and selected pathogens, playing a role in complement activation, facilitating pathogen recognition, and acting as a predecessor of antibodies. In addition, PTX3 is essential in female fertility acting on the assembly of the cumulus oophorus extracellular matrix. Thus, PTX3 is a multifunctional soluble pattern recognition receptor acting as a nonredundant component of the humoral arm of innate immunity and involved in tuning inflammation, in matrix deposition and female fertility. Evidence suggests that PTX3 is a useful new serological marker, rapidly reflecting tissue inflammation and damage under diverse clinical conditions.

Platelet activating factor receptors drive CXC chemokine production, neutrophil influx and edema formation in the lungs of mice injected with Tityus serrulatus venom

Lung injury is a common finding and a frequent cause of death in cases of severe human envenoming by scorpion sting. The present work investigated the effects of pretreatment with a platelet activation factor receptor (PAFR) antagonist and a CXCR2 inhibitor on the lung injury induced by subcutaneous injection of Tityus serrulatus venom (TsV) in mice. Lung injury was assessed by evaluating the extravasation of Evans blue dye, as an index of increased vascular permeability, the neutrophil accumulation (mieloperoxidase activity), the concentration of tumor necrosis factor-alpha (TNF-alpha) and the chemokine KC in the lung after TsV administration. Neutrophil influx was preceded by the production of KC and dependent on CXCR2, as shown by the ability of repertaxin, a CXCR2 inhibitor, to prevent an increase of MPO activity in the lung. Repertaxin had no effect on TsV-induced lethality. The PAFR antagonist (UK-74,505) significantly reduced TsV-induced vascular permeability changes and neutrophil influx in the lungs. The inhibition of neutrophil influx was associated with inhibition of the production of the CXCR2-active chemokine KC. UK-74,505 had no effect on the lethality induced by TsV. In conclusion, these results show that the influx of neutrophils in the lungs of mice injected with TsV is dependent on the activation of PAFR and on PAFR-dependent production of the chemokine KC as well as activation of CXCR2 on neutrophils. Although lung injury may contribute to late lethality after TsV envenoming, acute lethality is not modified by inhibitors of neutrophil influx.

Long pentraxin 3 in pulmonary infection and acute lung injury

Long pentraxin 3 (PTX3) is a newly discovered acute phase protein produced at the sites of infection and inflammation by tissue cells, macrophages, monocytes, and dendritic cells. PTX3 plays an important role in preventing infection of certain fungi, bacteria, and viruses in the lung. Recombinant PTX3 has been proposed as a potential antifungal molecule for therapy. However, under certain experimental conditions, such as intestinal ischemia-reperfusion, high volume mechanical ventilation, or severe bacterial infection, increased expression of PTX3 is associated with more severe lung injury. Therefore, it is necessary to further explore the sources of PTX3 in the lung and the regulatory mechanisms of its expression. It is also essential to further determine how PTX3 binds to pathogens, complement, and apoptotic cells, and to determine whether PTX3 has a specific receptor in targeted cells. These studies will provide insight into the pathological processes of pulmonary infection and acute lung injury and provide potential novel therapeutic strategies to control pulmonary infections without severe lung injury.