TLR3 preconditioning induces anti-inflammatory and anti-ictogenic effects in mice mediated by the IRF3/IFN-ß axis.

Activation of Toll-like receptor 3 (TLR3) was previously shown to contribute to the generation of epileptic seizures in rodents by evoking a proinflammatory response in the forebrain. This suggests that TLR3 blockade may provide therapeutic effects in epilepsy. We report that brain activation of TLR3 using the synthetic receptor ligand Poly I:C may also result in remarkable dose- and time-dependent inhibitory effects on acute seizures in mice without inducing inflammation. These inhibitory effects are associated with reduced neuronal excitability in the hippocampus as shown by a decrease in the population spike amplitude of CA1 pyramidal neurons following Schaffer collaterals stimulation. TLR3 activation which results in seizure inhibition does not evoke NF-kB-dependent inflammatory molecules or morphological activation of glia, however, it induces the alternative interferon (IFN) regulatory factor (IRF)-3/IFN-ß signaling pathway. IFN-ß reproduced the inhibitory effects of Poly I:C on neuronal excitability in hippocampal slices. Seizure inhibition attained with activation the TLR3-IRF3/IFN-ß axis should be carefully considered when TLR3 are targeted for therapeutic purposes.

Pro-inflammatory M1/Th1 type immune network and increased expression of TSG-6 in the eutopic endometrium from women with endometriosis.

OBJECTIVE: The study aimed to explore the type 1 and type 2 cytokines expression in the endometrium from women affected by endometriosis compared to controls. The expression of TSG-6, a multifunctional protein involved in several inflammatory disease, was also evaluated. Study Design SETTING: Experimental clinical study. PATIENTS: 10 patients affected by endometriosis and 11 controls. INTERVENTIONS: Patients underwent to an ultrasound transvaginal examination and a diagnostic hysteroscopy in order to exclude any uterine abnormality. All patients underwent endometrial biopsy using a Novak's curette. MAIN OUTCOME MEASURES: The endometrial expression of type 1 (IL- 1 ß TNF-α, IL-8) and type 2 (IL-10) cytokines, and of TSG-6 was evaluated by immunohistochemistry and by real time PCR. The expression of TSG-6 was confirmed by western blot. RESULTS: Results of PCR analysis and of immunohistochemistry revealed an increased expression of IL-1ß, TNF-α, IL-8 and of TSG-6 in the endometrium of endometriosic patients. IL-10 expression did not show any difference. CONCLUSIONS: An increased expression of pro-inflammatory type 1 cytokines was demonstrated in the endometrium from endometriosic patients, suggesting an endometrial environment harmful for implantation due to the prevalence of Th1 related immunity. An increased expression of TSG-6 was also demonstrated for the first time. Our findings concur to better define the inflammatory imbalance and the abnormal endometrial receptivity, reported in literature, of the eutopic endometrium of women affected by endometriosis.

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.

PTX3 as a potential endothelial dysfunction biomarker for severity of preeclampsia and IUGR.

Endothelial dysfunction typical of preeclampsia (PE) is the result of an excessive maternal inflammatory response to pregnancy. We investigated PTX3 in maternal, fetal and placental compartments in complicated pregnancies. Maternal blood samples were collected during the third trimester in 53 PE, 43 IUGR (intrauterine growth restriction) and 50 normal pregnancies. Fetal samples were collected from the umbilical vein in 26 PE, 23 IUGR and 26 normal pregnancies at elective cesarean section. Pattern and site of expression of PTX3 were studied by immunohistochemistry (IHC) on placenta, decidual bed and maternal peritoneum. PE and IUGR pregnancies had significantly higher maternal PTX3 levels compared to normal pregnancies, with IUGR significantly lower than PE. Maternal peritoneum expressed a significantly higher signal in the endothelium of pathological compared to normal pregnancies. The maternal increase of PTX3 correlated with the severity of disease with higher PTX3 concentrations in severe PE. Increased PTX3 levels in PE and IUGR mothers, together with IHC data represent the expression of altered endothelial function on the maternal side. IUGR fetuses had higher PTX3 values than controls and the increase was related to IUGR severity, likely reflecting the hypoxic environment. These data confirm the relevance of PTX3 in support the hypothesis that PE is a disease associated with altered maternal endothelial function. The PTX3 increase in IUGR fetuses deserves further investigation.

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.

PTX3 genetic variations affect the risk of Pseudomonas aeruginosa airway colonization in cystic fibrosis patients.

Cystic fibrosis (CF) is a common life-threatening autosomal recessive disorder in the Caucasian population, and the gene responsible is the CF transmembrane conductance regulator (CFTR). Patients with CF have repeated bacterial infection of the airways caused by Pseudomonas aeruginosa (PA), which is one of the predominant pathogen, and endobronchial chronic infection represents a major cause of morbidity and mortality. Pentraxin 3 (PTX3) is a gene that encodes the antimicrobial protein, PTX3, which is believed to have an important role in innate immunity of lung. To address the role of PTX3 in the risk of PA lung colonization, we investigated five single nucleotide polymorphisms of PTX3 gene in 172 Caucasian CF patients who were homozygous for the F508del mutation. We observed that PTX3 haplotype frequencies were significantly different between patients with PA colonization, as compared with noncolonized patients. Moreover, a protective effect was found in association with a specific haplotype (odds ratio 0.524). Our data suggest that variations within PTX3 affect lung colonization of Pseudomonas in patients with CF.

Evidence for a DC-specific inhibitory mechanism that depends on MyD88 and SIGIRR.

Dendritic cells (DC) are an essential link between the innate and adaptive immune response. To become effective antigen-presenting cells DC need to undergo maturation, during which they up-regulate co-stimulatory molecules and produce cytokines. There is great interest in utilizing DC in vaccination regimes. Over recent years, Toll-like receptor (TLR) signalling has been recognized to be one of the major inducers of DC maturation. This study describes a mutant version of the TLR adaptor molecule MyD88 (termed MyD88lpr) as a novel adjuvant for vaccination regimes. MyD88lpr specifically activates DC by disrupting a DC intrinsic inhibitory mechanism, which is dependent on single immunoglobulin IL-1R-related. Moreover, MyD88lpr was able to induce an IgG2a-dominated response to a co-expressed antigen, suggesting Th1 immunity. However, when used as a vaccine adjuvant for Influenza nucleoprotein there was no significant difference in the lung viral titres during the infection. This study describes MyD88lpr as a potential adjuvant for vaccinations, which would be able to target DC specifically.

Serum levels of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) and pentraxin 3 (PTX3) as markers of infection in febrile patients with systemic lupus erythematosus.

OBJECTIVE: To investigate the role of sTREM-1 and PTX3 as markers of infection in febrile patients with SLE. METHODS: In febrile (body temperature > or =38 degrees C) patients with SLE, blood samples of day 0, 1, 2, and 14 after presentation were drawn and relevant clinical data were collected. The patients were allocated to an infection group (n=19) or disease flare group (n=14). Serum levels of sTREM-1 and PTX3 were measured by ELISA using the serum samples of SLE patients and age- and sex-matched healthy controls (n=31). RESULTS: A total of 33 febrile episodes occurred in 32 SLE patients (19 infections, 14 flares) were studied. sTREM-1 levels on day 0 were significantly higher in the infection group than in the flare group (109.9 pg/ml (median) vs. 48.0 pg/ml, p=0.002), but PTX3 levels were similar in these two groups. The difference of sTREM-1 levels between infection group and flare group was persistent on day 1 and 2 (day 1, p=0.007; day 2, p=0.034). The highest diagnostic value (sensitivity=1.0, specificity=0.664) of sTREM-1 was obtained at the threshold value of 53.2 pg/mL. CONCLUSION: Serum sTREM-1 levels were significantly higher in the infection group than in the flare group of febrile SLE patients. Our findings suggest that serum sTREM-1 levels could be used to determine whether SLE patients have contracted an infection.

Inflammatory reaction and implantation: the new entries PTX3 and D6.

Successful embryonic implantation implies anchoring the conceptus in the maternal uterine wall, establishing a vascular supply to enable optimal growth and development of the conceptus, and promoting tolerance of fetal alloantigens encoded by paternal genes. To achieve these goals, complex molecular dialogues take place among the maternal endometrium, the conceptus, and the placenta. Several factors are involved in the fetal-maternal interaction, including hormones, growth factors, cytokines, chemokines, adhesion molecules, extracellular matrix components, and matrix-degrading enzymes. This complex cross-talk results in the induction of a local inflammatory response and a state of systemic inflammation, as revealed by leukocytosis, endothelium activation, increased activity of innate immune cells, and increased levels of inflammatory cytokines and chemokines. The enriched cytokine milieu associated to implantation is likely to control trophoblast migration and differentiation, leukocyte influx and activation, complement activation, as well as angiogenic and angiostatic processes in the implantation site. Finally, these mediators play a key role in tuning the immune responses to protect the fetus from infections as well as from maternal rejection. Here, the role of pro-inflammatory networks activated in implantation will be discussed. In particular, emphasis will be put on two new players involved in regulating inflammation at the maternal-fetal interface: the long pentraxin PTX3 and the decoy receptor for inflammatory chemokines D6.

Different roles of TiR8/Sigirr on toll-like receptor signaling in intrarenal antigen-presenting cells and tubular epithelial cells.

Toll-like receptors (TLRs) exist on both myeloid and intrinsic renal cells contributing to the initiation of innate immunity during renal infection with uropathogenic Escherichia coli. Toll-interleukin 1 receptor (IL-1R) (TIR)8/SIGIRR is an orphan receptor of the TLR/IL-1R family, which suppresses TLR signaling of immune cells and is highly expressed in the kidney. Lack of TIR8/SIGIRR is associated with enhanced renal chemokine signaling upon exposure to lipopolysaccharide (LPS). This was because of TIR8/SIGIRR expression on resident intrarenal myeloid cells rather than tubular epithelial cells which express it on basolateral and luminal membranes. The lack of TIR8/SIGIRR does not enhance TLR/IL-1R signaling in tubular epithelial cells as was observed in monocytes. TIR8/SIGIRR is induced in monocytes treated with LPS or tumor necrosis factor and interferon-gamma in a dose-dependent manner but was downregulated in treated tubule epithelial cells. This cell type-specific regulation and function did not relate to mRNA splice variants but was associated with N- and O-glycosylation of the receptor in renal cells of myeloid and nonmyeloid origin. Our studies show that resident myeloid cells contribute to TLR-mediated antimicrobial immunity in the kidney and that this function is controlled by Tir8/sigirr. TIR8/SIGIRR does not suppress TLR signaling in tubular epithelial cells, which supports their role as sensors of microbial infection in the kidney.

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.

Macrophage control of inflammation: negative pathways of regulation of inflammatory cytokines.

The recruitment of leukocytes from the blood compartment constitutes a multistep process which involves primary and secondary inflammatory cytokines, as well as adhesion molecules expressed on leukocytes and endothelial cells. The properties of the interleukin (IL)-1 system and of chemokines, as well as their interplay, are analysed. These mediators offer new paradigms to understand diverse pathologies, and provide tools and targets for the development of novel therapeutic strategies.

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)

Central role for G protein-coupled phosphoinositide 3-kinase gamma in inflammation.

Phosphoinositide 3-kinase (PI3K) activity is crucial for leukocyte function, but the roles of the four receptor-activated isoforms are unclear. Mice lacking heterotrimeric guanine nucleotide-binding protein (G protein)-coupled PI3Kgamma were viable and had fully differentiated neutrophils and macrophages. Chemoattractant-stimulated PI3Kgamma-/- neutrophils did not produce phosphatidylinositol 3,4,5-trisphosphate, did not activate protein kinase B, and displayed impaired respiratory burst and motility. Peritoneal PI3Kgamma-null macrophages showed a reduced migration toward a wide range of chemotactic stimuli and a severely defective accumulation in a septic peritonitis model. These results demonstrate that PI3Kgamma is a crucial signaling molecule required for macrophage accumulation in inflammation.

Antibody against murine PECAM-1 inhibits tumor angiogenesis in mice.

Platelet endothelial cell adhesion molecule (PECAM-1/CD31), a member of the immunoglobulin superfamily expressed at high levels on endothelial cells, has been recently implicated in angiogenesis. Although antagonism of PECAM-1 inhibited neovascularization in two different animal models of growth factor/chemokine-induced angiogenesis, its participation in tumor angiogenesis has not been established. We therefore investigated its involvement in models of tumor angiogenesis in mice. An antibody against murine PECAM-1 that was shown to block in vitro murine endothelial tube formation inhibited the subcutaneous growth and tumor vascularity of three tumors in mice: A549 human non-small cell lung cancer in SCID mice, B16 murine melanoma in C57BL/6 mice and AB12 murine mesothelioma in Balb/c mice. These studies suggest a possible role for PECAM-1 in the complex process of tumor angiogenesis and provide additional evidence of the importance of endothelial cell adhesion molecules to the formation of new vessels.