Globular adiponectin induces platelet activation through the collagen receptor GPVI-Fc receptor gamma chain complex.

We identify gAd as a novel ligand for GPVI that stimulates tyrosine kinase-dependent platelet aggregation. Our data raise the possibility that gAd may promote unwanted platelet activation at sites of vascular injury.

Protease-activated Receptor-2 (PAR(2)) in Human Periodontitis

No evidence for the role of protease-activated receptor-2 (PAR(2)) in human periodontal disease has been demonstrated so far. Thus, we sought to investigate the expression of PAR(2) mRNA in chronic periodontitis, and to examine whether its expression is related to the presence of PAR(2) potential activators. Microbiological and gingival crevicular fluid samples were collected from individuals with chronic periodontitis and control individuals, and the presence of neutrophil serine proteinase 3 (P3) and Porphyromonas gingivalis was evaluated. PAR(2) mRNA expression was higher (p < 0.001) in those with chronic periodontitis compared with control individuals, and it was statistically decreased (p = 0.0006) after periodontal treatment. Furthermore, those with chronic periodontitis presented higher (p < 0.05) levels of IL-1 alpha, IL-6, IL-8, and TNF-alpha, total proteolytic activity, P. gingivalis prevalence, and P3mRNA expression compared with control individuals. We conclude that PAR(2) mRNA expression and its potential activators are elevated in human chronic periodontitis, therefore suggesting that PAR(2) may play a role in periodontal inflammation.

Effects of 15-deoxy-Delta(12, 14) prostaglandin J(2) and ciglitazone on human cancer cell cycle progression and death: The role of PPAR gamma

The role of PPAR-gamma in ciglitazone and 15-d PGJ(2)-induced apoptosis and cell cycle arrest of Jurkat (before and after PPAR gamma gene silencing), U937 (express high levels of PPAR gamma) and HeLa (that express very low levels of PPAR gamma) cells was investigated. PPAR gamma gene silencing, per se, induced a G2/M cell arrest, loss of membrane integrity and DNA fragmentation of Jurkat cells, indicating that PPAR gamma is important for this cell survival and proliferation. Ciglitazone-induced apoptosis was abolished after knockdown of PPAR gamma suggesting a PPAR gamma-dependent pro-apoptotic effect. However, ciglitazone treatment was toxic for U937 and HeLa cells regardless of the presence of PPAR gamma. This treatment did not change the cell cycle distribution corroborating with a PPAR gamma-independent mechanism. On the other hand, 15-d PGJ(2) induced apoptosis of the three cancer cell lines regardless of the expression of PPAR gamma. These results suggest that PPAR gamma plays an important role for death of malignant T lymphocytes (Jurkat cells) and PPAR gamma agonists exert their effects through PPAR gamma-dependent and -independent mechanisms depending on the drug and the cell type. (C) 2007 Elsevier B.V. All rights reserved.

Role of PPAR-gamma in the Modulation of CD36 and FcgammaRII induced by LDL with Low and High Degrees of Oxidation During the Differentiation of the Monocytic THP-1 Cell Line

Scavenger or Fc gamma receptors are important for capture and clearance of modified LDL particles by monocytes/macrophages. Uptake via scavenger receptors is not regulated by intracellular levels of cholesterol and in consequence, macrophages develop into foam cells in the arterial intima. The levels of scavenger receptor CD36 are increased in atherosclerotic lesions and there is evidence that some components of oxLDL auto-regulate the expression of this receptor. Fc gamma receptor expression is increased in cardiovascular diseases but it is not known weather their expression is regulated by oxLDL. The biological properties of oxLDLs vary depending on the degree of oxidation. In the present study we investigated the effect of LDL particles showing extensive or low oxidation (HoxLDL and LoxLDL) on the expression of CD36 and Fc gamma RII in a human monocytic cell line (THP-1), differentiated or not to macrophage, and the involvement of PPAR gamma. It was found that both forms of oxLDL are able to increase the expression of CD36 and Fc gamma RII and that this effect is dependent on the degree of oxidation and of the stage of cell differentiation ( monocyte or macrophage). We also showed that the increased expression of Fc gamma RII is dependent on PPAR. whereas that of the CD36 is independent of PPAR gamma. Copyright (c) 2008 S. Karger AG, Basel

Endurance training activates AMP-activated protein kinase, increases expression of uncoupling protein 2 and reduces insulin secretion from rat pancreatic islets

Endurance exercise is known to enhance peripheral insulin sensitivity and reduce insulin secretion. However, it is unknown whether the latter effect is due to the reduction in plasma substrate availability or alterations in beta-cell secretory machinery. Here, we tested the hypothesis that endurance exercise reduces insulin secretion by altering the intracellular energy-sensitive AMP-activated kinase (AMPK) signaling pathway. Male Wistar rats were submitted to endurance protocol training one, three, or five times per week, over 8 weeks. After that, pancreatic islets were isolated, and glucose-induced insulin secretion (GIIS), glucose transporter 2 (GLUT2) protein content, total and phosphorylated calmodulin kinase kinase (CaMKII), and AMPK levels as well as peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1 alpha) and uncoupling protein 2 (UCP2) content were measured. After 8 weeks, chronic endurance exercise reduced GIIS in a dose-response manner proportionally to weekly exercise frequency. Contrariwise, increases in GLUT2 protein content, CaMKII and AMPK phosphorylation levels were observed. These alterations were accompanied by an increase in UCP2 content, probably mediated by an enhancement in PGC-1 alpha protein expression. In conclusion, chronic endurance exercise induces adaptations in beta-cells leading to a reduction in GIIS, probably by activating the AMPK signaling pathway. Journal of Endocrinology (2011) 208, 257-264

Structural requirement for PPAR gamma binding revealed by a meta analysis of holo-crystal structures

PPAR gamma is a ligand regulated transcriptional factor that modulates the transcription of several genes involved in fat and sugar metabolism. Due to its easy bacterial expression and crystallization, several crystal structures of holo-PPAR gamma have been reported and deposited in the Protein Data Bank. Here, we investigated the three-dimensional electrostatic properties of 55 PPAR gamma ligands and used this information for clustering them through principal component analysis. We found out that, according to their electrostatic potential, these ligands can be separated in three groups, with different binding features. We also observed that non-selective and selective ligands show different 3D electrostatic properties and are separated in different clusters. The relevance of this analysis for the development of new binders is discussed. (C) 2010 Elsevier Masson SAS. All rights reserved.

Role of protease-activated receptor-2 in inflammation, and its possible implications as a putative mediator of periodontitis

Proteinase-activated receptor-2 (PAR2) belongs to a novel subfamily of G-protein-coupled receptors with seven-transmembrane domains. This receptor is widely distributed throughout the body and seems to be importantly involved in inflammatory processes. PAR2 can be activated by serine proteases such as trypsin, mast cell tryptase, and bacterial proteases, such as gingipain produced by Porphyromonas gingivalis. This review describes the current stage of knowledge of the possible mechanisms that link PAR2 activation with periodontal disease, and proposes future therapeutic strategies to modulate the host response in the treatment of periodontitis.

Proteinase-activated receptor-2 (PAR2) agonist causes periodontitis in rats

Proteinase-activated receptor-2 (PAR2) is a G-protein-coupled receptor that mediates cellular responses to extracellular proteinases. Since PAR2 is expressed by oral epithelial cells, osteoblasts, and gingival fibroblasts, where its activation releases interleukin-8, we hypothesized that PAR2 activation may participate in periodontal disease in vivo. We investigated the role of PAR2 activation in periodontal disease in rats. Radiographic and enzymatic (myeloperoxidase) analysis revealed that topical application of PAR2 agonist causes periodontitis but also exacerbates existing periodontitis, leading to significant alveolar bone loss and gingival granulocyte infiltration. Inhibition of matrix metalloproteinase (MMP) and cyclo-oxygenase (COX) decreased PAR2 agonist-induced periodontitis. More specifically, the overexpression of COX-1, COX-2, MMP-2, and MMP-9 in gingival tissues suggests that they are involved in PAR 2-induced periodontitis. In conclusion, PAR2 agonist causes periodontitis in rats through a mechanism involving prostaglandin release and MMP activation. Inhibition of PAR2 may represent a novel approach to modulate host response in periodontitis.

Exercise training decreases mitogen-activated protein kinase phosphatase-3 expression and suppresses hepatic gluconeogenesis in obese mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Down-regulation of protease activated receptor 2, interleukin-17 and other pro-inflammatory genes by subantimicrobial doxycycline dose in a rat periodontitis model

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Lufaxin, a Novel Factor Xa Inhibitor From the Salivary Gland of the Sand Fly Lutzomyia longipalpis Blocks Protease-Activated Receptor 2 Activation and Inhibits Inflammation and Thrombosis In Vivo

Objective-Blood-sucking arthropods' salivary glands contain a remarkable diversity of antihemostatics. The aim of the present study was to identify the unique salivary anticoagulant of the sand fly Lutzomyia longipalpis, which remained elusive for decades. Methods and Results-Several L. longipalpis salivary proteins were expressed in human embryonic kidney 293 cells and screened for inhibition of blood coagulation. A novel 32.4-kDa molecule, named Lufaxin, was identified as a slow, tight, noncompetitive, and reversible inhibitor of factor Xa (FXa). Notably, Lufaxin's primary sequence does not share similarity to any physiological or salivary inhibitors of coagulation reported to date. Lufaxin is specific for FXa and does not interact with FX, Dansyl-Glu-Gly-Arg-FXa, or 15 other enzymes. In addition, Lufaxin blocks prothrombinase and increases both prothrombin time and activated partial thromboplastin time. Surface plasmon resonance experiments revealed that FXa binds Lufaxin with an equilibrium constant approximate to 3 nM, and isothermal titration calorimetry determined a stoichiometry of 1:1. Lufaxin also prevents protease-activated receptor 2 activation by FXa in the MDA-MB-231 cell line and abrogates edema formation triggered by injection of FXa in the paw of mice. Moreover, Lufaxin prevents FeCl3-induced carotid artery thrombus formation and prolongs activated partial thromboplastin time ex vivo, implying that it works as an anticoagulant in vivo. Finally, salivary gland of sand flies was found to inhibit FXa and to interact with the enzyme. Conclusion-Lufaxin belongs to a novel family of slow-tight FXa inhibitors, which display antithrombotic and anti-inflammatory activities. It is a useful tool to understand FXa structural features and its role in prohemostatic and proinflammatory events. (Arterioscler Thromb Vasc Biol. 2012;32:2185-2196.)

Tauroursodeoxycholic Acid Affects PPAR gamma and TLR4 in Steatotic Liver Transplantation

Numerous steatotic livers are discarded for transplantation because of their poor tolerance to ischemia-reperfusion (I/R). We examined whether tauroursodeoxycholic acid (TUDCA), a known inhibitor of endoplasmic reticulum (ER) stress, protects steatotic and nonsteatotic liver grafts preserved during 6 h in University of Wisconsin (UW) solution and transplanted. The protective mechanisms of TUDCA were also examined. Neither unfolded protein response (UPR) induction nor ER stress was evidenced in steatotic and nonsteatotic liver grafts after 6 h in UW preservation solution. TUDCA only protected steatotic livers grafts and did so through a mechanism independent of ER stress. It reduced proliferator-activated receptor-gamma(PPAR gamma) and damage. When PPAR gamma was activated, TUDCA did not reduce damage. TUDCA, which inhibited PPAR gamma, and the PPAR gamma antagonist treatment up-regulated toll-like receptor 4 (TLR4), specifically the TIR domain-containing adaptor inducing IFN beta (TRIF) pathway. TLR4 agonist treatment reduced damage in steatotic liver grafts. When TLR4 action was inhibited, PPAR gamma antagonists did not protect steatotic liver grafts. In conclusion, TUDCA reduced PPAR gamma and this in turn up-regulated the TLR4 pathway, thus protecting steatotic liver grafts. TLR4 activating-based strategies could reduce the inherent risk of steatotic liver failure after transplantation.

Human beta-defensin 2 and protease activated receptor-2 expression in patients with chronic periodontitis

Objective: Some previous studies have shown that gingipains, trypsin-like proteases produced by Porphyromonas gingivalis, up-regulate human beta defensin-2 (HBD-2) mRNA expression through protease-activated receptor-2 (PAR(2)) in gingival epithelial cells. This study aimed at investigating salivary HBD-2 levels and crevicular PAR(2) mRNA expression in human chronic periodontitis and evaluating whether periodontal treatment affected this process. Methods: Salivary and gingival crevicular fluid (GCF) samples were collected from periodontally healthy (control) and chronic periodontitis patients at baseline and 50 days after nonsurgical periodontal treatment. Salivary HBD-2, and GCF TNF-alpha levels were analysed by ELISA, and PAR(2) mRNA at the GCF was evaluated by RT-PCR. Results: P. gingivalis was significantly (p < 0.05) more prevalent in patients with chronic periodontitis when compared to controls. This prevalence decreased after periodontal therapy (p < 0.0001). The control group showed statistically significant lower levels of HBD-2, TNF-alpha, and PAR(2) expression when compared to the chronic periodontitis group. In addition, periodontal treatment significantly reduced PAR(2) expression and HBD-2 levels in chronic periodontitis patients (p < 0.001). Conclusions: Our results suggest that salivary HBD-2 levels and PAR(2) mRNA expression from GCF are higher in subjects with chronic periodontitis than in healthy subjects, and that periodontal treatment decreases both HBD-2 levels and PAR(2) expression. (C) 2012 Elsevier Ltd. All rights reserved.

PPAR-gamma agonists, mainly 15d-PGJ(2), reduce eosinophil recruitment following allergen challenge

We evaluate the immunomodulation of Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists 15d-PGJ(2) and rosiglitazone (RGZ) in a model of chronic eosinophilia. 15d-PGJ(2) and RGZ significantly reduce eosinophil migration into the peritoneal cavity and down-regulate the eosinopoiesis. The synthesis of IL-5 was decreased after the treatment with 15d-PGJ(2) and RGZ corroborating with the eosinophil migration inhibition. However, IgE was decreased only after the administration of 15d-PGJ(2) in part due to B-cell inhibition. We also observed a decrease in the synthesis of IL-33, IL-17 and IL-23, suggesting that besides the modulation of Th2 pattern, there is a modulation via IL-23 and IL-17 suggesting a role of these cytokines in the eosinophil recruitment. In fact IL-17(-1-) mice failed to develop an eosinophilic response. Altogether, the results showed that PPAR-gamma agonists mainly 15d-PGJ(2), have therapeutic efficacy in eosinophil-induced diseases with an alternative mechanism of control, via IL-23/IL-17 and IL-33. (C) 2011 Elsevier Inc. All rights reserved.

Periodontal treatment downregulates protease-activated receptor 2 in human gingival crevicular fluid cells

Protease-activated receptor 2 (PAR2) is implicated in the pathogenesis of chronic inflammatory diseases, including periodontitis; it can be activated by gingipain and produced by Porphyromonas gingivalis and by neutrophil protease 3 (P3). PAR2 activation plays a relevant role in inflammatory processes by inducing the release of important inflammatory mediators associated with periodontal breakdown. The effects of periodontal treatment on PAR2 expression and its association with levels of proinflammatory mediators and activating proteases were investigated in chronic periodontitis patients. Positive staining for PAR2 was observed in gingival crevicular fluid cells and was reflective of tissue destruction. Overexpression of PAR2 was positively associated with inflammatory clinical parameters and with the levels of interleukin-6 (IL-6), IL-8, tumor necrosis factor alpha, matrix metalloprotease 2 (MMP-2), MMP-8, hepatocyte growth factor, and vascular endothelial growth factor. Elevated levels of gingipain and P3 and decreased levels of dentilisin and the protease inhibitors secretory leukocyte protease inhibitor and elafin were also associated with PAR2 overexpression. Healthy periodontal sites from individuals with chronic periodontitis showed diminished expression of PAR2 mRNA and the PAR2 protein (P < 0.05). Furthermore, periodontal treatment resulted in decreased PAR2 expression and correlated with decreased expression of inflammatory mediators and activating proteases. We concluded that periodontal treatment resulted in decreased levels of proteases and that proinflammatory mediators are associated with decreased PAR2 expression, suggesting that PAR2 expression is influenced by the presence of periodontal infection and is not a constitutive characteristic favoring periodontal inflammation.