Peptide Hp(2-20) accelerates healing of TNBS-induced colitis in the rat.

BACKGROUND AND AIMS: Hp(2-20), a Helicobacter pylori-derived peptide interacting with N-formyl peptide receptors (FPRs), accelerates the healing of gastric injury in rats. Whether Hp(2-20) affects the recovery of inflamed colonic mucosa is unknown. We evaluated whether Hp(2-20) accelerated the healing of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis and explored the mechanism(s) underlying any such effect. METHODS: Fifteen rats underwent rectal administration of Hp(2-20) 250-500 µg/kg/day, or of its control peptide Hp1 for 10 days, following induction of colitis with TNBS. Macroscopic and histological damage was quantified using predetermined injury scores. FPR1, COX-2, TNF-α, TGF-ß, HB-EGF and tissue transglutaminase (t-TG) messenger RNA (mRNA) expression in colonic tissue was determined by quantitative polymerase chain reaction; FPR1, TNF-α and COX-2 protein levels by Western blotting. RESULTS: (1) Hp(2-20) accelerated healing of TNBS-induced colitis compared to controls consistently with the expression of FPRs in colonic mucosa; (2) TNBS upregulated mRNA mucosal expression of COX-2, TNF-α, TGF-ß, HB-EGF and t-TG and (3) this, with the exception of HB-EGF, was significantly counteracted by Hp(2-20). CONCLUSIONS: Hp(2-20), an FPR agonist, accelerates the healing of TNBS-induced colitis in the rat. This effect is associated with a significant reduction in colonic tissue levels of COX-2, TGF-ß, TNF-α and t-TG. We postulate that FPR-dependent pathways may be involved in the repair of inflamed colonic mucosa.

Role of Formyl Peptide Receptors in Gastrointestinal Healing.

The wound healing and the barrier restoration of the gastrointestinal (GI) mucosa must be continuously ensured to allow homeostasis of the gastrointestinal tract and of all the surrounding tissues. Several lines of the evidence report a key role of innate immunity, and in particular of Pattern Recognition Receptors (PRRs), in controlling the homeostasis of GI tract by sensing commensal and pathogen bacteria, activating the immune response and regulating epithelial repair, thus guaranteeing the morphological and functional recovery of the injured tissue. We will discuss the role of a particular class of PRRs - the Formyl Peptide Receptors - in the homeostasis of GI mucosa. We here report the results of studies that strongly suggest the possibility that the activation of FPRs is crucial in the maintenance of homeostasis of the GI tract and provide indications of the potential clinical relevance of new treatment regimens involving FPR modulation for several GI disorders.

Mast cells induce epithelial-to-mesenchymal transition and stem cell features in human thyroid cancer cells through an IL-8-Akt-Slug pathway.

There is increasing evidence that mast cells (MCs) and their mediators are involved in the remodeling of the tumor microenvironment and promote tumor growth, angiogenesis and metastasis. We have found that an increased density of MCs in thyroid cancer (TC) correlates with enhanced invasiveness. However, the MC-derived factors responsible for this activity and the mechanisms by which they enhance TC invasiveness remain unidentified. Here, we report that MCs, when activated by TC cells, produce soluble factors that induce epithelial-to-mesenchymal transition (EMT) and stemness features of TC cells. We identified CXCL8/interleukin (IL)-8 as the main mediator contained in activated MC conditioned media (CM) capable of inducing both EMT and stemness of TC cells. Mechanistically, MC CM or exogenous IL-8 stimulated Akt phosphorylation and Slug expression in TC cells. The inhibition of the Akt pathway or depletion of the Slug transcription factor by RNA interference, reverted EMT and stemness responses. TC cells stably transfected with exogenous IL-8 underwent EMT, displayed increased stemness and enhanced tumorigenicity with respect to control cells. The analysis of TC surgical specimens by immunohistochemical analysis demonstrated a positive correlation between MC density (Tryptase(+) cells) and stemness features (OCT4 staining). Taken together, our data identify an MC-dependent IL-8-Akt-Slug pathway that sustains EMT/stemness of TC cells. The blockade of this circuit might be exploited for the therapy of advanced TC.

The formyl peptide receptor 1 exerts a tumor suppressor function in human gastric cancer by inhibiting angiogenesis.

N-formyl peptide receptors (FPR1, FPR2 and FPR3) are involved in innate immunity, inflammation and cancer. FPR expression, initially described in immune cells, was later observed in non-hematopoietic cell populations and tissues. Several studies suggested a role for FPRs in the progression of various tumor histotypes, including gastric cancer (GC), for which a positive association with a specific FPR1 polymorphism has recently been described. We previously showed that FPRs are expressed on gastric epithelium and are required for wound repair and restitution of barrier integrity. Here we assess the role of FPRs in GC. We characterized the functions of FPRs in GC epithelial cells (MKN28, AGS and MKN45) cultured in vitro by assessing migration, proliferation, resistance to apoptosis and activation of the epithelial-to-mesenchymal transition. Activation of each FPR induced the epithelial-to-mesenchymal transition, proliferation, resistance to apoptosis and migration of GC cells in culture. Blocking compounds or RNA interference of each FPR reverted these effects. We also defined the in vivo tumorigenic potential of GC epithelial cells silenced for FPRs by xenograft experiments in immunocompromised mice. Interestingly, FPR1 silencing in GC cells (shFPR1) significantly enhanced xenograft growth with respect to shCTR, shFPR2 and shFPR3 xenografts, because of augmented vessel density and cell proliferation. Accordingly, HIF-1α and VEGF mRNA levels were higher in shFPR1 xenografts than in controls. Moreover, the in vitro production of proangiogenic factors in response to FPR2/3 agonists (WKYMVm, LL-37, uPA, uPAR84-95, AnxA1) or to other proinflammatory mediators (IL-1α) was higher in shFPR1 GC cells than in shCTR, shFPR2 and shFPR3 cells, suggesting that FPR1 functions as an inhibitor of CG angiogenesis. Thus, we propose that FPR1 stimulation may represent a novel therapeutic approach to counteract tumor angiogenesis.

Expression and function of Angiopoietins and their tie receptors in human basophils and mast cells.

The Angiopoietin/Tie system is a key regulator of vascular remodeling, maturation, angiogenesis and lymphangiogenesis. In humans there are three angiopoietins: Angiopoietin-1 (Ang1), Angiopoietin-2 (Ang2), and Angiopoietin-4 (Ang4). Ang1 and Ang2 are the best characterized angiopoietins. The angiopoietin receptor system consists of two type I tyrosine kinase receptors (Tie1 and Tie2). Tie2 binds all known angiopoietins. We sought to characterize Ang1, Ang2, Tie1 and Tie2 expression and functions in human basophils and mast cells. Basophils, LAD-2 cells and Human Lung Mast Cells (HLMCs) constitutively express Ang1 and Ang2 mRNA. Intracellular staining for Ang1 and Ang2 was stronger in basophils than in mast cells. Immunoelectron microscopy demonstrated Ang1 in cytoplasmic vesicles of basophils. The protein kinase C activators phorbol diester (PMA) and bryostatin 1 (Bryo1) stimulated basophils to rapidly release a large amount of Ang1. PMA-induced Ang1 release was inhibited by brefeldin A. Tie1 and Tie2 mRNAs were expressed in basophils, LAD-2 and HLMCs. Basophils, LAD-2 and HLMCs expressed Tie1 on the cell surface. HLMCs and LAD-2 expressed Tie2 on the cell surface, whereas basophils did not. Ang1, but not Ang2, induced migration of mast cells through the engagement of Tie2. Neither Ang1 nor Ang2 induced basophil chemotaxis. We have identified a novel mechanism of cross-talk between human basophils and mast cells mediated by the Ang1/Tie2 system that might be relevant in the orchestration of inflammatory and neoplastic angiogenesis.

Helicobacter pylori HP(2-20) induces eosinophil activation and accumulation in superficial gastric mucosa and stimulates VEGF-alpha and TGF-beta release by interacting with formyl-peptide receptors.

Eosinophils participate in the immune response against Helicobacter pylori, but little is known about their role in the gastritis associated to the infection. We recently demonstrated that the Hp(2-20) peptide derived from H. pylori accelerates wound healing of gastric mucosa by interacting with N-formyl peptide receptors (FPRs) expressed on gastric epithelial cells. The aim of the present study was to investigate whether eosinophils play a role in the repair of gastric mucosa tissue during H. pylori infection. Immuno-histochemistry and transmission electron microscopy were used to detect eosinophils in gastric mucosal biopsies. Eosinophil re-distribution occurred in the gastric mucosa of H. pylori-infected patients: their density did not change in the deep mucosal layer, whereas it increased in the superficial lamina propria just below the foveolar epithelium; eosinophils entered the epithelium itself as well as the lumen of foveolae located close to the area harboring bacteria, which in turn were also engulfed by eosinophils. The H. pylori-derived peptide Hp(2-20) stimulated eosinophil migration through the engagement of FPR2 and FPR3, and also induced production of VEGF-A and TGF-beta, two key mediators of tissue remodelling. We also demonstrate that Hp(2-20) in vivo induced eosinophil infiltration in rat gastric mucosa after injury brought about by indomethacin. This study suggests that eosinophil infiltrate could modulate the capacity of gastric mucosa to maintain or recover its integrity thereby shedding light on the role of eosinophils in H. pylori infection.

Hp(2-20) peptide of Helicobacter pylori and the innate immune receptors: specific role(s) of the formyl peptide receptors.

Helicobacter pylori (H. pylori) is a microaerophilic, Gram-negative bacterium that affects more than half of the world's population. H. pylori has co-evolved with humans to be transmitted from person to person and to persistently colonize the stomach. A well-choreographed equilibrium between bacterial effectors and host responses permits microbial persistence and health of the host but confers risk of serious diseases. During its long coexistence with humans, H. pylori has evolved complex strategies to limit the degree and extent of gastric mucosal damage and inflammation as well as immune effector activity. In this complex strategy an important role is played by the interaction of H. pylori with a specific class of innate immune receptors, named N-formyl peptide receptor family (FPRs). In the last years several virulence factors have been studied in an effort to correlate bacterial phenotype with specific gastric manifestations and to clarify the pathogenetic mechanisms. Several peptides produced by H. pylori appear to be involved in inflammation associated with the infection. A particular interest has been focused on the Hp(2-20) peptide derived from the bacteria. Thus, aim of the article is to comment on some advances in the elucidation of specific interactions between the Hp(2-20) peptide and FPRs.

Role(s) of formyl-peptide receptors expressed in nasal epithelial cells.

Chronic rhinosinusitis is one of the most frequent chronic diseases in humans. Little is known about stimuli initiating tissue remodeling process that determines the morphological expression of the disease. N-formyl peptide receptors (FPRs) are innate immunity receptors important in tissue remodeling of gastric and intestinal epithelium. The expression and functions of FPRs in nasal epithelial cells were examined to evaluate whether they could be important in the remodeling of nasal mucosa. The aim of this study is to examine FPR expression in a nasal epithelial cell line (RPMI-2650) at mRNA and protein levels. To determine whether FPRs were functional, chemotaxis experiments were carried out. In addition the effects of FPRs agonists on the expression (PCR and ELISA) of VEGF-A and TGF-beta, two key mediators of tissue remodelling, were examined. Here we demonstrate that RPMI-2650 express FPR and FPRL2, but not FPRL1. fMLP, a bacterial product active on FPR, and uPAR(84-95), an inflammatory mediator agonist for FPRL2, stimulated migration of nasal epithelial cells. fMLP and uPAR(84-95) induce expression and secretion of VEGF-A and TGF-beta. Our results suggest a possible mechanisms initiating tissue remodeling observed during chronic rhinosinusitis. This study provides further evidence that FPRs play a more complex role in human pathophysiology than bacterial recognition.

Mast cells have a protumorigenic role in human thyroid cancer.

In different human carcinoma types, mast cell infiltrate increases with respect to normal tissue and mast cell density correlates with a bad prognosis. To assess the role of mast cells in human thyroid cancer, we compared the density of tryptase-positive mast cells in 96 papillary thyroid carcinomas (PTCs) versus normal thyroid tissue from 14 healthy individuals. Mast cell density was higher in 95% of PTCs (n=91) than in control tissue. Mast cell infiltrate correlated with extrathyroidal extension (P=0.0005) of PTCs. We show that thyroid cancer cell-line-derived soluble factors induce mast cell activation and chemoattraction in vitro. Different mast cell lines (HMC-1 and LAD2) and primary human lung mast cells induced thyroid cancer cell invasive ability, survival and DNA synthesis in vitro. The latter effect was mainly mediated by three mast-cell-derived mediators: histamine, and chemokines CXCL1/GROα and CXCL10/IP10. We show that xenografts of thyroid carcinoma cells (8505-C) could recruit mast cells injected into the tail vein of mice. Co-injection of human mast cells accelerated the growth of thyroid cancer cell (8505-C) xenografts in athymic mice. This effect was mediated by increased tumor vascularization and proliferation, and was reverted by treating mice with sodium cromoglycate (Cromolyn), a specific mast cell inhibitor. In conclusion, our study data suggest that mast cells are recruited into thyroid carcinomas and promote proliferation, survival and invasive ability of cancer cells, thereby contributing to thyroid carcinoma growth and invasiveness.

Human urotensin II induces tissue factor and cellular adhesion molecules expression in human coronary endothelial cells: an emerging role for urotensin II in cardiovascular disease.

BACKGROUND: Human urotensin II is an 11-aminoacid peptide with a controversial role in the human cardiovascular system. Indeed, urotensin effects on vascular reactivity and in heart failure are well documented, while its potential role in the pathophysiology of athero-thrombosis is still unknown. This study investigates the effects of urotensin on tissue factor (TF) and VCAM-1/ICAM-1 expression in human coronary endothelial cells (HCAECs). METHODS AND RESULTS: Urotensin induced TF-mRNA transcription as demonstrated by real time PCR and expression of TF that was functionally active as demonstrated by procoagulant activity assay. In addition, urotensin induced expression of VCAM-1 and ICAM-1 as demonstrated by FACS analysis. VCAM-1 and ICAM-1 were functionally active because they increased leukocyte adhesivity to HCAECs. Urotensin-induced expression of TF and of VCAM-1/ICAM-1 was mediated through the Rho A-activation of the transcription factor, NF-kappaB, as demonstrated by EMSA. Indeed, lovastatin, an HMG-CoA reductase inhibitor, by modulating the Rho activation, and NF-kappaB inhibitors, suppressed the urotensin effects on TF and CAMs. CONCLUSIONS: Data of the present study, although in vitro, describe the close relationship existing between urotensin II and athero-thrombosis, providing for the first time support for the view that this peptide might have not only vasoactive functions but it might be an effector molecule able to induce a pro-atherothrombotic phenotype in cells of the coronary circulation. Although future studies are required to clarify whether these mechanisms are also important in the clinical setting, this report supports an emerging new role for urotensin II in the pathogenesis and progression of cardiovascular disease.

Neopterin induces pro-atherothrombotic phenotype in human coronary endothelial cells.

BACKGROUND: Inflammation plays a pivotal role in atherothrombosis. Recent data indicate that serum levels of neopterin, a marker of inflammation and immune modulator secreted by monocytes/macrophages, are elevated in patients with acute coronary syndromes and seem to be a prognostic marker for major cardiovascular events. The aim of the present study was to determine whether neopterin might affect the thrombotic and atherosclerotic characteristics of human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: In HCAECs, neopterin induced TF-mRNA transcription as demonstrated by real time polymerase chain reaction and expression of functionally active tissue factor (TF) as demonstrated by procoagulant activity assay, and of cellular adhesion molecules (CAMs) as demonstrated by FACS analysis, in a dose-dependent fashion. These neopterin effects were prevented by lovastatin, a HMG-CoA reductase inhibitor. Neopterin-induced TF and CAMs expression was mediated by oxygen free radicals through the activation of the transcription factor, nuclear factor-kappa B (NF-kappaB), as demonstrated by electrophoretic mobility shift assay and by suppression of CAMs and TF expression by superoxide dismutase and by NF-kappaB inhibitor, pyrrolidine-dithio-carbamate ammonium. CONCLUSIONS: These data indicate that neopterin exerts direct effects on HCAECs by promoting CAMs and TF expression and support the hypothesis that neopterin, besides representing a marker of inflammation, might be an effector molecule able to induce a pro-atherothrombotic phenotype in cells of the coronary circulation.

Tat protein is an HIV-1-encoded beta-chemokine homolog that promotes migration and up-regulates CCR3 expression on human Fc epsilon RI+ cells.

Human basophils and mast cells express the chemokine receptor CCR3, which binds the chemokines eotaxin and RANTES. HIV-1 Tat protein is a potent chemoattractant for basophils and lung mast cells obtained from healthy individuals seronegative for Abs to HIV-1 and HIV-2. Tat protein induced a rapid and transient Ca(2+) influx in basophils and mast cells, analogous to beta-chemokines. Tat protein neither induced histamine release from human basophils and mast cells nor increased IL-3-stimulated histamine secretion from basophils. The chemotactic activity of Tat protein was blocked by preincubation of FcepsilonRI(+) cells with anti-CCR3 Ab. Preincubation of Tat with a mAb anti-Tat (aa 1-86) blocked the migration induced by Tat. In contrast, a mAb specific for the basic region (aa 46-60) did not inhibit the chemotactic effect of Tat protein. Tat protein or eotaxin desensitized basophils to a subsequent challenge with the autologous or the heterologous stimulus. Preincubation of basophils with Tat protein up-regulated the level of CCR3 mRNA and the surface expression of the CCR3 receptor. Tat protein is the first identified HIV-1-encoded beta-chemokine homologue that influences the directional migration of human FcepsilonRI(+) cells and the expression of surface receptor CCR3 on these cells.