Therapeutic options in inflammatory bowel disease: experimental evidence of a beneficial effect of kinin B1 receptor blockade.

A surprising proportion of patients with inflammatory bowel disease (IBD) remain refractory to all classes of drugs presently in clinical use. Kinins are inflammatory mediators of potential relevance in IBD, because at least the kinin B1 receptor subtype is upregulated in human or animal intestinal inflammation and also both B1 and B2 receptors for kinins support inflammation and epithelial electrogenic ion transport that leads to secretory diarrhoea. In this issue of the BJP, Hara et al.

Nucleobindin co-localizes and associates with cyclooxygenase (COX)-2 in human neutrophils.

The inducible cyclooxygenase isoform (COX-2) is associated with inflammation, tumorigenesis, as well as with physiological events. Despite efforts deployed in order to understand the biology of this multi-faceted enzyme, much remains to be understood. Nucleobindin (Nuc), a ubiquitous Ca(2+)-binding protein, possesses a putative COX-binding domain.

Alpha1beta1 integrin and interleukin-7 receptor up-regulate the expression of RANKL in human T cells and enhance their osteoclastogenic function.

Activated T cells, through the production of the receptor activator of NF-kappaB ligand (RANKL) cytokine, have been implicated in the osteoclast development and bone loss that are associated with autoimmune diseases such as rheumatoid arthritis. However, the cellular pathways that regulate the expression of RANKL and the induction of osteoclasts are still unclear. In this study, we show that, in human effector CD4(+) T cells, activation of alpha1beta1 integrin and interleukin (IL)-7 receptor (IL-7R) up-regulates the expression and production of RANKL but has no effect on the production of interferon-gamma, an inhibitor of T-cell-mediated osteoclastogenesis.

Munc13-4 regulates granule secretion in human neutrophils.

The neutrophil plays a central role in the innate host immune defense. Regulated exocytosis of its granules and release of antimicrobial and cytotoxic substances are key events to limit the spread of pathogens. However, the molecular mechanisms that control exocytosis of neutrophil granules are ill-defined.

Comparative hydrolysis of P2 receptor agonists by NTPDases 1, 2, 3 and 8.

Nucleoside triphosphate diphosphohydrolases 1, 2, 3 and 8 (NTPDases 1, 2, 3 and 8) are the dominant ectonucleotidases and thereby expected to play important roles in nucleotide signaling. Distinct biochemical characteristics of individual NTPDases should allow them to regulate P2 receptor activation differentially. Therefore, the biochemical and kinetic properties of these enzymes were compared.

Receptor-independent, vacuolar ATPase-mediated cellular uptake of histamine receptor-1 ligands: possible origin of pharmacological distortions and side effects.

The aims of this study were to investigate whether several histamine receptor agonists and antagonists are subjected to receptor-independent ion trapping into acidic organelles, and whether this sequestration influences their pharmacological or toxicological properties. Vacuolar (V)-ATPase-dependent intracellular sequestration of agonists was recognized as morphological alterations (large fluid-filled vacuoles for betahistine and 1-methylhistamine, granular uptake for fluorescent BODIPY FL histamine) prevented by the specific V-ATPase inhibitor bafilomycin A1 in rabbit vascular smooth muscle cells. Lipophilicity was the major determinant of these cellular effects (order of potency: BODIPY FL histamine>betahistine>1-methylhistamine>histamine) that occurred at high concentrations.

Identification of functional microRNAs released through asymmetrical processing of HIV-1 TAR element.

The interaction between human immunodeficiency virus type 1 (HIV-1) and RNA silencing pathways is complex and multifaceted. Essential for efficient viral transcription and supporting Tat-mediated transactivation of viral gene expression, the trans-activation responsive (TAR) element is a structured RNA located at the 5' end of all transcripts derived from HIV-1. Here, we report that this element is a source of microRNAs (miRNAs) in cultured HIV-1-infected cell lines and in HIV-1-infected human CD4+ T lymphocytes.

Intense pseudotransport of a cationic drug mediated by vacuolar ATPase: procainamide-induced autophagic cell vacuolization.

Cationic drugs frequently exhibit large apparent volumes of distribution, consistent with various forms of cellular sequestration. The contributions of organelles and metabolic processes that may mimic drug transport were defined in human vascular smooth muscle cells. We hypothesized that procainamide-induced vacuolar cytopathology is driven by intense pseudotransport mediated by the vacuolar (V)-ATPase and pursued the characterization of vesicular trafficking alterations in this model.

Down-regulation of mcl-1 by small interfering RNA sensitizes resistant melanoma cells to fas-mediated apoptosis.

Resistance of malignant melanoma cells to Fas-mediated apoptosis is among the mechanisms by which they escape immune surveillance. However, the mechanisms contributing to their resistance are not completely understood, and it is still unclear whether antiapoptotic Bcl-2-related family proteins play a role in this resistance. In this study, we report that treatment of Fas-resistant melanoma cell lines with cycloheximide, a general inhibitor of de novo protein synthesis, sensitizes them to anti-Fas monoclonal antibody (mAb)-induced apoptosis.

Lack of direct interaction between enalaprilat and the kinin B1 receptors.

It has been recently proposed that the second extracellular loop of the human bradykinin (BK) B1 receptor (B1R) contains a conserved HExxH motif also present in peptidases possessing a Zn2+ prosthetic group, such as angiotensin converting enzyme (ACE), and that ACE inhibitors directly activate B1R signaling in endothelial cells. However, the binding of ACE inhibitors to the B1Rs has never been directly evaluated. Information about binding of a radiolabeled inhibitor to natural or recombinant ACE in intact cells (physiologic ionic composition) was also collected.

Normal human primary CD4+ T lymphocytes synthesize and release functional osteoprotegerin in vitro.

Osteoprotegerin (OPG) acts as a decoy receptor for receptor activator of nuclear factor-kappaB ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL). OPG regulates bone remodeling and the immune response. The primary objective was to decipher, among human peripheral blood mononuclear leukocytes (PBML) that produce OPG, the subset(s) responsible for this synthesis and its regulation.

Trapping of adrenergic decongestant drugs into cellular endomembrane compartments: toxicological and pharmacological consequences.

Rhinitis of allergic and viral origin is often self-treated by patients with locally applied vasoconstrictor decongestant drugs. In turn, prolonged use of these agents produce an inflammatory condition termed rhinitis medicamentosa. Cationic drugs are sequestered into cells via various mechanisms, including mitochondrial concentration and V-ATPase-driven trapping in vacuoles that swell by an osmotic mechanism.

Regulation of lysophosphatidic acid receptor expression and function in human synoviocytes: implications for rheumatoid arthritis?

Lysophosphatidic acid (LPA), via interaction with its G-protein coupled receptors, is involved in various pathological conditions. Extracellular LPA is mainly produced by the enzyme autotaxin (ATX). Using fibroblast-like synoviocytes (FLS) isolated from synovial tissues of patients with rheumatoid arthritis (RA), we studied the expression profile of LPA receptors, LPA-induced cell migration, and interleukin (IL)-8 and IL-6 production.

Involvement of Dcr1 in post-transcriptional regulation of gene expression in Schizosaccharomyces pombe.

The ribonuclease III Dicer (Dcr1) has been shown to be required for chromosome segregation and gene silencing in Schizosaccharomyces pombe. These effects are thought to be transcriptional, mediated by formation and maintenance of heterochromatin, and guided by small RNAs derived from Dcr1 along a process known as RNA interference. In order to get further insights into the gene regulatory role of Dcr1, we performed comparative analyses of dcr1 knockout and wild-type fission yeast strains.

[Neutrophils and immunity: is it innate or acquired?].

The neutrophil has long been considered a phagocytic cell with a short life-span whose major role is to destroy intruders to the body. Toll receptors and anti-infectious factors such as defensin, perforin and granzymes are newly discovered mechanisms used by neutrophils for the first line of defense against invaders. Moreover, subpopulations of neutrophils share specific functions like the synthesis of certain cytokines and chemokines, as well as the expression of immunoreceptors like the T cell receptor.

Cardiovascular expression of inflammatory signaling molecules, the kinin B1 receptor and COX2, in the rabbit: effects of LPS, anti-inflammatory and anti-hypertensive drugs.

We first aimed to test the effect of anti-inflammatory drugs, etanercept and dexamethasone sodium phosphate (DSP), on the expression of inducible inflammatory signaling molecules (the bradykinin [BK] B(1) receptor [B(1)R], cyclooxygenase [COX]-2) in lipopolysaccharide (LPS)-treated rabbits. Preliminary experiments mostly based on a novel cellular model, rabbit dermis fibroblasts, showed that etanercept inhibited TNF-alpha-induced B(1)R expression ([(3)H]Lys-des-Arg(9)-BK binding), but that DSP also inhibited cytokine-induced B(1)R upregulation with less selectivity. LPS (100 microg/kg i.

Inhibition of human and mouse plasma membrane bound NTPDases by P2 receptor antagonists.

The plasma membrane bound nucleoside triphosphate diphosphohydrolase (NTPDase)-1, 2, 3 and 8 are major ectonucleotidases that modulate P2 receptor signaling by controlling nucleotides' concentrations at the cell surface. In this report, we systematically evaluated the effect of the commonly used P2 receptor antagonists reactive blue 2, suramin, NF279, NF449 and MRS2179, on recombinant human and mouse NTPDase1, 2, 3 and 8. Enzymatic reactions were performed in a Tris/calcium buffer, commonly used to evaluate NTPDase activity, and in a more physiological Ringer modified buffer.

B-9972 (D-Arg-[Hyp3,Igl5,Oic7,Igl8]-bradykinin) is an inactivation-resistant agonist of the bradykinin B2 receptor derived from the peptide antagonist B-9430 (D-Arg-[Hyp3,Igl5,D-Igl7,Oic8]-bradykinin): pharmacologic profile and effective induction of receptor degradation.

The bradykinin B(2) receptor is a heptahelical receptor regulated by a cycle of phosphorylation, endocytosis, and extensive recycling at the cell surface following agonist stimulation. B-9430 (d-Arg-[Hyp(3),Igl(5),D-Igl(7),Oic(8)]-bradykinin) is a second generation peptide antagonist found to be competitive at the human B(2) receptor and insurmountable at the rabbit B(2) receptor (contractility assays, isolated human umbilical and rabbit jugular veins). Two isomers of this peptide were prepared: B-10344 (D-Arg-[Hyp(3),Igl(5),Oic(7),D-Igl(8)]-bradykinin; inverted sequence Oic(7), D-Igl(8)) and B-9972 (D-Arg-[Hyp(3),Igl(5),Oic(7),Igl(8)]-bradykinin); they are low- and high-potency agonists, respectively, in vascular preparations.

Characterization of prostaglandin E2 generation through the cyclooxygenase (COX)-2 pathway in human neutrophils.

In the present study, we characterized the generation of prostaglandin (PG)E2 in human neutrophils. We found that the Ca2+-dependent type IV cytosolic phospholipase A2 (cPLA2) was pivotally involved in the COX-2-mediated generation of PGE2 in response to a calcium ionophore, as determined by the use of selected PLA2 inhibitors. PGE2 biosynthesis elicited by bacterial-derived peptides or by phagocytic stimuli acting on cell surface receptors also showed to be dependent on cPLA2 activity.

Specificity of the ecto-ATPase inhibitor ARL 67156 on human and mouse ectonucleotidases.

Background And Purpose: ARL 67156, 6-N,N-Diethyl-D-beta-gamma-dibromomethylene adenosine triphosphate, originally named FPL 67156, is the only commercially available inhibitor of ecto-ATPases. Since the first report on this molecule, various ectonucleotidases responsible for the hydrolysis of ATP at the cell surface have been cloned and characterized. In this work, we identified the ectonucleotidases inhibited by ARL 67156.

[Early phase of HHV6 infection: role of IE1 and IE2 proteins].

Human herpesvirus 6 (HHV6) is an opportunistic pathogen whose infection or reactivation is associated with diseases such as roseola, central nervous system disorders and organ transplant anomalies. Following its entry into the host cell, the virus utilizes the cellular machinery in order to transcribe its genes and insure the replicative cycle progression. HHV-6 can also latently persist in its host.

Crystal-induced neutrophil activation. IX. Syk-dependent activation of class Ia phosphatidylinositol 3-kinase.

The deposition of monosodium urate (MSU) crystals in the joints of humans leads to an extremely acute, inflammatory reaction, commonly known as gout, characterized by a massive infiltration of neutrophils. Direct interactions of MSU crystals with human neutrophils and inflammatory mediators are crucial to the induction and perpetuation of gout attacks. The intracellular signaling events initiated by the physical interaction between MSU crystals and neutrophils depend on the activation of specific tyrosine kinases (Src and Syk, in particular).

Alpha2 beta1 integrin signaling augments T cell receptor-dependent production of interferon-gamma in human T cells.

The mechanisms by which beta1 integrins modulate T cell costimulation are still poorly defined. In this study, we examined the role of collagen-binding integrins alpha1 beta1 and alpha2 beta1 in the regulation of interferon-gamma (IFN-gamma). We demonstrated that ligation of alpha2 beta1 integrin with Collagen type I (Coll I) but not alpha1 beta1 integrin with Collagen IV (Coll IV) significantly augmented T cell receptor (TCR)-dependent expression and production of IFN-gamma by effector T cells.

Requirement of oxidation-dependent CD40 homodimers for CD154/CD40 bidirectional signaling.

It is well established that the CD154/CD40 interaction is required for T cell-dependent B cell differentiation and maturation. However, the early molecular and structural mechanisms that orchestrate CD154 and CD40 signaling at the T cell/APC contact site are not well understood. We demonstrated that CD40 engagement induces the formation of disulfide-linked (dl) CD40 homodimers that predominantly associate with detergent-resistant membrane microdomains.