Histamine induces ATP release from human subcutaneous fibroblasts, via pannexin-1 hemichannels, leading to Ca2+ mobilization and cell proliferation.

Changes in the regulation of connective tissue ATP-mediated mechano-transduction and remodeling may be an important link to the pathogenesis of chronic pain. It has been demonstrated that mast cell-derived histamine plays an important role in painful fibrotic diseases. Here we analyzed the involvement of ATP in the response of human subcutaneous fibroblasts to histamine.

Cross-linking of IgGs bound on circulating neutrophils leads to an activation of endothelial cells: possible role of rheumatoid factors in rheumatoid arthritis-associated vascular dysfunction.

Background: Rheumatoid arthritis is characterized by the presence of circulating auto-antibodies, including rheumatoid factors, which recognize the Fc portion of IgGs. The neutrophil is the most abundant circulating leukocyte and it expresses high levels of FcγRs on its surface. The aim of the present study was to examine the capacity of circulating human neutrophils to be activated by rheumatoid factors and the consequences of these events on endothelium.

High affinity capture and concentration of quinacrine in polymorphonuclear neutrophils via vacuolar ATPase-mediated ion trapping: comparison with other peripheral blood leukocytes and implications for the distribution of cationic drugs.

Many cationic drugs are concentrated in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping), with an ensuing vacuolar and autophagic cytopathology. In solid tissues, there is evidence that phagocytic cells, e.g.

Inhibitory effects of cytoskeleton disrupting drugs and GDP-locked Rab mutants on bradykinin B₂ receptor cycling.

The bradykinin (BK) B₂ receptor (B₂R) is G protein coupled and phosphorylated upon agonist stimulation; its endocytosis and recycling are documented. We assessed the effect of drugs that affect the cytoskeleton on B2R cycling. These drugs were targeted to tubulin (paclitaxel, or the novel combretastatin A-4 mimetic 3,4,5-trimethoxyphenyl-4-(2-oxoimidazolidin-1-yl)benzenesulfonate [IMZ-602]) and actin (cytochalasin D).

8-BuS-ATP derivatives as specific NTPDase1 inhibitors.

Background And Purpose: Ectonucleotidases control extracellular nucleotide levels and consequently, their (patho)physiological responses. Among these enzymes, nucleoside triphosphate diphosphohydrolase-1 (NTPDase1), -2, -3 and -8 are the major ectonucleotidases responsible for nucleotide hydrolysis at the cell surface under physiological conditions, and NTPDase1 is predominantly located at the surface of vascular endothelial cells and leukocytes. Efficacious inhibitors of NTPDase1 are required to modulate responses induced by nucleotides in a number of pathological situations such as thrombosis, inflammation and cancer.

The exposure of autoantigens by microparticles underlies the formation of potent inflammatory components: the microparticle-associated immune complexes.

Immunoglobulins, antigens and complement can assemble to form immune complexes (IC). ICs can be detrimental as they propagate inflammation in autoimmune diseases. Like ICs, submicron extracellular vesicles termed microparticles (MP) are present in the synovial fluid from patients affected with autoimmune arthritis.

Platelets: active players in the pathogenesis of arthritis and SLE.

Nearly one trillion platelets circulate in the blood to monitor and preserve the integrity of the vasculature. However, haemostasis is not their only function. Platelets are also potent immune cells capable of a range of effector responses.

Platelets can enhance vascular permeability.

Platelets survey blood vessels, searching for endothelial damage and preventing loss of vascular integrity. However, there are circumstances where vascular permeability increases, suggesting that platelets sometimes fail to fulfill their expected function. Human inflammatory arthritis is associated with tissue edema attributed to enhanced permeability of the synovial microvasculature.

Cation trapping by cellular acidic compartments: beyond the concept of lysosomotropic drugs.

"Lysosomotropic" cationic drugs are known to concentrate in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping); they draw water by an osmotic mechanism, leading to a vacuolar response. Several aspects of this phenomenon were recently reexamined. (1) The proton pump vacuolar (V)-ATPase is the driving force of cationic drug uptake and ensuing vacuolization.

Coexpression of ecto-5'-nucleotidase/CD73 with specific NTPDases differentially regulates adenosine formation in the rat liver.

Ectonucleotidases modulate purinergic signaling by hydrolyzing ATP to adenosine. Here we characterized the impact of the cellular distribution of hepatic ectonucleotidases, namely nucleoside triphosphate diphosphohydrolase (NTPDase)1/CD39, NTPDase2/CD39L1, NTPDase8, and ecto-5'-nucleotidase/CD73, and of their specific biochemical properties, on the levels of P1 and P2 receptor agonists, with an emphasis on adenosine-producing CD73. Immunostaining and enzyme histochemistry showed that the distribution of CD73 (protein and AMPase activity) overlaps partially with those of NTPDase1, -2, and -8 (protein levels and ATPase and ADPase activities) in normal rat liver.

[Human herpesviruses HHV-6 and chromosomal integration: pathological and medical associated consequences].

Herpesviruses are extremely well adapted to their hosts and cause persistent infections that span over decades. Typically, these viruses establish latency by maintaining their viral genomes as extrachromosomal episomes and restricting their gene expression to a minimum. Human herpesvirus 6 (HHV-6) is perhaps one of the most well-adapted human herpesvirus with a prevalence approaching 100%.

Prolonged signalling and trafficking of the bradykinin B2 receptor stimulated with the amphibian peptide maximakinin: insight into the endosomal inactivation of kinins.

Maximakinin, a 19-residue peptide from the amphibian Bombina maxima, incorporates the full sequence of bradykinin (BK) at its C-terminus with a hydrophilic 10-residue N-terminal extension. As a putative venom component, it may stimulate BK B(2) receptors (B(2)Rs) in a distinct manner relative to the fragile mammalian agonist BK. Maximakinin affinity for B(2)Rs and angiotensin converting enzyme (ACE) and its pharmacological profile have been compared to those of BK.

An in vitro reconstitution system to address the mechanism of the vascular expression of the bradykinin B₁ receptor in response to angiotensin converting enzyme inhibition.

The expression of the bradykinin (BK) B₁ receptor (B₁R), lacking in normal vascular tissues, is induced following innate immune system activation and chronic blockade of angiotensin converting enzyme (ACE). To identify cytokine-dependent or -independent mechanisms for the latter phenomenon, the ACE inhibitor enalaprilat and several peptides potentiated in vivo by ACE blockade were applied either directly to human umbilical artery smooth muscle cells (hUA-SMCs) or to differentiated monoblastoid U937 cells to produce a conditioned medium (CM) that was later transferred to hUA-SMCs. A phagocyte stimulant, lipopolysaccharide, did not upregulate B₁R, measured using [³H]Lys-des-Arg⁹-BK binding, or translocate NF-κB to the nuclei if applied directly to the hUA-SMCs.

Oncostatin M decreases interleukin-1 β secretion by human synovial fibroblasts and attenuates an acute inflammatory reaction in vivo.

Oncostatin M (OSM) is a pleiotropic cytokine of the IL-6 family and displays both pro-inflammatory and anti-inflammatory activities. We studied the impact of OSM on the gene activation profile of human synovial cells, which play a central role in the progression of inflammatory responses in joints. In synovial cells stimulated with lipopolysaccharide and recombinant human granulocyte-macrophage colony-stimulating factor, recombinant human OSM and native OSM secreted by human granulocytes both reduced the gene expression and secretion of IL-1β and CXCL8, but increased that of IL-6 and CCL2.

Dissociation of the vacuolar and macroautophagic cytopathology from the cytotoxicity induced by the lipophilic local anesthetic bupivacaine.

Local anesthetics, like many other cationic drugs, induce a vacuolar and macroautophagic cytopathology that has been observed in vivo and in various cell types; some also induce cytotoxicity of mitochondrial origin (apoptosis and necrosis) and it is not known whether the 2 types of toxicity overlap or interact. We compared bupivacaine with a more hydrophilic agent, lidocaine, for morphological, functional, and toxicological responses in a previously exploited nonneuronal system, primary smooth muscle cells. Bupivacaine induced little vacuolization (≥2.

Bradykinin B₂ receptor-mediated transport into intact cells: anti-receptor antibody-based cargoes.

Endocytosis of the bradykinin-stimulated B(2) receptors is parallel to the transport and subsequent degradation of the ligand. To implement biotechnological applications based on receptor-mediated transport, one strategy is to conjugate the agonist ligand to a cargo. Alternatively, we studied whether the B(2) receptor can transport large antibody-based cargoes into intact cells and characterized the ensuing endosomal routing.

NTPDase1 controls IL-8 production by human neutrophils.

The ectonucleotidase NTPDase1 (CD39) terminates P2 receptor activation by the hydrolysis of extracellular nucleotides (i.e., the P2 receptor ligands).

Impact of ectoenzymes on p2 and p1 receptor signaling.

P2 receptors that are activated by extracellular nucleotides (e.g., ATP, ADP, UTP, UDP, Ap(n)A) and P1 receptors activated by adenosine control a diversity of biological processes.

Cytohesin-1 regulates human blood neutrophil adhesion to endothelial cells through β2 integrin activation.

Cytohesin-1 is a guanine nucleotide exchange factor for ADP ribosylation factor 6 (Arf6) in human blood neutrophils and differentiated PLB-985 neutrophil-like cells. Cytohesin-1 regulates adhesion and the transendothelial migration of monocytes, dendritic cells and T lymphocytes through activation of the β2 integrin LFA-1. In this study we investigated the role of cytohesin-1 in neutrophil and neutrophil-like cell adhesion to HUVECs, immobilized ICAM-1, and the α4β1 and α5β1 integrin extracellular matrix ligand fibronectin.

Osteoblast retraction induced by adherent neutrophils promotes osteoclast bone resorption: implication for altered bone remodeling in chronic gout.

Bone destruction in chronic gout is correlated with deposits of monosodium urate (MSU) crystals. Bone with MSU tophi were histopathologically shown to have altered remodeling and cellular distribution. We investigated the impact of neutrophils in bone remodeling associated with MSU and demonstrated that neutrophils, through elastase localized at their surface, induced retraction of confluent osteoblasts (OBs) previously layered on calcified matrix.

Extracellular nucleosides and nucleotides regulate liver functions via a complex system of membrane proteins.

Nucleosides and nucleotides are now considered as extracellular signalling molecules, like neurotransmitters and hormones. Hepatic cells, amongst other cells, ubiquitously express specific transmembrane receptors that transduce the physiological signals induced by extracellular nucleosides and nucleotides, as well as various cell surface enzymes that regulate the levels of these mediators in the extracellular medium. Here, we cover various aspects of the signalling pathways initiated by extracellular nucleosides and nucleotides in the liver, and discuss their overall impact on hepatic physiology.

The pronociceptive effect of proteinase-activated receptor-4 stimulation in rat knee joints is dependent on mast cell activation.

Proteinase-activated receptor-4 (PAR(4)) is a G-protein-coupled receptor activated by serine proteinases released during tissue repair and inflammation. We have previously shown that PAR(4) activation sensitises articular primary afferents leading to joint pain. This study examined whether mast cells contribute to this PAR(4)-induced sensitisation and consequent heightened pain behaviour.

Cytohesin-1 regulates fMLF-mediated activation and functions of the β2 integrin Mac-1 in human neutrophils.

The nucleotide exchange factor cytohesin-1 was previously reported to interact with the cytoplasmic domains of the integrin β-chain common to all β(2) integrins such as LFA-1 and Mac-1. We show here that cytohesin-1, which contributes to fMLF-induced functional responses in PMNs through activation of Arf6, restrains the activation of the β(2) integrin Mac-1 (αMβ(2)) in PMNs or dcAMP-differentiated PLB-985 cells. We found that the cytohesin-1 inhibitor SecinH3 or siRNA increased cell adhesion to immobilized fibrinogen and fMLF-mediated conformational changes of Mac-1, monitored using mAb CBRM1/5, specific for the activation epitope of the αM subunit.

Ectonucleotidases in the digestive system: focus on NTPDase3 localization.

Extracellular nucleotides and adenosine are biologically active molecules that bind members of the P2 and P1 receptor families, respectively. In the digestive system, these receptors modulate various functions, including salivary, gastric, and intestinal epithelial secretion and enteric neurotransmission. The availability of P1 and P2 ligands is modulated by ectonucleotidases, enzymes that hydrolyze extracellular nucleotides into nucleosides.

Inhibition of vascular ectonucleotidase activities by the pro-drugs ticlopidine and clopidogrel favours platelet aggregation.

Background And Purpose: After conversion to their active forms by the liver, ticlopidine and clopidogrel exert antiplatelet effects through irreversible inhibition of the P2Y₁₂ receptor. Concentrations of nucleotides such as ADP, the physiological agonist at platelet P2Y₁ and P2Y₁₂ receptors, are regulated by vascular ectonucleotidases, mainly nucleoside triphosphate diphosphohydrolase (NTPDase)1 and ecto-5'-nucleotidase. Here we evaluate the effect of these pro-drugs on vascular ectonucleotidase activity and on the natural function of these enzymes in regulating platelet aggregation.