[Infections of implantable ports in haematology patients]. / Infections des chambres à cathéter implantables chez les patients atteints d'une hémopathie.

From 2010 to 2015, a study analysed the infections of implantable ports in haematology patients. Communication, collaboration and diligence were some of the main issues raised.

The PGE2-induced inhibition of the PLD activation pathway stimulated by fMLP in human neutrophils is mediated by PKA at the PI3-Kgamma level.

Prostaglandin E2 (PGE2), an eicosanoid that modulates inflammation, inhibits several chemoattractant-elicited functions in neutrophils such as chemotaxis, production of superoxide anions, adhesion, secretion of cytotoxic enzymes and synthesis of leukotriene B4. We previously reported that PGE2 inhibits the fMLP signaling pathway that leads to PLD activation through suppression of PI3-Kgamma activity and the decreased recruitment to membranes of PLD activation factors, PKC, Rho and Arf-GTPases. This effect is mediated via the EP2 receptors known to raise cAMP in cells. The inhibition of most fMLP-induced functional responses by PGE2 via EP2 receptors is mediated by PKA, except the chemotactic response. We have investigated the role of PKA in the EP2-mediated inhibition of the PLD activation pathway. H-89, a selective PKA pharmacological inhibitor suppressed the inhibitory effects of PGE2 at all stages of the PLD pathway activated by fMLP, i.e. PLD activity, translocation to membranes of PKCalpha, Rho and Arf-GTPases, calcium influx, tyrosine phosphorylation of proteins and finally translocation of p110gamma catalytic subunit of PI3-K to membranes. However, neither PLD nor PI3-Kgamma was substrate of PKA. These data provide evidence that PGE2-stimulated PKA activity regulates the PLD pathway stimulated by fMLP at the level of PI3-Kgamma and that the inhibition of PI3-Kgamma activation by PKA is a complex mechanism that remains to be completely elucidated.

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). In addition, PI-3Ks may be involved. The present study investigates the involvement of the PI-3K family in the mediation of the responses of human neutrophils to MSU crystals. The results obtained indicate that the interaction of MSU crystals with human neutrophils leads to the stimulation of class Ia PI-3Ks by a mechanism that is dependent on the tyrosine kinase Syk. We also found an increase in the amount of p85 associated with the Nonidet P-40-insoluble fraction derived from MSU crystal-stimulated human neutrophils. Furthermore, MSU crystals induce the formation of a complex containing p85 and Syk, which is mediated by the Src family kinases. Finally, evidence is also obtained indicating that the activation of PI-3Ks by MSU crystals is a critical element regulating phospholipase D activation and degranulation of human neutrophils. The latter response is likely to be involved in the joint and tissue damage that occurs in gouty patients.

Granulocyte macrophage-colony stimulating factor reduces the affinity of SHP-2 for the ITIM of CLECSF6 in neutrophils: a new mechanism of action for SHP-2.

Proteins that bear immunoreceptor tyrosine based inhibitory motifs (ITIM) are believed to participate in the repression of cell activation via phosphatases such as SHP-1, SHP-2 and/or SHIP-1. CLECSF6, also called DCIR, is a transmembrane protein expressed on leukocytes and predominantly on neutrophils that bears one ITIM pattern. This feature confers to CLECSF6 a role in the repression of cell activation. In order to better understand its role in neutrophil signalling, we analysed the binding of phosphatases to the ITIM of CLECSF6. We showed that a peptide bearing the ITIM of CLECSF6 in its phosphorylated form associates with both SHP-1 and SHP-2. Phosphorylated SHP-1 binds the ITIM whereas phosphorylated SHP-2 does not. In addition, granulocyte macrophage-colony stimulating factor (GM-CSF) reduces the binding of SHP-2 to the ITIM of CLECSF6 while enhancing the phosphorylation level of SHP-2. GM-CSF is known to recruit SHP-2 to its receptor. These data suggest that the phosphorylation of SHP-2 by GM-CSF promotes the binding of SHP-2 to the GM-CSF receptor to the disadvantage of CLECSF6. Therefore, upon a treatment with GM-CSF, SHP-2 could move from a CLECSF6 associated signalosome with a repressor function to a GM-CSF receptor associated signalosome with an activator function.

Prostaglandin E2 inhibits the phospholipase D pathway stimulated by formyl-methionyl-leucyl-phenylalanine in human neutrophils. Involvement of EP2 receptors and phosphatidylinositol 3-kinase gamma.

Prostaglandin E(2) (PGE(2)), originally discovered as a pro-inflammatory mediator, also inhibits several chemoattractant-elicited neutrophil functions, including adhesion, secretion of cytotoxic enzymes, production of superoxide anions, and chemotaxis. In this study, we have examined the effects of PGE(2) and prostaglandin E (EP) receptor-selective agonists/antagonists on several steps of the formyl-methionyl-leucyl-phenylalanine (fMLP)-induced phospholipase D (PLD) activation pathway in human neutrophils to elucidate the PGE(2) inhibitory mechanism. PGE(2) and EP(2) receptor agonists inhibited the stimulation of the activity of PLD induced by fMLP in a concentration-dependent manner. The fMLP-stimulated translocation to membranes of protein kinase C alpha, Rho, and Arf GTPases was diminished in the presence of PGE(2) or EP(2) agonists. Moreover, PGE(2) and EP(2) agonists decreased the activation of phosphatidylinositol 3-kinase gamma (PI3Kgamma) and Tec kinases as well as the tyrosine phosphorylation of proteins stimulated by fMLP. These data provide strong evidence that 1) the inhibitory effects of PGE(2) on the fMLP-induced PLD activation pathway were mediated via EP(2) receptors and that 2) the suppression of PI3Kgamma activity was the crucial step in the EP(2)-mediated inhibition of the fMLP-induced signaling cascade.

The ITIM-bearing CLECSF6 (DCIR) is down-modulated in neutrophils by neutrophil activating agents.

The recently discovered CLECSF6 protein displays the features of a receptor involved in the down-modulation of leukocyte activation. Although CLECSF6 has been the focus of the interest of many researchers lately, a Western blot characterization of the protein is still lacking. This highly reduces our ability to gain full knowledge of the biological relevance of this protein in cell responses. We produced two rabbit polyclonal antisera that detected a glycosylated protein at approximately 35kDa in neutrophils. Four different CLECSF6 mRNA species have been discovered to date. When deglycosylated, the protein displayed the molecular weight expected for the longest CLECSF6 form. Neutrophil membrane fractions were strongly enriched in the protein. We showed a down-modulation of the expression of this protein in neutrophils treated with granulocyte-macrophage-colony stimulating factor (GM-CSF), tumor necrosis factor (TNF-alpha), lipopolysaccharide (LPS), and interleukin (IL)-4. This work supports the hypothesis that CLECSF6 is involved in the control of inflammation in neutrophils.

Chemotactic factor-induced recruitment and activation of Tec family kinases in human neutrophils. II. Effects of LFM-A13, a specific Btk inhibitor.

Tyrosine phosphorylation events play major roles in the initiation and regulation of several functional responses of human neutrophils stimulated by chemotactic factors such as the bacterially derived tripeptide formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe). However, the links between the G protein-coupled receptors, the activation of the tyrosine kinases, and the initiation of neutrophil functional responses remain unclear. In the present study we assessed the effects of a Btk inhibitor, leflunomide metabolite analog (LFM-A13), on neutrophils. LFM-A13 decreased the tyrosine phosphorylation induced by fMet-Leu-Phe and inhibited the production of superoxide anions and the stimulation of adhesion, chemotaxis, and phospholipase D activity. We observed a decreased accumulation of phosphatidylinositol-3,4,5-trisphosphate in response to fMet-Leu-Phe in LFM-A13-pretreated cells even though the inhibitor had no direct effect on the lipid kinase activity of the p110 gamma or p85/p110 phosphatidylinositol 3-kinases or on the activation of p110 gamma by fMet-Leu-Phe. The phosphorylation of Akt and of extracellular signal-regulated kinases 1/2 and p38 were similarly inhibited by LFM-A13. LFM-A13 also negatively affected the translocation of Rac-2, RhoA, ADP ribosylation factor-1, Tec, Bmx, and Btk induced by fMet-Leu-Phe. The results of this study provide evidence for an involvement of Btk and possibly other Tec kinase family members in the regulation of the functional responsiveness of human neutrophils and link these events, in part at least, to the modulation of levels of phosphatidylinositol-3,4,5-trisphosphate.

Occupancy of adenosine A2a receptors promotes fMLP-induced cyclic AMP accumulation in human neutrophils: impact on phospholipase D activity and recruitment of small GTPases to membranes.

The aim of this study was to assess in human neutrophils the implication of an adenosine 3',5'-cyclic monophosphate (cAMP)-dependent pathway in the inhibitory effects of A2a receptor engagement. We found that Ro20-1724, a cAMP phosphodiesterase inhibitor, in the presence of adenosine deaminase (ADA) or A2a receptor antagonists rendered transient the fMLP-induced sustained increases in cAMP levels. The role of A2a receptor stimulation was demonstrated by the ability of the A2a receptor agonist, CGS21680, to prevent ADA-mediated reduction of the persistent cAMP elevation induced by fMLP. Persistent cAMP elevation correlated with inhibition of fMLP-induced PLD activation and recruitment of Arf, RhoA, and PKC to membranes. The suppressive effect of CGS21680 or isoproterenol, a beta-adrenergic receptor agonist, was increased by Ro20-1724 or by the adenylyl cyclase activator, forskolin, and reversed, at least in part, by the inhibitor of adenylyl cyclase, 2',5'-dideoxyadenosine. The activator of protein kinase A (PKA), Sp-cAMP inhibited fMLP-induced PLD activation and translocation of Arf and RhoA to membranes. In contrast, the suppression by A2a receptor stimulation of fMLP-induced PLD activation and cofactor recruitment was antagonized by PKA inhibitors, Rp-cAMP and H89. In conclusion, A2a receptor occupancy by extracellular adenosine inhibits fMLP-induced neutrophil activation via cAMP and PKA-regulated events.