Biomedical subjects

Sylvia Forchap

Publications and source records attributed to Sylvia Forchap.

3 recordsLinked to original sources

PubMed2006

Stimulation of purinergic receptors modulates chemokine expression in human keratinocytes.

ATP is abundantly released from stressed or damaged cells in response to mechanical stimulation, bacteria, or noxious agents. In this study, we have investigated the possible involvement of P2 receptors (receptor for extracellular nucleotides) in the expression and release of inflammatory mediators by human keratinocytes. Notably, extracellular ATP displayed a complex regulation of IFN-gamma-stimulated chemokine expression, with upregulation of CC chemokine ligand 2 (CCL2), CCL5 and CXC chemokine ligand 8 (CXCL8), and suppression of the receptor CXC chemokine receptor 3 (CXCR3), CXCL9, CXCL10, and CXCL11. The effect of ATP was mimicked by ADP and adenosine-5'-O-3-thiotriphosphate, whereas 2',3'-O-(4-benzoylbenzoyl) ATP (BzATP) downmodulated all chemokines investigated. UTP had no effect on IFN-gamma-stimulated chemokine secretion. The broad-spectrum P2 receptor antagonist suramin and the selective P2Y1 inhibitor adenosine 3'-phosphate 5'-phosphosulfate counteracted the effect of ATP on secretion of all the chemokines examined, whereas pyridoxal phosphate 6-azophenyl 2',4'-disulfonic acid and KN62 (1-[N,O-bis(5-isoquinoline sulfonyl)-N-methyl-L-tyrosyl] 4 phenylpiperazine) partially prevented the inhibitory effect of ATP on CXCL10 secretion, but on the other hand potentiated the ATP-stimulatory effect on CCL5, CCL2, and CXCL8 release. In lesional skin of psoriasis and atopic dermatitis patients, intense P2X7 reactivity was confined to the cell membrane of the basal layer, whereas diffuse P2Y1 immunostaining was found throughout the epidermis. Collectively, our data suggest that the orchestrated activation of distinct P2Y and P2X receptors modulates skin inflammation.

Adenosine Triphosphate↗

PubMed2004

The antibiotic polymyxin B modulates P2X7 receptor function.

The natural peptide polymyxin B (PMB) is a well-known and potent antibiotic that binds and neutralizes bacterial endotoxin (LPS), thus preventing its noxious effects among LPS-mediated endotoxin shock in animal models. We have investigated the effect of PMB on responses mediated by the P2X(7)R in HEK293 and K562 cells transfected with P2X(7) cDNA and in mouse and human macrophages. In addition, in view of the potential exploitation of P2X(7)-directed agonists in antitumor therapy, we also investigated the effect of PMB in B lymphocytes from patients affected by chronic lymphocytic leukemia. PMB, at an optimal concentration dependent on the given cell type, greatly potentiated the effect of nucleotide-mediated P2X(7) stimulation. In particular, ATP-mediated Ca(2+) influx, plasma membrane permeabilization, and cytotoxicity were enhanced to an extent that, in the presence of PMB, cells were killed by otherwise ineffective nucleotide concentrations. The synergistic effect due to the combined application of ATP and PMB was prevented by incubation with the irreversible P2X blocker oxidized ATP (oATP), but not with the reversible antagonist 1-(N,O-bis(1,5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl)-4-phenilpiperazine (KN-62). Cells lacking P2X(7) were fully insensitive to the combined stimulation with PMB and ATP. Furthermore, PMB at the concentrations used had no untoward effects on cell viability. These results point to PMB as a useful tool for the modulation of P2X(7)R function and suggest that care should be used in the evaluation of ATP-stimulated immune cell responses in the presence of PMB as they may not solely be affected by removal of contaminating LPS.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed2004

Extracellular nucleotides are potent stimulators of human hematopoietic stem cells in vitro and in vivo.

Although extracellular nucleotides support a wide range of biologic responses of mature blood cells, little is known about their effect on blood cell progenitor cells. In this study, we assessed whether receptors for extracellular nucleotides (P2 receptors [P2Rs]) are expressed on human hematopoietic stem cells (HSCs), and whether activation by their natural ligands, adenosine triphosphate (ATP) and uridine triphosphate (UTP), induces HSC proliferation in vitro and in vivo. Our results demonstrated that CD34(+) HSCs express functional P2XRs and P2YRs of several subtypes. Furthermore, stimulation of CD34(+) cells with extracellular nucleotides caused a fast release of Ca(2+) from intracellular stores and an increase in ion fluxes across the plasma membrane. Functionally, ATP and, to a higher extent, UTP acted as potent early acting growth factors for HSCs, in vitro, because they strongly enhanced the stimulatory activity of several cytokines on clonogenic CD34(+) and lineage-negative CD34(-) progenitors and expanded more primitive CD34(+)-derived long-term culture-initiating cells. Furthermore, xenogenic transplantation studies showed that short-term preincubation with UTP significantly expanded the number of marrow-repopulating HSCs in nonobese diabetic/severe combined immunodeficiency mice. Our data suggest that extracellular nucleotides may provide a novel and powerful tool to modulate HSC functions.

Antigens, CD34↗