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Mediated Inhibition (mediated + inhibition)
Selected AbstractsRoles of glutamate and GABA receptors in setting the developmental timing of spontaneous synchronized activity in the developing mouse cortexDEVELOPMENTAL NEUROBIOLOGY, Issue 12 2007Annette K. McCabe Abstract Spontaneous, synchronized electrical activity (SSA) plays important roles in nervous system development, but it is not clear what causes it to start and stop at the appropriate times. In previous work, we showed that when SSA in neonatal mouse cortex is blocked by TTX in cultured slices during its normal time of occurrence (E17,P3), it fails to stop at P3 as it does in control cultured slices, but instead persists through at least P10. This indicates that SSA is self-extinguishing. Here we use whole-cell recordings and [Ca2+]i imaging to compare control and TTX-treated slices to isolate the factors that normally extinguish SSA on schedule. In TTX-treated slices, SSA bursts average 4 s in duration, and have two components. The first, lasting about 1 s, is mediated by AMPA receptors; the second, which extends the burst to 4 s and is responsible for most of the action potential generation during the burst, is mediated by NMDA receptors. In later stage (P5,P9) control slices, after SSA has declined to about 4% of its peak frequency, bursts lack this long NMDA component. Blocking this NMDA component in P5,P9 TTX-treated slices reduces SSA frequency, but not to the low values found in control slices, implying that additional factors help extinguish SSA. GABAA inhibitors restore SSA in control slices, indicating that the emergence of GABAA -mediated inhibition is another major factor that helps terminate SSA. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source] Enhanced Anticonvulsant Activity of Neuroactive Steroids in a Rat Model of Catamenial EpilepsyEPILEPSIA, Issue 3 2001Doodipala S. Reddy Summary: ,Purpose: Perimenstrual catamenial epilepsy may in part be due to withdrawal of the endogenous progesterone-derived neurosteroid allopregnanolone that potentiates ,-aminobutyric acidA (GABAA) receptor,mediated inhibition. Here we sought to determine whether the anticonvulsant potencies of neuroactive steroids, benzodiazepines, phenobarbital (PB), and valproate (VPA) are altered during the heightened seizure susceptibility accompanying neurosteroid withdrawal in a rat model of perimenstrual catamenial epilepsy. Methods: Test drugs were evaluated for their ability to alter the convulsant activity of pentylenetetrazol (PTZ) in young adult female rats, in pseudopregnant rats with prolonged exposure to high levels of progesterone (and its neurosteroid metabolites), and in pseudopregnant rats 24 h after acute withdrawal of neurosteroids by treatment with the 5,-reductase inhibitor finasteride. Test drugs were administered at doses equivalent to twice their ED50 values for protection against PTZ-induced clonic seizures in naive young adult female rats. Results: The anticonvulsant activity of allopregnanolone (5 mg/kg, s.c.), pregnanolone (5 mg/kg, s.c.), allotetrahydrodeoxycorticosterone (15 mg/kg, s.c.), and tetrahydrodeoxycorticosterone (10 mg/kg, s.c.) were enhanced by 34,127% after neurosteroid withdrawal. The anticonvulsant activity of PB (65 mg/kg, i.p.) was also enhanced by 24% in neurosteroid-withdrawn animals. In contrast, the anticonvulsant activity of diazepam (4 mg/kg, i.p.), bretazenil (0.106 mg/kg, i.p.), and VPA (560 mg/kg, i.p.) were reduced or unchanged in neurosteroid-withdrawn animals. Conclusions: The anticonvulsant activity of neuroactive steroids is potentiated after neurosteroid withdrawal, supporting the use of such agents in the treatment of perimenstrual catamenial epilepsy. [source] IFN-,-mediated inhibition of antigen receptor-induced B cell proliferation and CREB-1 binding activity requires STAT-1 transcription factorEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2003Frank Frissora Abstract We report here a role for cyclic AMP-responsive element-binding protein-1 (CREB-1) in B cell antigen receptor (BCR)-induced growth inhibition by IFN-,. BCR-induced proliferation is negatively regulated by IFN-,. Stimulation through BCR resulted in dose-dependent induction of CREB-1 binding to the consensus cyclic AMP-responsive element. Recombinant IFN-, inhibited the BCR-induced CREB-1 DNA binding activity and cell proliferation in B cells from signal transducer and activator of transcription-1 (STAT-1)+/+, but not STAT-1,/, mice. These studies provide the first evidence for cross-talk between the STAT-1 and CREB-1 signaling pathways in IFN-,-mediated negative regulation of B cell activation. [source] N -methyl- d -aspartate, hyperpolarization-activated cation current (Ih) and ,-aminobutyric acid conductances govern the risk of epileptogenesis following febrile seizures in rat hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2010Mohamed Ouardouz Abstract Febrile seizures are the most common types of seizure in children, and are generally considered to be benign. However, febrile seizures in children with dysgenesis have been associated with the development of temporal lobe epilepsy. We have previously shown in a rat model of dysgenesis (cortical freeze lesion) and hyperthermia-induced seizures that 86% of these animals developed recurrent seizures in adulthood. The cellular changes underlying the increased risk of epileptogenesis in this model are not known. Using whole cell patch-clamp recordings from CA1 hippocampal pyramidal cells, we found a more pronounced increase in excitability in rats with both hyperthermic seizures and dysgenesis than in rats with hyperthermic seizures alone or dysgenesis alone. The change was found to be secondary to an increase in N -methyl- d -aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs). Inversely, hyperpolarization-activated cation current was more pronounced in naïve rats with hyperthermic seizures than in rats with dysgenesis and hyperthermic seizures or with dysgenesis alone. The increase in GABAA -mediated inhibition observed was comparable in rats with or without dysgenesis after hyperthermic seizures, whereas no changes were observed in rats with dysgenesis alone. Our work indicates that in this two-hit model, changes in NMDA receptor-mediated EPSCs may facilitate epileptogenesis following febrile seizures. Changes in the hyperpolarization-activated cation currents may represent a protective reaction and act by damping the NMDA receptor-mediated hyperexcitability, rather than converting inhibition into excitation. These findings provide a new hypothesis of cellular changes following hyperthermic seizures in predisposed individuals, and may help in the design of therapeutic strategies to prevent epileptogenesis following prolonged febrile seizures. [source] In vivo optical recordings of synaptic transmission and intracellular Ca2+ and Cl, in the superior colliculus of fetal ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2006Yoshiyuki Sakata Abstract Although the N -methyl- d -aspartate (NMDA) receptor is known to play a crucial role in activity-dependent remodeling of synaptic connections in the fetal superior colliculus (SC), its contribution to the electrical activity of fetal SC neurons has not been determined. Furthermore, whether ,-aminobutyric acid (GABA)-mediated inhibition occurs either as early as prenatal periods or only after eye opening has been controversial. We therefore performed optical recordings using voltage-, Ca2+ - and Cl, -sensitive fluorescent dyes to analyse synaptic transmission and changes in intracellular Ca2+ and Cl, in the SC of fetal rats that were still connected with the dams by the umbilical cord. Excitatory and inhibitory responses were evoked by focal SC stimulation. The excitatory synaptic responses are composed of early and late components. The early component was mediated by both non-NMDA and NMDA receptors, whereas the late component occurred mainly via NMDA receptors. Train pulse stimulation at higher currents was required for induction of the inhibition, which was antagonized by bicuculline, and blocking of the GABA-mediated inhibition by bicuculline uncovered masked excitatory synaptic responses. Focal SC stimulation induced increases in [Cl,]i and [Ca2+]i that were mediated by GABA-A receptors and mainly by NMDA receptors, respectively. GABA antagonists augmented SC-induced increases in [Ca2+]i. These results indicate that, in the fetal SC, excitatory and inhibitory synaptic transmissions occur before birth, that the NMDA receptor is a major contributor to excitatory synaptic transmission and increased [Ca2+]i, and that the GABA-A receptor is already functioning to inhibit excitatory neurotransmission. [source] Interferon-alpha regulates the dynamic balance between human activated regulatory and effector T cells: implications for antiviral and autoimmune responsesIMMUNOLOGY, Issue 1 2010Amit Golding Summary An adequate effector response against pathogens and its subsequent inactivation after pathogen clearance are critical for the maintenance of immune homeostasis. This process involves an initial phase of T-cell effector (Teff) activation followed by the expansion of regulatory T cells (Tregs), a unique cell population that limits Teff functions. However, significant questions remain unanswered about the mechanisms that regulate the balance between these cell populations. Using an in vitro system to mimic T-cell activation in human peripheral blood mononuclear cells (PBMC), we analysed the patterns of Treg and Teff activation, with special attention to the role of type I interferon (IFN-I). Interestingly, we found that IFN-,, either exogenously added or endogenously induced, suppressed the generation of CD4+ FoxP3HI IFN-,Neg activated Tregs (aTregs) while simultaneously promoting propagation of CD4+ FoxP3Low/Neg IFN-,Pos activated Teffs (aTeffs). We also showed that IFN-,-mediated inhibition of interleukin (IL)-2 production may play an essential role in IFN-,-induced suppression of aTregs. In order to test our findings in a disease state with chronically elevated IFN-,, we investigated systemic lupus erythematosus (SLE). Plasma from patients with SLE was found to contain IFN-I activity that suppressed aTreg generation. Furthermore, anti-CD3 activated SLE PBMCs exhibited preferential expansion of aTeffs with a very limited increase in aTreg numbers. Together, these observations support a model whereby a transient production of IFN-, (such as is seen in an early antiviral response) may promote CD4 effector functions by delaying aTreg generation, but a chronic elevation of IFN-, may tip the aTeff:aTreg balance towards aTeffs and autoimmunity. [source] Chronic exposure to sub-lethal beta-amyloid (A,) inhibits the import of nuclear-encoded proteins to mitochondria in differentiated PC12 cells*JOURNAL OF NEUROCHEMISTRY, Issue 5 2007Daniel Sirk Abstract Studies on amyloid beta (A,|), the peptide thought to play a crucial role in the pathogenesis of Alzheimer's disease, have implicated mitochondria in A,-mediated neurotoxicity. We used differentiated PC12 cells stably transfected with an inducible green fluorescent protein (GFP) fusion protein containing an N,-terminal mitochondrial targeting sequence (mtGFP), to examine the effects of sub-lethal A, on the import of nuclear-encoded proteins to mitochondria. Exposure to sub-lethal A,25,35 (10 ,mol/L) for 48 h inhibited mtGFP import to mitochondria; average rates decreased by 20 ± 4%. Concomitant with the decline in mtGFP, cytoplasmic mtGFP increased significantly while mtGFP expression and intramitochondrial mtGFP turnover were unchanged. Sub-lethal A,1,42 inhibited mtGFP import and increased cytoplasmic mtGFP but only after 96 h. The import of two endogenous nuclear-encoded mitochondrial proteins, mortalin/mtHsp70 and Tom20 also declined. Prior to the decline in import, mitochondrial membrane potential (mmp), and reactive oxygen species levels were unchanged in A,-treated cells versus reverse phase controls. Sustained periods of decreased import were associated with decreased mmp, increased reactive oxygen species, increased vulnerability to oxygen-glucose deprivation and altered mitochondrial morphology. These findings suggest that an A,-mediated inhibition of mitochondrial protein import, and the consequent mitochondrial impairment, may contribute to Alzheimer's disease. [source] Oestrogen Receptor ,: Role in Neurohypophyseal NeuronesJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2004C. D. Sladek Abstract The robust expression of oestrogen receptor , (ER-,) in magnocellular vasopressin neurones has focused attention on the role of this receptor and the gonadal steroids in the regulation of vasopressin secretion. Although the effects of gonadal steroids on vasopressin secretion have been the subject of many studies, there is no consensus in the literature as to their role. Possible reasons for the diverse findings are discussed, including diversity in the types, site and level of expression of steroid receptors across species, gender and physiological conditions. The physiological regulation of expression is of particular interest because ER-, mRNA expression in vasopressin neurones is inversely correlated to the osmotic state of the animal. Chronic hyperosmolality inhibits ER-, mRNA expression in magnocellular vasopressin neurones, while chronic hypo-osmolality enhances expression. This is consistent with an inhibitory role for ER-, because hyperosmolality is a potent stimulus for vasopressin secretion, whereas vasopressin secretion is maximally inhibited by chronic hypo-osmolality. An inhibitory role is also indicated by in vitro experiments demonstrating inhibition of osmotically stimulated vasopressin secretion by oestrogen and testosterone, and ER-, mediated inhibition of NMDA-stimulated vasopressin secretion. The challenge remains to elucidate the mechanism of this inhibition, and to understand its significance for maintenance of whole-body fluid and electrolyte homeostasis. [source] Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen: a novel mechanism for lipoprotein(a)-mediated inhibition of plasminogen activationJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008N. T. FERIC Summary.,Background:,Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for thrombotic disorders. Lp(a) is a unique lipoprotein consisting of a low-density lipoprotein-like moiety covalently linked to apolipoprotein(a) [apo(a)], a homologue of the fibrinolytic proenzyme plasminogen. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu-plasminogen to Lys-plasminogen. Objective:,Using acid,urea gel electrophoresis to resolve the two forms of radiolabeled plasminogen, we determined whether apo(a) is able to inhibit Glu-plasminogen to Lys-plasminogen conversion. Methods:,The assays were performed in the absence or presence of different recombinant apo(a) species, including point mutants, deletion mutants and variants that represent greater than 90% of the known apo(a) isoform sizes. Results:,Apo(a) substantially suppressed Glu-plasminogen conversion. Critical roles were identified for the kringle IV types 5,9 and kringle V; contributory roles for sequences within the amino-terminal half of the molecule were also observed. Additionally, with the exception of the smallest naturally-occurring isoform of apo(a), isoform size was found not to contribute to the inhibitory capacity of apo(a). Conclusion:,These findings underscore a novel contribution to the understanding of Lp(a)/apo(a)-mediated inhibition of plasminogen activation: the ability of the apo(a) component of Lp(a) to inhibit the key positive feedback step of plasmin-mediated Glu-plasminogen to Lys-plasminogen conversion. [source] Tryptophan catabolites regulate mucosal sensitization to ovalbumin in respiratory airwaysALLERGY, Issue 3 2009S. O. Odemuyiwa Background:, Indoleamine 2,3 dioxygenase (IDO), the rate-limiting enzyme in tryptophan catabolism, is important in generating tolerance at the foetal,maternal interface. Studies using 1-methyl-tryptophan (1-MT), the specific inhibitor of IDO, showed that this enzyme is important in interferon-gamma (IFN-,)-dependent inhibition of allergic inflammation in the respiratory airway during immunotherapy. Aims of study:, We investigated the role of IDO in the development of allergic sensitization, leading to allergic inflammation and airway hyper-responsiveness (AHR). Methods:, We used a mouse model to generate mucosal tolerance to lipopolysaccharide-free ovalbumin (OVA) following repeated intranasal inoculation of OVA over a 3-day period. We tested the successful induction of tolerance by subsequent intraperitoneal (i.p.) sensitization followed by intranasal challenge with OVA. A slow-release pellet of 1-MT implanted into mice was used to block IDO activity prior to repeated intranasal inoculation of OVA. We measured T-cell proliferation in response to OVA, determined airway inflammation, and measured AHR to intranasal methacholine to investigate the role of IDO in sensitization to OVA. Results:, Repeated intranasal administration of OVA generated tolerance and prevented a subsequent sensitization to OVA via the i.p. route. This response was inhibited in mice receiving a slow-release pellet of 1-MT. However, we successfully reconstituted tolerance in mice receiving 1-MT following intra-peritoneal injection of a mixture of kynurenine and hydroxyanthranilic acid. Conclusion:, Our data suggest that, in addition to their role in IFN-,-mediated inhibition of allergic airway inflammation, products of tryptophan catabolism play an important role in the prevention of sensitization to potential allergens in the respiratory airway. [source] Analysis of vitamin D-regulated gene expression in LNCaP human prostate cancer cells using cDNA microarraysTHE PROSTATE, Issue 3 2004Aruna V. Krishnan Abstract BACKGROUND 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] exerts growth inhibitory, pro-differentiating, and pro-apoptotic effects on prostate cells. To better understand the molecular mechanisms underlying these actions, we employed cDNA microarrays to study 1,25(OH)2D3 -regulated gene expression in the LNCaP human prostate cancer cells. METHODS mRNA isolated from LNCaP cells treated with vehicle or 50 nM 1,25(OH)2D3 for various lengths of time were hybridized to microarrays carrying approximately 23,000 genes. Some of the putative target genes revealed by the microarray analysis were verified by real-time PCR assays. RESULTS 1,25(OH)2D3 most substantially increased the expression of the insulin-like growth factor binding protein-3 (IGFBP-3) gene. Our analysis also revealed several novel 1,25(OH)2D3 -responsive genes. Interestingly, some of the key genes regulated by 1,25(OH)2D3 are also androgen-responsive genes. 1,25(OH)2D3 also down-regulated genes that mediate androgen catabolism. CONCLUSIONS The putative 1,25(OH)2D3 target genes appear to be involved in a variety of cellular functions including growth regulation, differentiation, membrane transport, cell,cell and cell,matrix interactions, DNA repair, and inhibition of metastasis. The up-regulation of IGFBP-3 gene has been shown to be crucial in 1,25(OH)2D3 -mediated inhibition of LNCaP cell growth. 1,25(OH)2D3 regulation of androgen-responsive genes as well as genes involved in androgen catabolism suggests that there are interactions between 1,25(OH)2D3 and androgen signaling pathways in LNCaP cells. Further studies on the role of these genes and others in mediating the anti-cancer effects of 1,25(OH)2D3 may lead to better approaches to the prevention and treatment of prostate cancer. © 2004 Wiley-Liss, Inc. [source] The programmed death 1/programmed death ligand 1 inhibitory pathway is up-regulated in rheumatoid synovium and regulates peripheral T cell responses in human and murine arthritisARTHRITIS & RHEUMATISM, Issue 7 2010Amalia P. Raptopoulou Objective T cells play a major role in the pathogenesis of rheumatoid arthritis (RA). The programmed death 1 (PD-1)/programmed death ligand 1 (PDL-1) pathway is involved in peripheral tolerance through inhibition of T cells at the level of synovial tissue. The aim of this study was to examine the role of PD-1/PDL-1 in the regulation of human and murine RA. Methods In synovial tissue and synovial fluid (SF) mononuclear cells from patients with RA, expression of PD-1/PDL-1 was examined by immunohistochemistry and flow cytometry, while PD-1 function was assessed in RA peripheral blood (PB) T cells after stimulation of the cells with anti-CD3 and PDL-1.Fc to crosslink PD-1. Collagen-induced arthritis (CIA) was induced in PD-1,/, C57BL/6 mice, and recombinant PDL-1.Fc was injected intraperitoneally to activate PD-1 in vivo. Results RA synovium and RA SF were enriched with PD-1+ T cells (mean ± SEM 24 ± 5% versus 4 ± 1% in osteoarthritis samples; P = 0.003) and enriched with PDL-1+ monocyte/macrophages. PD-1 crosslinking inhibited both T cell proliferation and production of interferon-, (IFN,) in RA patients; PB T cells incubated with RA SF, as well as SF T cells from patients with active RA, exhibited reduced PD-1,mediated inhibition of T cell proliferation at suboptimal, but not optimal, concentrations of PDL-1.Fc. PD-1,/, mice demonstrated increased incidence of CIA (73% versus 36% in wild-type mice; P < 0.05) and greater severity of CIA (mean maximum arthritis score 5.0 versus 2.3 in wild-type mice; P = 0.040), and this was associated with enhanced T cell proliferation and increased production of cytokines (IFN, and interleukin-17) in response to type II collagen. PDL-1.Fc treatment ameliorated the severity of CIA and reduced T cell responses. Conclusion The negative costimulatory PD-1/PDL-1 pathway regulates peripheral T cell responses in both human and murine RA. PD-1/PDL-1 in rheumatoid synovium may represent an additional target for immunomodulatory therapy in RA. [source] Estradiol inhibits chondrogenic differentiation of mesenchymal stem cells via nonclassic signalingARTHRITIS & RHEUMATISM, Issue 4 2010Zsuzsa Jenei-Lanzl Objective We undertook this study to examine the effects of estradiol on chondrogenesis of human bone marrow,derived mesenchymal stem cells (MSCs), with consideration of sex-dependent differences in cartilage repair. Methods Bone marrow was obtained from the iliac crest of young men. Density-gradient centrifugation,separated human MSCs proliferated as a monolayer in serum-containing medium. After confluence was achieved, aggregates were created and cultured in a serum-free differentiation medium. We added different concentrations of 17,-estradiol (E2) with or without the specific estrogen receptor inhibitor ICI 182.780, membrane-impermeable E2,bovine serum albumin (E2-BSA), ICI 182.780 alone, G-1 (an agonist of G protein,coupled receptor 30 [GPR-30]), and G15 (a GPR-30 antagonist). After 21 days, the aggregates were analyzed histologically and immunohistochemically; we quantified synthesized type II collagen, DNA content, sulfated glycosaminoglycan (sGAG) concentrations, and type X collagen and matrix metalloproteinase 13 (MMP-13) expression. Results The existence of intracellular and membrane-associated E2 receptors was shown at various stages of chondrogenesis. Smaller aggregates and significantly lower type II collagen and sGAG content were detected after treatment with E2 and E2-BSA in a dose-dependent manner. Furthermore, E2 enhanced type X collagen and MMP-13 expression. Compared with estradiol alone, the coincubation of ICI 182.780 with estradiol enhanced suppression of chondrogenesis. Treatment with specific GPR-30 agonists alone (G-1 and ICI 182.780) resulted in a considerable inhibition of chondrogenesis. In addition, we found an enhancement of hypertrophy by G-1. Furthermore, the specific GPR-30 antagonist G15 reversed the GPR-30,mediated inhibition of chondrogenesis and up-regulation of hypertrophic gene expression. Conclusion The experiments revealed a suppression of chondrogenesis by estradiol via membrane receptors (GPR-30). The study opens new perspectives for influencing chondrogenesis on the basis of classic and nonclassic estradiol signaling. [source] Evidence that Dkk-1 is dysfunctional in ankylosing spondylitisARTHRITIS & RHEUMATISM, Issue 1 2010Dimitrios Daoussis Objective Dkk-1 is an inhibitory molecule that regulates the Wnt pathway, which controls osteoblastogenesis. This study was undertaken to explore the potential role of Dkk-1 in ankylosing spondylitis (AS), a prototypical bone-forming disease. Methods Serum Dkk-1 levels were measured in 45 patients with AS, 45 patients with rheumatoid arthritis (RA), 15 patients with psoriatic arthritis (PsA), and 50 healthy subjects by sandwich enzyme-linked immunosorbent assay (ELISA). A functional ELISA was used to assess the binding of Dkk-1 to its receptor (low-density lipoprotein receptor,related protein 6). Furthermore, we studied the effect of sera from patients with AS and healthy subjects on the activity of the Wnt pathway in the Jurkat T cell model, with and without a neutralizing anti,Dkk-1 monoclonal antibody, by Western immunoblotting. Results Serum Dkk-1 levels were significantly increased in patients with AS (mean ± SEM 2,730 ± 135.1 pg/ml) as compared with normal subjects (P = 0.040), patients with RA (P = 0.020), and patients with PsA (P = 0.049). Patients with AS receiving anti,tumor necrosis factor , (anti-TNF,) treatment had significantly higher serum Dkk-1 levels than patients with AS not receiving such treatment (P = 0.007). Patients with AS studied serially prior to and following anti-TNF, administration exhibited a significant increase in serum Dkk-1 levels (P = 0.020), in contrast to patients with RA, who exhibited a dramatic decrease (P < 0.001). Jurkat cells treated with serum from AS patients exhibited increased Wnt signaling compared with cells treated with control serum. In that system, Dkk-1 blockade significantly enhanced Wnt signaling in control serum,treated, but not AS serum,treated, Jurkat T cells. Conclusion Our findings indicate that in patients with AS, circulating bone formation,promoting factors functionally prevail. This can be at least partially attributed to decreased Dkk-1,mediated inhibition. [source] Effects of cyclosporine on hematopoietic and immune functions in patients with hypoplastic myelodysplasiaCANCER, Issue 9 2002In vitro, in vivo studies Abstract BACKGROUND Immunosuppression may benefit some patients with hypoplastic myelodysplasia (HMDS) and refractory anemia (RA), but its mechanism of action is still obscure. METHODS Using flow cytometry, we studied Fas-receptor (Fas-R), Fas-ligand (Fas-L), and interferon-, (IFN-,) expression in CD34+ cells and lymphocytes obtained from 11 HMDS and 20 RA patients. In colony assays and long-term cultures, the effects of Fas triggering, IFN-, blockade, or cyclosporine(CsA) on the growth of hematopoietic progenitors (colony-forming cells [CFC]) were determined. The effects of CsA at daily doses of 1,3 mg/kg for at least 3 months in HMDS patients were also studied. RESULTS In basal conditions, committed and immature progenitor cells were found decreased in myelodysplastic (MDS) patients. No significant differences between HMDS and RA patients were detected. IFN-,,expressing CD4+ cells were significantly increased in HMDS patients, whereas intracytoplasmic Fas-L expression was only borderline elevated in CD3+ MDS cells. Increased numbers of CD34+ cells expressing Fas-R were found in HMDS and RA patients. CFC and secondary CFC showed higher susceptibility to Fas-L,mediated inhibition and the blockade of IFN-, improved marrow primary, but not secondary, CFC growth. CsA added in vitro to patient's lymphocytes significantly decreased the number of IFN-,,expressing CD4+ cells, but not Fas-L production. These effects were associated with increased colony formation. Similar to IFN-,blockade, production of secondary CFC was not enhanced by CsA. Administration of CsA to patients resulted in prolonged partial hematologic improvement in 8 of 11 HMDS patients. CONCLUSIONS Increased frequency of IFN-, producing CD4+ cells supports the involvement of lymphocyte-mediated suppression of hematopoiesis in the development of cytopenia in MDS patients. The ability of CsA to decrease in vitro IFN-, production may improve hematopoietic function, explaining the beneficial effect of this agent in HMDS patients. Cancer 2002;95:1911,22. © 2002 American Cancer Society. DOI 10.1002/cncr.10915 [source] High levels of oestrogen receptor-, in tumorigenesis: inhibition of cell growth and angiogenic factorsCELL PROLIFERATION, Issue 4 2001S. H. Ali We previously found that the stable overexpression of oestrogen receptor-, in the human endothelial cell line ECV304, inhibits its growth in vitro, and that this inhibition is possibly mediated through a down-regulation of the vasoactive agents endothelin-1 and vascular endothelial growth factor. Here we show an in vivo growth-inhibitory effect of oestrogen receptor-, overexpression in tumours initiated in nude mice from the same clone of ECV304. In addition, we show that this growth inhibition is accompanied by an ,v,3 -mediated inhibition of cell migration in vitro, and a down-regulation of the integrin ,v,3, vascular endothelial growth factor and vascularization in vivo. The levels of vascular endothelial growth factor and integrin ,v,3, through their effect on cell growth and migration, contribute to the process of angiogenesis and to the pathogenesis of atherosclerosis and cancer. The results shown here demonstrate that a higher level of oestrogen receptor-, in the cell, through its effect on certain angiogenic factors, may play a role in the control of angiogenesis. [source] Itraconazole-mediated inhibition of calcium entry into platelet-activating factor-stimulated human neutrophils is due to interference with production of leukotriene B4CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2007H. C. Steel Summary The primary objective of this study was to probe the involvement of leukotriene B4 (LTB4) in itraconazole (0·1,5 µM)-mediated inhibition of Ca2+ uptake by chemoattractant-activated human neutrophils. Following exposure of the cells to platelet-activating factor (PAF, 200 nM), LTB4 was measured by immunoassay, while neutrophil cytosolic Ca2+ concentrations were determined by a fura-2/AM-based spectrofluorimetric procedure. Activation of neutrophils was accompanied by an abrupt and sustained (for about 1 min) elevation in cytosolic Ca2+ which was associated with increased generation of LTB4, both of which were attenuated significantly by itraconazole at 0·5 µM and higher. The inhibitory effect of the anti-mycotic on Ca2+ uptake by PAF-activated cells was mimicked by an LTB4 antibody, as well as by LY255283 (1 µM) and MK886 (0·5 µM), an antagonist of LTB4 receptors and an inhibitor of 5,-lipoxygenase-activating protein, respectively, while addition of itraconazole to purified 5,-lipoxygenase resulted in inhibition of enzyme activity. A mechanistic relationship between itraconazole-mediated inhibition of LTB4 production and Ca2+ influx was also supported by the observation that pulsed addition of purified LTB4 to PAF-activated neutrophils caused substantial restoration of Ca2+ uptake by cells treated with the anti-mycotic. Taken together, these observations suggest that the potentially beneficial anti-inflammatory interactions of itraconazole with activated neutrophils result from interference with production of LTB4, with consequent attenuation of a secondary LTB4 -mediated wave of Ca2+ uptake by the cells. [source] | |||||||||||||