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Direct Inhibitory Effect (direct + inhibitory_effect)
Selected AbstractsDirect Inhibitory Effect of Glucocorticoids on Corticotrophin-Releasing Hormone Gene Expression in Neurones of the Paraventricular Nucleus in Rat Hypothalamic Organotypic CulturesJOURNAL OF NEUROENDOCRINOLOGY, Issue 9 2008B. Bali Corticotrophin-releasing hormone (CRH) in the parvocellular neurosecretory neurones of hypothalamic paraventricular nucleus governs neuroendocrine stress cascade and is the major target of the negative feedback effect of corticosteroids. To assess whether glucocorticoids exert their inhibitory effect on CRH expression directly on parvocellular neurones or indirectly through a complex neuronal circuit, we examined the effect of corticosterone (CORT) and dexamethasone (DEX) on CRH mRNA levels in slice explant cultures of the rat hypothalamus. Organotypic slice cultures were prepared from 6 days old rat pups and maintained in vitro for 14 days. CRH mRNA expression was measured by in situ hybridisation histochemistry. Under basal conditions, CRH mRNA expressing cells were exclusively revealed in the paraventricular region along the third ventricle. Inhibition of action potential spike activity by tetrodotoxin (TTX, 1 ,m) reduced CRH mRNA signal in the organotypic cultures. CORT (500 nm) or DEX (50 nm) treatment for 24 h significantly inhibited CRH expression in the parvocellular neurones and this effect of corticosteroids was not affected following blockade of voltage dependent sodium channels by TTX. Forskolin-stimulated CRH mRNA levels in the paraventricular nucleus were also inhibited by CORT or DEX in the presence and in the absence of TTX. These studies identify paraventricular CRH neurones as direct target of corticosteroid feedback. Type II corticosteroid receptor agonists act directly on paraventricular neurones to inhibit basal and forskolin-induced CRH mRNA expression in explant cultures of the rat hypothalamus. [source] Relevance of a new rat model of osteoblastic metastases from prostate carcinoma for preclinical studies using zoledronic acidINTERNATIONAL JOURNAL OF CANCER, Issue 4 2008François Lamoureux Abstract Animal models that mimic osteoblastic metastases associated with prostate carcinoma are required to improve the therapeutic options in humans. A new model was then developed and characterized in immunocompetent rats. The bisphosphonate zoledronic acid (ZOL) was tested to validate this model as a therapeutic application. Rat AT6-1 prostate tumor cells were characterized in vitro at the transcriptional (bone and epithelial markers) and functional (induction of mineralized nodules) levels. The bone lesions induced after their direct injection into the femur bone marrow were characterized by radiography, microscanner and histology analyses. ZOL effects were studied in vivo on bone lesion development and in vitro on AT6-1 cell proliferation, apoptosis and cell cycle analysis. Apart from epithelial markers, AT6-1 cells express an osteoblast phenotype as they express osteoblastic markers and are able to induce mineralized nodule formation in vitro. A disorganization of the trabecular bone at the growth zone level was observed in vivo after intraosseous AT6-1 cell injection as well as cortical erosion. The tumor itself is associated with bone formation as revealed by SEM analysis and polarized light microscopy. ZOL prevents the development of such osteoblastic lesions, related to a direct inhibitory effect on tumor cell proliferation independent of caspase 3 activation, but associated with cell cycle arrest. A new rat model of osteoblastic bone metastases was validated in immunocompetent rats and used to show the relevance of using ZOL in such lesions, as this compound shows bifunctional effects on both bone remodelling and tumor cell proliferation. © 2007 Wiley-Liss, Inc. [source] Discovery of novel mechanisms and molecular targets for the inhibition of activated thrombin activatable fibrinolysis inhibitorJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2008K. HILLMAYER Summary.,Background:,Thrombin activatable fibrinolysis inhibitor (TAFI) is an important regulator of fibrinolysis and an attractive target to develop profibrinolytic drugs. Objective:,To analyze the (inhibitory) properties of five monoclonal antibodies (mAbs) directed towards rat TAFI (i.e. MA-RT13B2, MA-RT30D8, MA-RT36A3F5, MA-RT36B2 and MA-RT82F12). Methods and results:,Direct interference of the mAb with rat activated TAFI (TAFIa) activity was assayed using a chromogenic activity assay. This revealed reductions of 79% ± 1%, 54% ± 4%, and 19% ± 2% in activity in the presence of a 16-fold molar excess of MA-RT13B2, MA-RT36A3F5, and MA-RT82F12, respectively whereas MA-RT30D8 and MA-RT36B2 had no direct inhibitory effect. Additionally, MA-RT13B2 and MA-RT36A3F5 reduced rat TAFIa half-life by 56% ± 2% and 61% ± 3%. Tissue-type plasminogen activator mediated in vitro clot lysis was determined using rat plasma. Compared to potato tuber carboxypeptidase inhibitor, MA-RT13B2, MA-RT30D8, MA-RT36A3F5, and MA-RT82F12 reduced clot lysis times by 86% ± 14%, 100% ± 5%, 100% ± 10%, and 100% ± 11%, respectively. During epitope mapping, Arg227 and Ser251 were identified as major residues interacting with MA-RT13B2. Arg188 and His192 contribute to the interaction with MA-RT36A3F5. Arg227, Ser249, Ser251, and Tyr260 are involved in the binding of MA-RT30D8 and MA-RT82F12 with rat TAFI(a). The following mechanisms of inhibition have been deduced: MA-RT13B2 and MA-RT36A3F5 have a destabilizing effect on rat TAFIa whereas MA-RT30D8 and MA-RT82F12 partially block the access to the active site of TAFIa or interact with the binding of TAFIa to the blood clot. Conclusions:,The described inhibitory mAb towards rat TAFIa will facilitate TAFI research in murine models. Additionally, we reveal novel molecular targets for the direct inhibition of TAFIa through different mechanisms. [source] Host cell-mediated responses to infection with CryptosporidiumPARASITE IMMUNOLOGY, Issue 12 2000V. McDonald The coccidian Cryptosporidium infects epithelial cells of a variety of vertebrate hosts and is the causative agent of cryptosporidiosis. In mammals, including humans and domestic animals, C. parvum infects the gastrointestinal tract producing an acute watery diarrhoea and weight loss. CD4+ T-cell-deficient hosts have increased susceptibility to infection with the parasite and may develop severe life-threatening complications. The host responses which induce protective immunity and contribute to pathogenesis are poorly understood. In the immunological control of infection, recent studies with murine infection models suggest that IFN-, plays a key role in a partially protective innate immunity against infection identified in immunocompromised mice and also in the elimination of infection mediated by CD4+ T-cells. At the mucosal level, CD4+ intraepithelial lymphocytes are involved in the control of cryptosporidial infection, acting at least in part through production of IFN-, which has a direct inhibitory effect on parasite development in enterocytes. Primary infection of ruminants induces an intestinal inflammatory response in which increased numbers of various T-cell subpopulations appear in the villi. In addition, infection results in increased intestinal expression of pro-inflammatory cytokines such as IL-12, IFN-, and TNF-,. Because these cytokines appear to be important in the aetiology of inflammatory bowel disease, it is possible that they are involved in the mucosal pathogenesis of cryptosporidiosis. [source] Human cytomegalovirus induces a direct inhibitory effect on antigen presentation by monocyte-derived immature dendritic cellsBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2002Ulrich Grigoleit Summary. The hypothesis that productive infection of monocyte-derived immature dendritic cells (DCs) by the human cytomegalovirus (HCMV) is associated with decreased immunostimulatory capacity was tested in this study. DCs were infected with 60,80% efficiency by HCMV strain TB40/E. Infected versus uninfected cells were analysed by fluorescence-activated cell sorting and by immunocytochemistry for surface expression of major histocompatibility complex (MHC) and co-stimulatory molecules as well as cytokine secretion during the 3 d after infection. The immunostimulatory capacity of these cells was measured by mixed leucocyte reaction. In spite of the fact that HCMV infection of DCs induced an increased release of tumour necrosis factor-, (TNF-,) and a decreased interleukin 10 (IL-10) production, expression of MHC class I and II, as well as CD40 and CD80 molecules, were downregulated on infected DCs. The mixed leucocyte reaction showed significantly reduced immunostimulatory capacity of infected DC cultures. Simultaneous detection of MHC antigens and virus antigens by double immunofluorescence revealed that downregulation occurred only on infected cells, but not on uninfected bystander cells. These findings demonstrate on a single cell level, together with the marked downregulation of MHC and co-stimulatory molecules in the presence of high TNF-, and low IL-10 levels, a direct inhibitory effect of HCMV on antigen presentation by immature DCs independent of soluble mediators. [source] | ||||||||||