|
| ||
|
|
||
Acid Receptor (acid + receptor)
Kinds of Acid Receptor Selected AbstractsPossible Contribution of Central Gamma-Aminobutyric Acid Receptors to Resting Vascular Tone in Freely Moving RatsEXPERIMENTAL PHYSIOLOGY, Issue 5 2000Yumi Takemoto Previous studies have shown that central administration of GABA (gamma-aminobutyric acid), an inhibitory neurotransmitter, preferentially reduces hindquarters and carotid vascular resistances but not renal and coeliac vascular resistances in conscious rats. This study tested the hypothesis that these preferential actions of central GABA receptors are related to differences between vessels in resting autonomic vascular tone in freely moving rats. Rats were chronically implanted with intracisternal cannulas and/or electromagnetic probes to measure regional blood flows. In response to GABA administration, the changes in vascular resistance (arterial blood pressure/regional blood flow) of the hindquarters (n = 23) and carotid (n = 12) vascular beds were significantly and negatively correlated with basal vascular resistance. No such relationship was found for the renal (n = 21), coeliac (n = 13) and superior mesenteric (n = 23) vascular beds. This finding indicates that the responsiveness to GABA of brainstem pathways controlling the hindquarters and carotid vascular beds co-varies with resting resistance in hindquarters and carotid vessels. A similar analysis was performed, correlating the ongoing vascular resistance of each vessel with its response to ganglionic blockade by chlorisondamine. In this case, a significant negative correlation was also found for the hindquarters (n = 26) and carotid (n = 15) vascular beds, but not for the coeliac (n = 17) or superior mesenteric (n = 19) vessels. Together, these findings suggest that central GABA receptors accessible from the cisterna magna preferentially affect two vascular beds which, in the freely moving rat, show resting autonomic vascular tone. [source] Ethanol Impairs Activation of Retinoic Acid Receptors in Cerebellar Granule Cells in a Rodent Model of Fetal Alcohol Spectrum DisordersALCOHOLISM, Issue 5 2010Ambrish Kumar Background:, Ethanol is the main addictive and neurotoxic constituent of alcohol. Ethanol exposure during embryonic development causes dysfunction of the central nervous system (CNS) and leads to fetal alcohol spectrum disorders. The cerebellum is one of the CNS regions that are particularly vulnerable to ethanol toxic effects. Retinoic acid (RA) is a physiologically active metabolite of vitamin A that is locally synthesized in the cerebellum. Studies have shown that RA is required for neuronal development, but it remains unknown if ethanol impairs RA signaling and thus induces neuronal malformations. In this study, we tested the hypothesis that ethanol impairs the expression and activation of RA receptors in cerebellum and in cerebellar granule cells. Methods:, The cerebellum of ethanol unexposed and exposed pups was used to study the expression of retinoic acid receptors (RARs or RXRs) by immunohistochemistry and by Western blot analysis. We also studied the effect of ethanol on expression of RA receptors in the cerebellar granule cells. Activation of RA receptors (DNA-binding activities) in response to high-dose ethanol was determined by electrophoretic mobility shift and supershift assays. Results:, Findings from these studies demonstrated that ethanol exposure reduced the expression of RAR,/, while it increased the expression of RXR,/, in the cerebellum and in cerebellar granule neurons. Immuno-histological studies further strengthened the expression pattern of RA receptors in response to ethanol. The DNA-binding activity of RARs was reduced, while DNA-binding activity of RXRs was increased in response to ethanol exposure. Conclusion:, For the first time, our studies have demonstrated that high-dose ethanol affects the expression and activation of RA receptors, which could impair the signaling events and induce harmful effects on the survival and differentiation of cerebellar granule cells. Taken together, these findings could provide insight into the treatment options for brain defects caused by excessive ethanol exposure, such as in Fetal Alcohol Spectrum Disorders. [source] Identification of Darmstoff Analogues as Selective Agonists and Antagonists of Iysophosphatidic Acid Receptors.CHEMINFORM, Issue 16 2006Veeresa Gududuru Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Modular Solid-Phase Synthetic Approach To Optimize Structural and Electronic Properties of Oligoboronic Acid Receptors and Sensors for the Aqueous Recognition of OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2004Duane Stones Dr. Abstract This article describes the design and optimization of the first entirely modular, parallel solid-phase synthetic approach for the generation of well-defined polyamine oligoboronic acid receptors and fluorescence sensors for complex oligosaccharides. The synthetic approach allows an effective building of the receptor polyamine backbone, followed by the controlled diversification of the amine benzylic side chains. This approach enabled the testing, in a modular fashion, of the effect of different arylboronic acid units substituted with unencumbering para electron-withdrawing or electron-donating groups. The feasibility of this approach toward automated synthesis was also investigated with the assembly of a sublibrary of receptors by means of the Irori MiniKan technology. Several sublibraries of anthracene-capped sensors containing two or three arylboronic acids were synthesized, and their binding to a series of model disaccharides was examined in neutral aqueous media. The calculation of association constants by fluorescence titrations confirmed that subtle changes in the structures of the interamine spacers in the polyamine backbone can have a significant effect on the stability of the resulting complexes. Most importantly, this study led to the determination of the preferred electronic characteristics for the arylboronate units, and suggests that a new generation of receptors containing very electron-poor arylboronic acids could lead to a significant improvement of binding affinities. [source] Functional retinoid receptors in budding ascidiansDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2000Mika Kamimura A homolog of retinoid X receptors (RXR), named PmRXR, was cloned from the budding ascidian, Polyandrocarpa misakiensis. Gel-shift assays revealed that PmRXR and a previously identified P. misakiensis retinoic acid receptor (PmRAR) formed a complex to bind vertebrate-type retinoic acid response element (RARE). Transfection assays were carried out using a reporter gene containing a RARE upstream of lacZ. Two chimeric effector genes were constructed by placing PmRXR and PmRAR cDNA fragments (containing the DNA-binding, ligand-binding and ligand-dependent transactivation domains) downstream of the human RXR, and RAR, cDNA (covering the N-terminal coding region), respectively. Each chimeric cDNA was ligated to a notochord-specific enhancer. In case the embryos were transfected with all three transgenes and treated with retinoic acid (RA), the reporter gene was activated in the notochord cells. The result suggests that the PmRXR/PmRAR complex functions as an RA-dependent transcriptional activator. The PmRXR mRNA was detected in a mesenchymal cell type, called glomerulocyte, in the developing Polyandrocarpa bud. As this cell type has been shown to express PmRAR mRNA, it seems possible that the PmRXR/PmRAR complex mediates RA signaling in this cell type to induce the expression of genes involved in the morphogenesis of the developing bud. [source] Retinoic acid controls expression of tissue remodeling genes Hmgn1 and Fgf18 at the digit,interdigit junctionDEVELOPMENTAL DYNAMICS, Issue 2 2010Xianling Zhao Abstract Previous studies on retinoic acid receptor (RAR) mutants suggested that retinoic acid (RA) is required for loss of interdigital mesenchyme during digit formation. Here, we report that the RA-generating enzyme retinaldehyde dehydrogenase-2 (Raldh2) is expressed in the interdigital mesenchyme whereas Cyp26b1, controlling RA degradation, is expressed in digits, limiting autopodal RA action to the interdigital zones. Embryonic day 13.5 Raldh2,/, mouse embryos lose expression of the RARE-lacZ RA-reporter transgene and matrix metalloproteinase-11 (Mmp11) throughout the interdigital mesenchyme, while expression of RARb, Fgf18, and high mobility group N1 (Hmgn1) is lost at the digit,interdigit junction. Raldh2,/, autopods exhibit reduced interdigital apoptosis associated with loss of Bmp7 expression, but Bmp2, Bmp4, Msx2, and Fgf8 were unaffected. Although interdigital expression of Hmgn1 was greatly down-regulated in Raldh2,/, autopods, complementary expression of Sox9 in digit cartilage was unaffected. Regulation of Hmgn1 and Fgf18 at the digit,interdigit junction suggests RA controls tissue remodeling as well as apoptosis. Developmental Dynamics 239:665,671, 2010. © 2009 Wiley-Liss, Inc. [source] Further evidence for an association between the gamma-aminobutyric acid receptor A, subunit 4 genes on chromosome 4 and Fagerström Test for Nicotine DependenceADDICTION, Issue 3 2009Arpana Agrawal ABSTRACT Aims A previous association analysis identified polymorphisms in gamma-aminobutyric acid receptor A, subunit 4 (GABRA4) and GABRA2 to be associated with nicotine dependence, as assessed by a score of 4 or more on the Fagerström Test for Nicotine Dependence (FTND). In the present report, we extend the previous study by expanding our genotyping efforts significantly for these two genes. Design In 1049 cases (FTND of 4 or more) and 872 controls (smokers with FTND of 0) from the United States and Australia, we examine the association between 23 GABRA4 and 39 GABRA2 recently genotyped single nucleotide polymorphisms (SNPs) and nicotine dependence using logistic regression-based association analyses using the genomic analysis package PLINK. Results Two and 18 additional SNPs in GABRA4 and GABRA2, respectively, were associated with nicotine dependence. The SNPs identified in GABRA4 (P -value = 0.002) were restricted to introns 1 and 2, exon 1 and the 5, end of the gene, while those in GABRA2 localized to the 3, end of the gene and spanned introns 9,3, and were in moderate to high linkage disequilibrium (as measured by r2) with each other and with previously studied polymorphisms. Conclusion Our findings demonstrate consistently the role of GABRA4 and GABRA2 in nicotine dependence. However, further research is needed to identify the biological influence of these intronic variations and to isolate functionally relevant polymorphisms neighboring them. [source] Bidirectional synaptic plasticity as a consequence of interdependent Ca2+ -controlled phosphorylation and dephosphorylation pathwaysEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2003Pablo D'Alcantara Abstract Postsynaptic Ca2+ signals of different amplitudes and durations are able to induce either long-lasting potentiation (LPT) or depression (LTD). The bidirectional character of synaptic plasticity may result at least in part from an increased or decreased responsiveness of the glutamatergic ,-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPA-R) due to the modification of conductance and/or channel number, and controlled by the balance between the activities of phosphorylation and dephosphorylation pathways. AMPA-R depression can be induced by a long-lived Ca2+ signal of moderate amplitude favouring the activation of the dephosphorylation pathway, whereas a shorter but higher Ca2+ signal would induce AMPA-R potentiation resulting from the preferential activation of the phosphorylation pathway. Within the framework of a model involving calcium/calmodulin-dependent protein kinase II (CaMKII), calcineurin (PP2B) and type 1 protein phosphatase (PP1), we aimed at delineating the conditions allowing a biphasic U-shaped relationship between AMPA-R and Ca2+ signal amplitude, and thus bidirectional plasticity. Our theoretical analysis shows that such a property may be observed if the phosphorylation pathway: (i) displays higher cooperativity in its Ca2+ -dependence than the dephosphorylation pathway; (ii) displays a basal Ca2+ -independent activity; or (iii) is directly inhibited by the dephosphorylation pathway. Because the experimentally observed inactivation of CaMKII by PP1 accounts for this latter characteristic, we aimed at verifying whether a realistic model using reported parameters values can simulate the induction of either LTP or LTD, depending on the time and amplitude characteristics of the Ca2+ signal. Our simulations demonstrate that the experimentally observed bidirectional nature of Ca2+ -dependent synaptic plasticity could be the consequence of the PP1-mediated inactivation of CaMKII. [source] The bile acid receptor TGR5 (Gpbar-1) acts as a neurosteroid receptor in brainGLIA, Issue 15 2010Verena Keitel Abstract TGR5 (Gpbar-1) is a membrane-bound bile acid receptor in the gastrointestinal tract and immune cells with pleiotropic actions. As shown in the present study, TGR5 is also expressed in astrocytes and neurons. Here, TGR5 may act as a neurosteroid receptor, which is activated by nanomolar concentrations of 5,-pregnan-3,-ol-20-one and micromolar concentrations of 5,-pregnan-3,-17,-21-triol-20-one and 5,-pregnan-3,-ol-20-one (allopregnanolone). TGR5 stimulation in astrocytes and neurons is coupled to adenylate cyclase activation, elevation of intracellular Ca2+ and the generation of reactive oxygen species. In cultured rat astrocytes, TGR5 mRNA is downregulated in the presence of neurosteroids and ammonia already at concentrations of 0.5 mmol L,1. Furthermore, TGR5 protein levels are significantly reduced in isolated rat astrocytes after incubation with ammonia. A marked downregulation of TGR5 mRNA is also found in cerebral cortex from cirrhotic patients dying with hepatic encephalopathy (HE) when compared with brains from noncirrhotic control subjects. It is concluded that TGR5 is a novel neurosteroid receptor in brain with implications for the pathogenesis of HE. © 2010 Wiley-Liss, Inc. [source] Effects of proinflammatory cytokines on rat organic anion transporters during toxic liver injury and cholestasisHEPATOLOGY, Issue 2 2003Andreas Geier M.D. Hepatobiliary transporters are down-regulated in toxic and cholestatic liver injury. Cytokines such as tumor necrosis factor , (TNF-,) and interleukin 1, (IL-1,) are attributed to mediate this regulation, but their particular contribution in vivo is still unknown. Thus, we studied the molecular mechanisms by which Ntcp, Oatp1, Oatp2, and Mrp2 are regulated by proinflammatory cytokines during liver injury. Rats were injected intraperitoneally with either carbon tetrachloride or endotoxin. Inactivation of TNF-, and IL-1, was achieved by repetitive intraperitoneal injection of etanercept and anakinra, respectively. Messenger RNA (mRNA) levels of transporters and binding activities as well as nuclear protein levels of Ntcp, Oatp2, and Mrp2 transactivators were determined 20 to 24 hours later. In contrast to IL-1,, TNF-, inactivation alone fully prevented down-regulation of Ntcp, Oatp1, and Oatp2 mRNA as well as reduced binding activity of hepatocyte nuclear factor 1 (HNF-1) in CCl4 -induced toxic injury. In endotoxemia, down-regulation of Mrp2, and partially in case of Ntcp, could be prevented by IL-1, but not TNF-, blockade. However, inactivation of either cytokine led to preservation of HNF1 and partially of retinoid X receptor/retinoic acid receptor (RXR/RAR) binding activity. No effect of anticytokines was seen on pregnane X receptor (PXR) and constitutive androstane receptor (CAR) binding activity as well as nuclear protein mass. In conclusion, TNF-, represents the master cytokine responsible for HNF1-dependent down-regulation of Ntcp, Oatp1, and Oatp2 in CCl4 -induced toxic liver injury. IL-1, predominates in a complex signaling network of Ntcp and Mrp2 regulation in cholestatic liver injury. In contrast to in vitro studies, HNF1 and RXR/RAR-independent mechanisms appear to be more important in regulation of Mrp2 and Ntcp gene expression in endotoxemia. [source] Aberrant methylation of multiple genes in the upper aerodigestive tract epithelium of heavy smokersINTERNATIONAL JOURNAL OF CANCER, Issue 4 2003Sabine Zöchbauer-Müller Abstract An important method for silencing tumor suppressor genes in cancers is by aberrant methylation (referred to as methylation) of CpG islands in gene promoter regions. In lung cancer, methylation of the genes retinoic acid receptor ,-2 (RAR,- 2), CDH13 (H-cadherin), p16INK4a (p16), RASSF1A (RAS association domain family I) is frequent. Thus, we investigated methylation of these genes in 4 different types of specimens (oropharyngeal brushes, sputum samples, bronchial brushes and bronchioloalveolar lavage [BAL] samples) of the upper aerodigestive tract epithelium from heavy smokers without evidence of cancer but with morphometric evidence of sputum atypia and compared the frequencies of methylation in the different types of specimens. In addition, we also analyzed sputum samples from 30 never smokers for methylation of these genes. Our major findings are: (i) At least one gene was methylated in one or more specimens from 48% of the smokers. However, methylation was statistically significant less frequently in never smokers compared to smokers. (ii) In general, methylation occurred more frequently in samples from the central airways (sputum, bronchial brushes) compared to the peripheral airways (BAL) and only occasionally in the oropharynx. (iii) RAR,- 2 was the most frequently methylated gene, whereas the frequency of methylation for the other genes was lower. (iv) Data from sputum samples and bronchial brushes were comparable. Our findings suggest that detection of methylation should be investigated as an intermediate marker for lung cancer risk assessment and response to chemopreventive regimens. © 2003 Wiley-Liss, Inc. [source] Expression of retinoic acid receptor , in dermatofibrosarcoma protuberansJOURNAL OF CUTANEOUS PATHOLOGY, Issue 11 2009Zhou Xiaoli Background:, Retinoic acid receptor , (RAR ,) has been shown to act as a tumor suppressor in many solid human tumors. To investigate the putative role of RAR , in dermatofibrosarcoma protuberans (DFSP), we examined the expression of RAR , in DFSPs and analyzed the correlation of expression patterns between RAR , and cyclooxygenase (COX)-2 as well as clinicopathological variables. Methods:, Using tissue microarray and immunohistochemistry, we evaluated nuclear RAR , staining and cytoplasm COX-2 staining in 53 DFSPs. Results:, 48 DFSPs (90.58%) were immunopositive for RAR ,, while 32 DFSPs (60.38%) were immunopositive for COX-2. RAR , staining was significantly inversely correlated with COX-2 staining (p < 0.001; r =,0.668). Conclusions:, Our data indicated that RAR , expressed in DFSPs and correlated with COX-2 expression. RAR , may be a potential therapeutic target for unresectable DFSP cases. [source] A new method for the synthesis and herbicidal activity of 3-phenoxy-6-(1H- (substituted)pyrazol-1-yl) pyridazinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2009Fang-Zhong Hu A series of 3-substituted phenoxy-6-((substituted)1H -pyrazol-1-yl) pyridazines were synthesized from the condensation of various phenols and 3-chloro-6-(1H -pyrazol-1-yl) pyridazine 2 or 3-chloro-6-(5,-methyl-4-ethoxycarbonyl- 1H -pyrazol-1-yl) pyridazine 6 in N,N-dimethylformamide (DMF) at 120°C with K2CO3 as an acid receptor. The intermediates 2 or 6 were obtained from the cyclization of 3-chloro-6-hydrazinyl pyridazine 1 with 3-dimethylamino-acrylaldehyde or ethyl 2-((dimethylamino) methylene)-3-oxobutanoate in n -butanol under reflux, respectively, and side products 3 or 7 were also generated. All of the title compounds were confirmed by 1H NMR, infrared spectometry (IR) and elemental analyses. Preliminary bioassay indicated that some of the title compounds showed high inhibitory activity against Brassica campestris L. (B. campestris) and moderate inhibitory activity against Echinochloa crusgalli. For example, the inhibition percentages of compound 4b and 4c against B. campestris were both 94% at 10 ,g/mL. J. Heterocyclic Chem., (2009). [source] Nicotinic acid: the broad-spectrum lipid drug.JOURNAL OF INTERNAL MEDICINE, Issue 2 2005A 50th anniversary review Abstract. Nicotinic acid has, like the Roman God Janus, two faces. One is the vitamin. The other is the broad-spectrum lipid drug. The Canadian pathologist Rudolf Altschul discovered 50 years ago that nicotinic acid in gram doses lowered plasma levels of cholesterol. From the point of view of treatment of the dyslipidaemias that are risk factors for clinical atherosclerosis nicotinic acid is a miracle drug. It lowers the levels of all atherogenic lipoproteins , VLDL and LDL with subclasses as well as Lp(a) , and in addition it raises more than any other drug the levels of the protective HDL lipoproteins. Trials have shown that treatment with nicotinic acid reduces progression of atherosclerosis, and clinical events and mortality from coronary heart disease. The new combination treatment with statin-lowering LDL and nicotinic acid-raising HDL is reviewed. A basic effect of nicotinic acid is the inhibition of fat-mobilizing lipolysis in adipose tissue leading to a lowering of plasma free fatty acids, which has many metabolic implications which are reviewed. The very recent discovery of a nicotinic acid receptor and the finding that the drug stimulates the expression of the ABCA 1 membrane cholesterol transporter have paved the way for exciting and promising new 50 years in the history of nicotinic acid. [source] NSF binds calcium to regulate its interaction with AMPA receptor subunit GluR2JOURNAL OF NEUROCHEMISTRY, Issue 6 2007Jonathan G. Hanley Abstract N -ethylmaleimide-sensitive fusion protein (NSF) is essential for numerous Ca2+ -triggered vesicle trafficking events. It functions as a molecular chaperone to regulate trafficking protein complexes such as the soluble NSF attachment protein (SNAP) receptor complex and the ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-protein interacting with C-kinase (PICK1) complex. AMPAR trafficking is fundamental to processes of synaptic plasticity, which may underlie learning and memory. Changes in synaptic strength brought about by AMPAR trafficking are triggered by a post-synaptic influx of Ca2+, which may have numerous molecular targets including PICK1. NSF binds AMPAR subunit glutamate receptor subunit 2 (GluR2) and functions to maintain receptors at the synapse. In this study, it was showed that NSF is a Ca2+ -binding protein and that GluR2,NSF interactions are inhibited by the presence of 15 ,mol/L Ca2+. NSF Ca2+ -binding is reciprocally inhibited by the presence of GluR2 C-terminus. Mutant of NSF that binds Ca2+ with reduced affinity and binds GluR2 with reduced sensitivity to Ca2+ was identied. In addition, the interaction of ,SNAP with PICK1 is sensitive to Ca2+. This study demonstrates that the GluR2-NSF-,SNAP-PICK1 complex is regulated directly by Ca2+, allowing for the transduction of Ca2+ signals into concerted alterations in protein,protein interactions to bring about changes in AMPAR trafficking during synaptic plasticity. [source] Ethanol Attenuates the HFS-Induced, ERK-Mediated LTP in a Dose-Dependent Manner in Rat StriatumALCOHOLISM, Issue 1 2009Gui Qin Xie Background:, The striatum has been implicated to play a role in the control of voluntary behavior, and striatal synaptic plasticity is involved in instrumental learning. Ethanol is known to alter synaptic plasticity, in turn altering the behavior of human and animals. However, it remains unclear whether the striatum plays a role in the effects of ethanol on the central nervous system. The objective of this investigation was to study the effects of acute perfusion of ethanol on long-term potentiation (LTP) to elucidate the mechanisms of addictive drugs in the striatum. In addition, we investigated the contribution of intracellular extracellular signal regulated protein kinase (ERK) signaling pathway to corticostriatal LTP induction. Methods:, The stimulation evoked population spikes (PS) were recorded from the dorsomedial striatum (DMS) slices of rat using the extracellular recording technique. The LTP in DMS slices was induced by high-frequency stimulation (HFS). The ERK level of the DMS was assessed with the Western blot technique. Results:, U0126, the inhibitor of ERK, eliminated or significantly attenuated the LTP induced by HFS of the PS in the DMS. MK801 and APV, N -methyl- d -aspartic acid receptor (NMDAR) antagonists, inhibited the induction of striatal LTP, and HFS-induced ERK activation decreased in the slices treated with MK801 in the DMS. Clinically relevant concentrations of ethanol (22 to 88 mM) dose-dependently attenuated the HFS-induced striatal LTP and ERK activation in this brain region. Conclusions:, The LTP of the PS in the DMS is, at least partly, mediated by the ERK pathway coupling to NMDARs. Ethanol attenuated the HFS-induced, ERK-mediated LTP in a dose-dependent manner in this brain region. These results indicate that ethanol may change the synaptic plasticity of corticostriatal circuits underlying the learning of goal-directed instrumental actions, which is mediated by an intracellular ERK signaling pathway associated with NMDARs. [source] Retinoic acid signalling induces the differentiation of mouse fetal liver-derived hepatic progenitor cellsLIVER INTERNATIONAL, Issue 10 2009Jiayi Huang Abstract Background: Hepatic progenitor cells (HPCs) can be isolated from fetal liver and extrahepatic tissues. Retinoic acid (RA) signalling plays an important role in development, although the role of RA signalling in liver-specific progenitors is poorly understood. Aims: We sought to determine the role of RA in regulating hepatic differentiation. Methods: RNA was isolated from liver tissues of various developmental stages. Liver marker expression was assessed by reverse transcriptase-polymerase chain reaction and immunofluorescence staining. Reversibly immortalized HPCs derived from mouse embryonic day 14.5 (E14.5) liver (aka, HP14.5) were established. Albumin promoter-driven reporter (Alb-GLuc) was used to monitor hepatic differentiation. Glycogen synthesis was assayed as a marker for terminal hepatic differentiation. Results: Retinoic acid receptor (RAR)-,, retinoid X receptor (RXR)-, and RXR-, expressed in E12.5 to postnatal day 28 liver samples. Expression of RAR-, and RXR-, was low perinatally, whereas RAR-, was undetectable in prenatal tissues and increased postnatally. Retinal dehydrogenase 1 and 2 (Raldh1 and Raldh2) were expressed in all tissues, while Raldh3 was weakly expressed in prenatal samples but was readily detected postnatally. Nuclear receptor corepressors were highly expressed in all tissues, while expression of nuclear co-activators decreased in perinatal tissues and increased after birth. HP14.5 cells expressed high levels of early liver stem cell markers. Expression of RA signalling components and coregulators was readily detected in HP14.5. RA was shown to induce Alb-GLuc activity and late hepatocyte markers. RA was further shown to induce glycogen synthesis in HP14.5 cells, an important function of mature hepatocytes. Conclusions: Our results strongly suggest that RA signalling may play an important role in regulating hepatic differentiation. [source] Chemical genomics: Functional analysis of orphan nuclear receptors in the regulation of bile acid metabolismMEDICINAL RESEARCH REVIEWS, Issue 6 2001Timothy M. Willson Abstract Chemical genomics is the name we have given to the analysis of gene function through use of small molecule chemical tools. Orphan nuclear receptors are ideally suited to this technique of functional analysis, since their activity as transcription factors is regulated by small hydrophobic ligands. GW4064 is a potent and selective nonsteroidal ligand for the nuclear bile acid receptor FXR (NR1H4). Using GW4064 as a chemical tool, we have identified genes regulated by FXR in the liver, including those involved in bile acid synthesis and transport. We have also discovered that PXR (NR1I2) is a lithocholic acid receptor that controls the biosynthesis and metabolism of bile acids. Together FXR and PXR cooperate to control biliary and urinary bile acid excretion. These functions suggest that potent PXR and FXR ligands may offer a new approach to the treatment of cholestatic liver disease. © 2001 John Wiley & Sons, Inc. Med Res Rev, 21, No. 6, 513,522, 2001 [source] Retinoids and retinoic acid receptors regulate growth arrest and apoptosis in human mammary epithelial cells and modulate expression of CBP/p300MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2002Eric C. Dietze Abstract Retinoids and retinoic acid receptors (RARs) are important mediators of normal epithelial cell homeostasis. To assess the role of retinoids and RARs in regulating growth arrest and apoptosis in benign and malignant mammary epithelial cells, two model systems were developed: 1) RAR function was suppressed in retinoid-sensitive normal human mammary epithelial cells (HMECs) by the dominant-negative retinoic acid receptor, RAR,403 (DNRAR), and 2) retinoid-resistant MCF-7 breast cancer cells were transduced with a functional RAR,2. Inhibition of RAR function by the DNRAR in HMECs resulted in retinoid-resistance, increased proliferation, and dysregulated growth when cells were cultured in reconstituted extracellular matrix (rECM). Expression of RAR,2 in MCF-7 cells resulted in sensitivity to retinoid-induced growth arrest and apoptosis. The CREB-binding protein (CBP) and the homologous protein p300 are tightly regulated, rate-limiting integrators of diverse signaling pathways and are recruited during retinoid-mediated transcriptional activation. The relationship between retinoid receptor expression, growth regulation, and transcriptional regulation of CBP/p300 is poorly understood. Inhibition of RAR function in HMECs by DNRAR suppressed expression of CBP/p300 and expression of RAR,2 in MCF-7 cells promoted induction of CBP/p300 when cells were treated with 1.0 ,M all- trans -retinoic acid (ATRA). These results suggest that ATRA and RARs regulate growth arrest of HMECs and modulate CBP/p300 protein expression. Since CBP and p300 are normally present in limiting amounts, their regulation by ATRA and RARs may be an important element in the control of transcriptional activation of genes regulating growth arrest and apoptosis. Microsc. Res. Tech. 59:23,40, 2002. © 2002 Wiley-Liss, Inc. [source] Missing link identified: GpBAR1 is a neuronal bile acid receptorNEUROGASTROENTEROLOGY & MOTILITY, Issue 7 2010S. J. Keely Abstract,In addition to their classical functions in aiding the digestion and absorption of lipids, bile acids are increasingly gaining appreciation for their roles in regulating intestinal physiology. Bile acids are now widely considered as hormones that exert a wide range of physiological and pathophysiological effects both within and outside the gastrointestinal (GI) tract. The discovery of the bile acid receptor, GpBAR1, represented a major step forward in our understanding of how cells can sense and respond to bile acids. GpBAR1 is a cell surface G protein-coupled receptor expressed on adipose tissue and skeletal muscle where it has been found to be an important regulator of cellular metabolism. In a paper published in the current issue of Neurogastroenterology and Motility, Poole et al. investigated the expression and function of GpBAR1 in mouse intestine. They found the receptor to be expressed throughout the GI tract but predominantly on nerves within the myenteric and submucosal plexuses. Employing in vitro and in vivo techniques they demonstrated that activation of GpBAR1 by bile acids inhibits small and large intestinal motor function and delays intestinal transit. The effects of GpBAR1 activation are mediated through activation of cholinergic and nitrergic interneurons. The data reported by Poole et al. provides novel and exciting insights into how bile acids exert their actions in the intestine. This Editorial Viewpoint aims to further consider the potential physiological and pathophysiological implications of their findings. [source] Nuclear receptors of the enteric tract: guarding the frontierNUTRITION REVIEWS, Issue 2008Daniel R Schmidt In addition to its classical role in mineral homeostasis, the vitamin D receptor has been implicated in diverse physiologic and pathophysiologic processes including immunoregulation and cancer. Interestingly, the vitamin D receptor has been evolutionarily and functionally linked to a select group of nuclear receptors based on a common organism-wide tissue expression profile. These members of the nuclear receptor superfamily, which include the bile acid receptor, xenobiotic receptors, and several orphan nuclear receptors, comprise a transcriptional regulatory network that functions in nutrient uptake, xenobiotic metabolism, and mucosal protection. The major homeostatic functions of the enteric nuclear receptor network are the topic of this review. [source] In vivo imaging of retinoic acid receptor ,2 transcriptional activation by the histone deacetylase inhibitor MS-275 in retinoid-resistant prostate cancer cellsTHE PROSTATE, Issue 1 2005David Z. Qian Abstract BACKGROUND In retinoid resistant epithelial tumors, the lack of retinoic acid receptor ,2 (RAR,2) expression due to epigenetic silencing impairs the activation of retinoid target genes including RAR,2, and has been associated with the development of cancer. In this study we developed a strategy to monitor the re-activation of RAR,2 by chromatin remodeling agents combined with retinoids in real time, and to correlate the RAR,2 re-activation with anti-tumor activity. METHODS We selected the RAR,2-negative retinoid resistant human prostate carcinoma cell line PC3 and stably transfected it with a luciferase expression vector under the control of a functional segment of RAR,2 promoter (pGL2-RAR,2-PC3). Then, we used the bioluminescence technology to monitor the reporter gene expression in real time both in vitro and in vivo following combination treatment with the histone deacetylase inhibitor MS-275 and 13- cis retinoic acid (CRA). Based on the effective dose for the RAR,2 re-activation, we tested the anti-tumor activity of this drug combination. RESULTS Following combination treatment with MS-275 and CRA, we observed endogenous RAR,2 re-expression, acetylation at the RAR,2 promoter level, and synergistic activation of the luciferase reporter gene by real time imaging both in vitro and in vivo. Combination treatment with MS-275 and CRA restored retinoid sensitivity in human prostate carcinoma cell lines, and had a greater inhibitory effect on tumor cell growth than single agents in vitro and in vivo. CONCLUSIONS This study provides evidence that HDAC inhibitors restore retinoid sensitivity in prostate cancer cells, and in vivo real time imaging of RAR,2 activation may represent a useful tool to study the pharmacodynamics of combination therapy with HDAC inhibitors and retinoids. © 2005 Wiley-Liss, Inc. [source] AMPA receptor antibodies in limbic encephalitis alter synaptic receptor location,ANNALS OF NEUROLOGY, Issue 4 2009Meizan Lai MD Objective To report the clinical and immunological features of a novel autoantigen related to limbic encephalitis (LE) and the effect of patients' antibodies on neuronal cultures. Methods We conducted clinical analyses of 10 patients with LE. Immunoprecipitation and mass spectrometry were used to identify the antigens. Human embryonic kidney 293 cells expressing the antigens were used in immunocytochemistry and enzyme-linked immunoabsorption assay. The effect of patients' antibodies on cultures of live rat hippocampal neurons was determined with confocal microscopy. Results Median age was 60 (38,87) years; 9 were women. Seven had tumors of the lung, breast, or thymus. Nine patients responded to immunotherapy or oncological therapy, but neurological relapses, without tumor recurrence, were frequent and influenced the long-term outcome. One untreated patient died of LE. All patients had antibodies against neuronal cell surface antigens that by immunoprecipitation were found to be the glutamate receptor 1 (GluR1) and GluR2 subunits of the ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Human embryonic kidney 293 cells expressing GluR1/2 reacted with all patients' sera or cerebrospinal fluid, providing a diagnostic test for the disorder. Application of antibodies to cultures of neurons significantly decreased the number of GluR2-containing AMPAR clusters at synapses with a smaller decrease in overall AMPAR cluster density; these effects were reversed after antibody removal. Interpretation Antibodies to GluR1/2 associate with LE that is often paraneoplastic, treatment responsive, and has a tendency to relapse. Our findings support an antibody-mediated pathogenesis in which patients' antibodies alter the synaptic localization and number of AMPARs. Ann Neurol 2009;65:424,434 [source] Ligands for retinoic acid receptors are elevated in osteoarthritis and may contribute to pathologic processes in the osteoarthritic jointARTHRITIS & RHEUMATISM, Issue 6 2009Mark R. Davies Objective Vitamin A derivatives, including all- trans -retinoic acid (ATRA), have a well-established role during skeletal development and limb formation and have been shown to have profound effects on chondrocyte phenotype. The aim of this study was to elucidate the effects of retinoids and components of the retinoid metabolic pathway on chondrocyte phenotype in the tibiofemoral joints of patients with osteoarthritis (OA), to show that the retinoids can have multiple effects relevant to the OA disease process. Methods Human explant tissue and a chondrocyte-like cell line were treated with ATRA, and the responses of 4 key markers of chondrocyte phenotype were analyzed. In addition, the effects of ATRA on a number of novel genes associated with OA were assessed using a low-density microarray containing 80 disease marker genes. Results Vitamin A metabolite levels were elevated in synovial fluid, serum, and cartilage from patients with OA. Expression profiling of a retinoic acid receptor , coactivator protein, P/CAF, demonstrated elevated expression in patients with OA, suggesting the potential for increased signaling via the retinoid receptors in the disease. ATRA increased the levels of matrix metalloproteinase 13 and aggrecanase activity in human cartilage explants and in a human chondrocyte cell line. Furthermore, ATRA altered the expression of a wide range of relevant genes, including the types I, II, IX, and XI collagen genes, toward a nonchondrogenic and OA-like phenotype. Conclusion These results suggest that retinoid signaling could have a central role in OA, and that components of the pathway may provide potential disease biomarkers or targets for therapeutic intervention. [source] Functional characterization of hypertrophy in chondrogenesis of human mesenchymal stem cellsARTHRITIS & RHEUMATISM, Issue 5 2008Michael B. Mueller Objective Mesenchymal stem cells (MSCs) are promising candidate cells for cartilage tissue engineering. Expression of cartilage hypertrophy markers (e.g., type X collagen) by MSCs undergoing chondrogenesis raises concern for a tissue engineering application for MSCs, because hypertrophy would result in apoptosis and ossification. To analyze the biologic basis of MSC hypertrophy, we examined the response of chondrifying MSCs to culture conditions known to influence chondrocyte hypertrophy, using an array of hypertrophy-associated markers. Methods Human MSC pellet cultures were predifferentiated for 2 weeks in a chondrogenic medium, and hypertrophy was induced by withdrawing transforming growth factor , (TGF,), reducing the concentration of dexamethasone, and adding thyroid hormone (T3). Cultures were characterized by histologic, immunohistochemical, and biochemical methods, and gene expression was assessed using quantitative reverse transcription,polymerase chain reaction. Results The combination of TGF, withdrawal, a reduction in the level of dexamethasone, and the addition of T3 was essential for hypertrophy induction. Cytomorphologic changes were accompanied by increased alkaline phosphatase activity, matrix mineralization, and changes in various markers of hypertrophy, including type X collagen, fibroblast growth factor receptors 1,3, parathyroid hormone,related protein receptor, retinoic acid receptor ,, matrix metalloproteinase 13, Indian hedgehog, osteocalcin, and the proapoptotic gene p53. However, hypertrophy was not induced uniformly throughout the pellet culture, and distinct regions of dedifferentiation were observed. Conclusion Chondrogenically differentiating MSCs behave in a manner functionally similar to that of growth plate chondrocytes, expressing a very similar hypertrophic phenotype. Under the in vitro culture conditions used here, MSC-derived chondrocytes underwent a differentiation program analogous to that observed during endochondral embryonic skeletal development, with the potential for terminal differentiation. This culture system is applicable for the screening of hypertrophy-inhibitory conditions and agents that may be useful to enhance MSC performance in cartilage tissue engineering. [source] Carotenoids and retinoids as suppressors on adipocyte differentiation via nuclear receptorsBIOFACTORS, Issue 1-4 2000Teruo Kawada Abstract The adipocyte differentiation program is regulated by the sequential expression of transcriptional activators, mainly peroxisome proliferator activated receptor (PPAR) families. In the present study, we have decided to systematically examine the effects of vitamin A and its precursors, carotenoids and retinoids, on terminal differentiation from preadipocytes to adipocytes on the cellular and molecular aspects. The effects of active form of vitamin A, retinoic acid (RA), are believed to be mediated by specific nuclear receptor proteins [retinoic acid receptor (RAR)] which are members of the steroid and thyroid/retinoid receptor superfamily of ligand dependent transcriptional regulators. RAR,, RAR,, RXR,, and RXR, mRNA were abundant in adipose tissue and 3T3-L1 adipose cells. The autoregulated amplification of RAR, mRNA was observed by these own ligands in 3T3-L1 cells. And, RA inhibited PPAR,2 expression more effectively and caused concomitantly a greater inhibition of adipocyte differentiation. These results suggest that the inhibitory action of adipocyte differentiation by carotenoids and retinoids are exhibited through the RAR up-regulation and the suppression of PPAR,2. The nature of the cross talk of vitamin A actions between the RARs, RXRs and PPARs via co-activator in adipose tissue will likely prove to be important for understanding the process of adipogenesis. [source] The effect of intravesical electrical stimulation on bladder function and synaptic neurotransmission in the rat spinal cord after spinal cord injuryBJU INTERNATIONAL, Issue 8 2009Chang Hee Hong OBJECTIVE To investigate the effects of intravesical electrical stimulation (IVES) on bladder function and synaptic neurotransmission in the lumbosacral spinal cord in the spinalized rat, as the clinical benefits of IVES in patients with increased residual urine or reduced bladder capacity have been reported but studies on the mechanism of IVES have mainly focused on bladder A, afferents in central nervous system-intact rats. MATERIALS AND METHODS In all, 30 female Sprague-Dawley rats were divided equally into three groups: normal control rats, sham-stimulated spinalized rats and IVES-treated spinalized rats. IVES was started 5 weeks after spinal cord injury (SCI) and was performed 20 min a day for 5 consecutive days. At 7 days after IVES, conscious filling cystometry was performed. Sections from the L6 and S1 spinal cord segments were examined for n -methyl- d -aspartic acid receptor 1 (NMDAR1) subunit and ,-aminobutyric acid (GABA) immunoactivity. RESULTS In IVES-treated spinalized rats, the number and maximal pressure of nonvoiding detrusor contractions were significantly less than in sham-stimulated spinalized rats. The mean maximal voiding pressure was also lower in IVES-treated than in sham-stimulated spinalized rats. IVES significantly reduced the interval between voiding contractions compared with the untreated spinalized rats. There was an overall increase in NMDAR1 immunoactivity after SCI, which was significantly lower in IVES-treated spinalized rats. Immunoactivity of GABA after SCI was significantly lower than in the control group and was significantly higher in IVES-treated spinalized rats. CONCLUSION Our results suggest that IVES might affect voiding contractions in addition to inhibiting C-fibre activity and that IVES seems to have a more complex effect on the bladder control pathway. For synaptic neurotransmission in the spinal cord, IVES could possibly shift the balance between excitation and inhibition towards inhibition. [source] Modulation of lung molecular biomarkers by ,-carotene in the Physicians' Health Study,CANCER, Issue 5 2009Chun Liu MD Abstract BACKGROUND: ,-Carotene supplementation showed neither benefit nor harm among apparently healthy physicians (all men) in the Physicians' Health Study (PHS) trial. The objective of the current investigation was to evaluate how long-term ,-carotene supplementation affects molecular markers of lung carcinogenesis in the PHS. METHODS: The protein levels of total p53, cyclin D1, proliferating cellular nuclear antigen (PCNA), retinoic acid receptor , (RAR,), and cytochrome p450 enzyme 1A1 (CYP1A1) were measured using the immunohistochemical method in 40 available archival lung tissue samples from patients who were diagnosed with lung cancer in the PHS. The protein levels of these markers were compared by category of ,-carotene treatment assignment and other characteristics using unconditional logistic regression models. RESULTS: The positivity for total p53, RAR,, cyclin D1, and PCNA was nonsignificantly lower among lung cancer patients who were assigned to receive ,-carotene than those who were assigned to receive ,-carotene placebo. There was a borderline significant difference in CYP1A1 positivity with an OR of 0.2 (95% confidence interval, 0.2-1.1; P = .06) in a comparison of men who received ,-carotene and men who received ,-carotene placebo. CONCLUSIONS: The 50-mg ,-carotene supplementation on alternate days had no significant influence on molecular markers of lung carcinogenesis that were evaluated in the PHS. This finding provides mechanistic support for the main PHS trial results of ,-carotene, which demonstrated no benefit or harm to the risk of developing lung cancer. Cancer 2009. © 2009 American Cancer Society. [source] Effects of retinoids and thiazolidinediones on proliferation, insulin release, insulin mRNA, GLUT 2 transporter protein and mRNA of INS-1 cellsCELL BIOCHEMISTRY AND FUNCTION, Issue 3 2001J. Blumentrath Abstract Both 9-cis-retinoic acid (9cRA) and all-trans-retinoic acid (ATRA) are active metabolites of vitamin A (retinol). There exists an interaction between retinoid receptors and peroxisome proliferator-activated receptors (PPAR,). To define their functions in an insulin secreting system the effects of ATRA, 9cRA and the PPAR, agonist rosiglitazone on cell proliferation, insulin release and glucose transporter (GLUT) 2 of INS-1 cells were tested. Retinoic acid receptor (RAR-, and -,) and retinoid X receptor (RXR-, and -,) proteins are present (immunoblots). Both 9cRA and ATRA inhibit INS-1 cell proliferation ([3H]-thymidine assay) in a concentration dependent manner. Both 9cRA and ATRA increased insulin release, but only ATRA ralsed the GLUT 2 mRNA in a bell-shaped concentration response curve after 48,h. The insulinotropic effect of one compound is not significantly superimposed by the other indicating that the same binding sites are used by 9cRA and ATRA. The acute and chronic effects of the PPAR, agonist rosiglitazone on insulin release were additionally determined since glitazones act as transcription factors together with RXR agonists. At high concentrations (100,,m) rosiglitazone inhibited glucose (8.3,mm) stimulated insulin secretion (acute experiment over 60,min). Insulin secretion, however, was increased during a 24,h treatment at a concentration of 10,,m and again inhibited at 100,,m. Changes in preproinsulin mRNA expression were not observed. Rosiglitazone (100,,m) increased GLUT 2 mRNA paralleled by an increase of GLUT 2 protein, but only after 24,h of treatment. This data indicate that RAR and RXR mediate insulin release. The changes in GLUT 2 have no direct impact on insulin release; the inhibition seen at high concentrations of either compound is possibly the result of the observed inhibition of cell proliferation. Effects of rosiglitazone on preproinsulin mRNA and GLUT 2 (mRNA and protein) do not play a role in modulating insulin secretion. With the presence of an RXR receptor agonist the effect of rosiglitazone on insulin release becomes stimulatory. Thus the effects of RAR-, RXR agonists and rosiglitazone depend on their concentrations, the duration of their presence and are due to specific interactions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Pyrazine Arotinoids with Inverse Agonist Activities on the Retinoid and Rexinoid ReceptorsCHEMBIOCHEM, Issue 7 2009José García Abstract RAR and RXR agonists: A collection of pyrazine-based RAR/RXR ligands were prepared by a series of palladium catalyzed cross-coupling reactions and characterized. Structure,activity relationships were elucidated. Retinoic acid receptor (RAR) ,/,-subtype-selective and retinoid X receptor (RXR) inverse agonist activities are described for pyrazine acrylic acid arotinoid, 14,d. Heterocyclic arotinoids derived from central-region dihalogenated pyrazine scaffolds have been synthesized by consecutive halogen and/or position-selective palladium-catalyzed cross-coupling reactions. Pyrazines were further functionalized as alkyl ethers or methylamines prior to the last Pd-catalyzed reactions. Transient transactivation studies with the retinoic acid receptor (RAR) ,, ,, and , subtypes and with retinoid X receptor (RXR) , revealed distinct agonist, antagonist, and inverse agonist activities for these compounds. Of interest are the RAR,,,-selective inverse agonists with pyrazine acrylic acid structures, in particular 14,c, which is RAR,-selective, and 14,d, a pan-RAR/RXR inverse agonist with more affinity for the RAR subtypes that enhance the interaction of RAR with cognate corepressors. [source] | ||||||||||||||||||||||||||||||||||