tretinoin and diazepinylbenzoic-acid

Active metabolites of vitamin A, retinoic acids (RAs), are known to play critical roles in mucosal immune responses and dramatically inhibit human eosinophil apoptosis, but the detailed mechanisms have not been elucidated. We previously screened for ICAM-1 (CD54) upregulation in RA-stimulated human eosinophils by gene microarray analysis. As ICAM-1 induction and activation were observed to have a role in maintenance of eosinophil survival, we tested the hypothesis that RAs prolong eosinophil survival through ICAM-1 outside-in signaling. Blood-derived isolated eosinophils cultured with 9-cis RA and all-trans RA showed significant upregulation of ICAM-1 mRNA and cell surface expression. TTNPB, a retinoic acid receptor agonist, also induced ICAM-1 expression, while HX630, a retinoid X receptor agonist, did not. Furthermore, an RAR antagonist, HX531, completely inhibited the effect of RAs. Upregulated ICAM-1 was associated with altered kinetics of Akt, ERK, and p38 MAP kinase phosphorylation through ICAM-1 cross-linking, but an ICAM-1-blocking antibody did not affect RA-mediated cell survival. These findings indicate that RAs induce functional ICAM-1 expression through RARs, but the induced ICAM-1 does not contribute to prolongation of eosinophil survival.

Topics: Apoptosis; Benzoates; Biphenyl Compounds; Cell Survival; Cells, Cultured; Eosinophils; Gene Expression; Humans; Intercellular Adhesion Molecule-1; Retinoid X Receptors; Signal Transduction; Tretinoin; Up-Regulation

The electrical activity of neurons is known to play a role in neuronal development, as well as repair of adult nervous tissue. For example, the extension of neurites and motility of growth cones can be modulated by changes in the electrical firing of neurons. The vitamin A metabolite retinoic acid also plays a critical role during nervous system development and is also known to elicit regenerative responses, namely the induction, enhancement, and directionality of neurite outgrowth. However, no studies have previously reported the ability of retinoic acid to modify the electrical activity of neurons. In this study, we determined whether retinoic acid might exert effects on the nervous system by altering the electrical properties of neurons. Using cultured adult neurons from Lymnaea stagnalis, we showed that acute application of retinoic acid can rapidly elicit changes in neuronal firing properties. Retinoic acid caused the presence of atypical firing behavior such as rhythmic bursting and altered the shape of action potentials, causing increases in half-amplitude duration and decay time. Retinoic acid also caused cell silencing, whereby neuronal activity was halted within an hour. These effects of retinoic acid were shown to be both dose and isomer dependent. We then showed that the effects of retinoic acid on cell firing (but not silencing) were significantly reduced in the presence of an retinoid X receptor pan-antagonist HX531. This study suggests that some of the effects of retinoic acid during neuronal development or regeneration might possibly occur as a result of changes in electrical activity of neurons.

Topics: Action Potentials; Animals; Benzoates; Biphenyl Compounds; Cells, Cultured; Isomerism; Lymnaea; Neurons; Retinoid X Receptors; Tretinoin

The molecular basis of CNS myelin regeneration (remyelination) is poorly understood. We generated a comprehensive transcriptional profile of the separate stages of spontaneous remyelination that follow focal demyelination in the rat CNS and found that transcripts that encode the retinoid acid receptor RXR-γ were differentially expressed during remyelination. Cells of the oligodendrocyte lineage expressed RXR-γ in rat tissues that were undergoing remyelination and in active and remyelinated multiple sclerosis lesions. Knockdown of RXR-γ by RNA interference or RXR-specific antagonists severely inhibited oligodendrocyte differentiation in culture. In mice that lacked RXR-γ, adult oligodendrocyte precursor cells efficiently repopulated lesions after demyelination, but showed delayed differentiation into mature oligodendrocytes. Administration of the RXR agonist 9-cis-retinoic acid to demyelinated cerebellar slice cultures and to aged rats after demyelination caused an increase in remyelinated axons. Our results indicate that RXR-γ is a positive regulator of endogenous oligodendrocyte precursor cell differentiation and remyelination and might be a pharmacological target for regenerative therapy in the CNS.

Topics: Aged; Alitretinoin; Animals; Benzoates; Biphenyl Compounds; Cell Differentiation; Cell Lineage; Cells, Cultured; Central Nervous System; Cerebellum; Demyelinating Diseases; Female; Gene Expression Profiling; Humans; Male; Mice; Mice, Knockout; Middle Aged; Multiple Sclerosis; Myelin Sheath; Nerve Regeneration; Neurotoxins; Oligodendroglia; Rats; Rats, Sprague-Dawley; Receptors, Retinoic Acid; Retinoic Acid Receptor gamma; RNA Interference; Stem Cells; Tretinoin

All-trans retinoic acid (ATRA) increases the expression of COX-1 and COX-2 and the production of PGE2, a prostaglandin with anti-inflammatory effects in human mesangial cells (MC). COX-2 increased through a transcriptional mechanism independent of retinoic acid receptors (RAR) and retinoid X receptors (RXR) and dependent on extracellular regulated kinase-1/2 (ERK1/2), that became phosphorylated 5 min after ATRA addition. Here, in rat MC, ATRA also upregulated COX isoenzymes and PGE2 production, but not in the same way as in human MC: (1) PGE2 production increased only slightly; (2) RAR and RXR were involved in the transcriptional upregulation of COX-2 by ATRA since the RAR-pan-antagonist AGN193109 or the RXR-pan-antagonist HX531 abolished the induction of COX-2 mRNA whereas the RAR-pan-agonist TTNPB or the RXR-pan-agonist AGN194204 induced expression of COX-2, and (3) ERK1/2 phosphorylation, though important for COX-2 upregulation, took more than 1 h. Therefore the regulation of COX by ATRA exhibits striking differences between human and rat MC.

Topics: Animals; Benzoates; Biphenyl Compounds; Blotting, Northern; Blotting, Western; Cell Line; Cyclooxygenase 1; Cyclooxygenase 2; Dactinomycin; Dinoprostone; Dose-Response Relationship, Drug; Flavonoids; Humans; Interleukin-1beta; Male; MAP Kinase Kinase 1; Mesangial Cells; Prostaglandin-Endoperoxide Synthases; Protein Synthesis Inhibitors; Quinolines; Rats; Rats, Sprague-Dawley; Retinoid X Receptors; Retinoids; RNA, Messenger; Time Factors; Tretinoin; Up-Regulation

Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a central role in adipocyte and macrophage differentiation. Pioglitazone (Actos, AD4833), an antidiabetic drug, and 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2) have recently been identified as synthetic and natural ligands for PPARgamma, respectively. In this study, we examined the effects of PPARgamma ligands on differentiation and lipogenesis in promyelocytic leukemia NB4 cells, in which PPARgamma protein was expressed and ligand-stimulated PPARgamma-specific transcription of adipocyte fatty-acid binding protein was confirmed. Treatment with PPARgamma ligand (AD4833 or PGJ2) alone markedly suppressed proliferation but did not induce differentiation. The combined treatment of the cells with PPARgamma ligand and all-trans retinoic acid (ATRA) synergistically induced myelocytic differentiation, as determined by nitroblue tetrazolium reducing ability and cell morphology. During these processes of differentiation, we observed marked accumulation of lipid droplets in the cytoplasm. The cellular triacylglycerol levels increased 2.7-fold after treatment with the inducers. Simultaneously, BODIPY-fatty acid was incorporated into the cytosol and concentrated in lipid droplets. The biosynthesis of triacylglycerol-containing BODIPY-fatty acids was increased twofold in differentiated cells. These findings clearly demonstrate that treatment with PPARgamma ligands not only induced differentiation but also stimulated lipogenesis in NB4 cells, indicating a close association between differentiation and lipogenesis in PPARgamma-stimulated human myeloid cells.

Topics: Adipocytes; Anilides; Benzoates; Biphenyl Compounds; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Fatty Acid-Binding Proteins; Humans; Ligands; Lipids; Myeloid Cells; Pioglitazone; PPAR gamma; Prostaglandin D2; Thiazolidinediones; Tretinoin; Triglycerides; Tumor Cells, Cultured; Up-Regulation

HX531 is a retinoid X receptor (RXR) antagonist that inhibits 9-cis retinoic acid-induced neutrophilic differentiation of HL-60 cells. In order to elucidate the inhibitory mechanism of HX531, we have developed a novel ligand sensor assay for RXR in which the receptor-coactivator interaction is directly monitored using surface plasmon resonance (SPR) biosensor technology. A 20-mer peptide from steroid receptor coactivator-1 (SRC-1), containing nuclear receptor interaction motif LXXLL was immobilized on the surface of a BIAcore sensor chip. Injection of human recombinant RXR with or without 9-cis retinoic acid resulted in ligand-dependent interaction with the SRC-1 peptide. Kinetic analysis revealed dissociation constants (KD) of 9-cis RA-preincubated RXR to SRC-1 was 5.92 x 10(-8)M. Using this technique, we found that 1 microM HX531 reduced the ka value of liganded-RXR with SRC-1, suggesting that HX531 reduced the affinity of RXR to SRC-1. This SPR assay system was applied to obtain quantitative kinetic data of RXR ligand binding to the SRC-1 peptide and the alteration of these data by antagonists.

Topics: Alitretinoin; Benzoates; Biphenyl Compounds; CD11b Antigen; Cell Differentiation; Cell Proliferation; Histone Acetyltransferases; Nitroblue Tetrazolium; Nuclear Receptor Coactivator 1; Receptors, Formyl Peptide; Retinoid X Receptors; Surface Plasmon Resonance; Transcription Factors; Tretinoin