Colinearity in the Xenopus laevis Hox-2 complex

We studied the effect of retinoids on the growth and differentiation of a cell line (U 343 MG-A) derived from a human malignant astrocytoma. Cultures treated with all-trans or 13-cis retinoic acid showed a dose-dependent inhibition of proliferation and a marked reduction in the mean cell number at the plateau phase of growth (3.5 x 10(6) vs. 1 x 10(7) cells/25 cm2) compared with untreated cultures. At confluence, cells treated with all-trans or 13-cis retinoic acid were contact-inhibited, whereas control cultures showed crowding, piling, and overgrowth. All-trans retinol or retinyl acetate did not inhibit growth. Astrocytoma cultures treated with all-trans retinoic acid (10(-6) M) for 5 days were modestly growth-inhibited but by day 16 had the same numbers of cells as controls; cultures that received all-trans retinoic acid for 9 days were markedly growth-inhibited for 7 days after the drug was removed. All-trans and 13-cis retinoic acid (10(-6) M) prevented the EDTA-induced cell detachment seen in control cultures. Strongly adherent all-trans retinoic-acid-treated astrocytoma cells grew at a slower rate than did readily detached all-trans retinoic-acid-treated or control cells. Cell spreading, an increased cytoplasmic:nuclear ratio, and greater numbers of broadly bipolar cells, some bearing thin cytoplasmic processes, were seen in cultures treated with 10(-6) M all-trans or 13-cis retinoic acid. Small tightly packed cuboidal cells and large broadly bipolar cells were seen in astrocytoma cultures from which all-trans retinoic acid was removed on days 5 and 9. Indirect immunofluorescence revealed more intense staining with antiserum to glial fibrillary acidic protein in cultures treated with 10(-6) M all-trans retinoic acid than in control cultures; electron-microscope examination of similarly treated cultures revealed more abundant 8-10 nm intermediate filaments than in control cultures. An enzyme-linked immunosorbent assay showed that all-trans or 13-cis retinoic acid caused a dose-dependent increase in the quantity of glial fibrillary acidic protein in the astrocytoma cells.

Homeobox-containing genes may play an important role in establishing embryonic patterns during development of vertebrates. Retinoic acid is able to induce expression of Hox genes in cells in culture and to alter expression patterns in the developing vertebrate embryos. Using wholemount in situ hybridization, we have examined and compared the expression patterns of a homeobox-containing gene, Msx-1, in early normal and vitamin A-deficient quail embryos. At gastrulation stage, Msx-1 is primarily expressed in the posterior half of both normal and vitamin A-deficient embryos. However, the gene is expressed wider and stronger in the vitamin A-deficient embryos. At neurulation stages, Msx-1 is continuously expressed in the posterior region up to Hensen's node and in the edge of the neural fold in both normal and vitamin A-deficient embryos. Notably, in the vitamin A-deficient embryos, Msx-1 is expressed more strongly and is also expressed ectopically in the anterior and precardiac regions. These results provide evidence that endogenous retinoids are involved in the normal expression of Msx-1 in avian embryo and that the expression of Msx-1 is downregulated by endogenous and physiological retinoids in vivo during early avian embryogenesis.

Retinoic acids are morphogenic signaling molecules that are derived from vitamin A and involved in a variety of tissue functions. Two groups of their nuclear receptors have been identified: retinoic acid receptors (RARs) and retinoic acid X receptors (RXRs). All-trans retinoic acid is the high affinity ligand for RARs, and 9-cis retinoic acid also binds to RXRs with high affinity. In cells at high concentrations, all-trans retinoic acid can be converted to 9-cis retinoic acid via unknown mechanisms. It was previously shown that retinoic acids prevents activation-induced death of thymocytes. Here, we report that both all-trans and 9-cis retinoic acid induce apoptosis of mouse thymocytes and purified CD4+CD8+ cells in ex vivo cultures, with 9-cis retinoic acid being 50 times more effective. The induction of apoptosis by retinoic acids is mediated by RARgamma because (a) the phenomenon can be reproduced only by RARgamma-selective retinoic acid analogs, (b) the cell death induced by either retinoic acids or RARgamma analogs can be inhibited by RARgamma-specific antagonists, and (c) CD4+CD8+ thymocytes express RARgamma. In vivo administration of an RARgamma analog resulted in thymus involution with the concomitant activation of the apoptosis-related endonuclease and induction of tissue transglutaminase. The RARgamma pathway of apoptosis is RNA and protein synthesis dependent, affects the CD4+CD8+ double positive thymocytes, and can be inhibited by the addition of either Ca2+ chelators or protease inhibitors. Using various RAR- and RXR-specific analogs and antagonists, it was demonstrated that stimulation of RAR alpha inhibits the RARgamma-specific death pathway (which explains the lack of apoptosis stimulatory effects of all-trans retinoic acid at physiological concentrations) and that costimulation of the RXR receptors (in the case of 9-cis retinoic acid) can neutralize this inhibitory effect. It is suggested that formation of 9-cis retinoic acid may be a critical element in regulating both the positive selection and the "default cell death pathway" of thymocytes.

Naturally occurring retinoids were separated by reversed-phase high-pressure liquid chromatography on an octadecylsilane column eluted with acetonitrile-potassium phosphate buffer (pH 7.2) mixtures. The order of elution from a mixture of 500 ng each of the following standards was 4-oxo retinoic acid (RA), retinyl phosphate (RP), 13-cis RA, all-trans RA, retinol, retinal, retinyl acetate, anhydroretinol, and retinyl palmitate. This method was employed to investigate the cis-trans isomerization of RA and its metabolism in vitamin A-sufficient male rats. Rats (200 g) were injected intraperitoneally with 50 muCi of either [10-3H]-all-trans RA (5.4 micrograms) or [11-3H]-13-cis RA (8.8 micrograms) and killed after 0.5 and 3 hr. Blood, liver, kidney, small intestines, and testes were removed and lyophilized. All-trans RA was converted at 0.5 hr after injection to 13-cis RA in all the tissues examined, with the exception of the small intestine; the conversion ranged from 2.4 to 6.9% of the total radioactivity. In addition, all-trans RA was converted to metabolites (17.5--47.7%) of greater polarity than 4-oxo RA. After 3 hr, most of the radioactivity (75--90%) was found in the highly polar metabolites. 13-cis RA was also partially isomerized to the all-trans RA and to the highly polar metabolites by 0.5 and 3 hr after injection. Appreciable radioactivity (10--41%) still resided in the 13-cis RA fraction after 3 hr. These results indicate that 13-cis RA is partially isomerized to all-trans RA and that all-trans RA is rapidly metabolized to highly polar compounds in tissues of vitamin A-sufficient rats.

Retinoic Acid Receptors Regulate Expression of Retinoic Acid 4-Hydroxylase that Specifically Inactivates All-Trans Retinoic Acid in Human Keratinocyte HaCaT Cells

The binding affinity of retinoic acid receptors (RARs) to their response elements is strongly enhanced in vitro by the formation of heterodimers with retinoid X receptors (RXRs) suggesting that heterodimerization with RXR may be a prerequisite for a RAR-mediated transcriptional response. We found that in Drosophila SL-3 cells that are devoid of endogenous RARs and RXRs the presence of RAR is sufficient to confer a response to all-trans retinoic acid (RA). The transfection of both RAR and RXR and stimulation with their respective ligands all-trans and 9-cis RA leads to a synergistic response. On point mutations of the RAR beta 2 gene promoter RA response element (RARE) the stimulation by RARs showed distinct differences in the absence and presence of RXR. The same differences in transcriptional activity are observed, if mammalian cells containing endogenous RARs and RXRs are stimulated with all-trans RA only or additionally with 9-cis RA. This establishes an RXR-independent and an RXR-dependent pathway of all-trans RA action in Drosophila SL-3 cells as well as in mammalian cells. The presence or absence of 9-cis RA determines by which of the two pathways a response to all-trans RA is mediated.

PML-RARα/RXR Alters the Epigenetic Landscape in Acute Promyelocytic Leukemia

Sir: We report a case of acute respiratory distress syndrome occurring during a treatment by all-trans retinoic acid. A 46-yearold non-smoking female presented with acute promyelocytic leukemia with classic translocation. The treatment began with all-trans retinoic acid orally at a daily dose of 45 mg/m2 body surface area. On day 16 after starting this treatment, she developed fever (39 °C), tachycardia (125 bpm), and dyspnea (respiratory rate: 28/min). Because of these symptoms, she was admitted to the Intensive Care Unit (ICU). A chest X-ray showed bilateral diffuse interstitial infiltrates without pleural effusion. An echocardiography revealed good left ventricular function without pericardial effusion. In order to diagnose infectious pneumonia, we performed a bronchoalveolar lavage (BAL) and empiric antimicrobial treatment was first begun with a combination of piperillin+tazobactam and vancomycin. All microbial samples failed to reveal the growth of pathogenic microorganisms. Histologic BAL fluid examination revealed an increased mature myeloid cells count with 60 % neutrophils and 5 % eosinophils. The blood leukocytes count had increased from 3.9 to 11 g/1. Blood gas analysis, with oxygen flow of 12 1/min, showed a PaO 2 of 59 mmHg. Four days later, her respiratory function deteriorated and required intermittent non-invasive ventilation with continuous positive airway pressure (8 cmH20 and FIO2:80 %). Alltrans retinoic acid was discontinued and she was treated with dexamethasone 10 mg intravenously every 12 h for six doses. Ten days later, all symptoms had disappeared and physical readings were normal. The use of all-trans retinoic acid induces hematologic remission in patients with acute promyelocytic leukemia [1]. The first complications of this treatment were reported by Huang and Castaigne [2, 3]. The retinoic acid syndrome involves hyperleukocytosis, fever, respiratory distress, pleural and pericardial effusion and hypotension occurring 2-21 days after the start of treatment with all-trans retinoic acid [4]. In our case, the symptoms were initially attributed to infectious pneumonia, because all the signs of retinoic acid syndrome were not present. Congestive heart failure did not seem likely since electrocardiograms and echocardiographs showed non-specific changes. After 4 days of ineffectiveness of the antibiotic therapy, we decided to begin corticosteroid treatment. Indeed, firstly, quantitative viral, bacterial and fungaI BAL fluid cultures revealed no growth; secondly, the histologic BAL fluid examination was compatible with retinoic acid syndrome and, thirdly, acute lung injury worsened, requiring non-invasive ventilation. Acute lung injury appears between 2-21 days of treatment with all-trans retinoic acid [5]. The diagnosis was difficult to establish because our patient developed respiratory failure only (neither shock nor renal failure). Even with sterile bacterial cultures, the diagnosis of infectious pneumonia is never completely excluded in cases of immunocompromised patients. In all reported cases, the symptoms were associated with a rising leucocyte count. The peak of the leucocyte count was not necessarily very high. The onset of respiratory distress was not associated with leukocytosis. Acute lung injury was almost certainly due to the increased migration of cells into the lung tissues. Retinoic acid upregulates genes that encode leukocyte adhesion receptors [6]. In this way, retinoic acid increases leukocyte adherence to capillary endothelial cells. This would explain the increased count of myeloid cells found in the BAL fluid. All-trans retinoic acid could increase integrin expression on the leukemic cell surface, which would enhance the cell's adherence to capillary endothelium. Dexamethasone would block the capillaryleak syndrome, inhibit the generation of nitric oxide and secretion of pro-inflammatory cytokines. It is important to recognise this syndrome because intervention with dexamethasone may be life-saving.

Regulation of tissue homeostasis is crucial to disease prevention; cell division, cell cycle arrest, differentiation and apoptosis have to be tightly controlled in order to maintain this homeostasis. Retinoic acid (RA) and the histone deacetylase inhibitors (HDACIs) have profound effects on these processes and thus may be critical regulators of homeostasis. Consequently, RA and/or histone deacetylase inhibitors are currently being tested in clinical trials for a variety of cancers. Unfortunately, little is known of the Regulation of tissue homeostasis is crucial to disease prevention; cell division, cell cycle arrest, differentiation and apoptosis have to be tightly controlled in order to maintain this homeostasis. Retinoic acid (RA) and the histone deacetylase inhibitors (HDACIs) have profound effects on these processes and thus may be critical regulators of homeostasis. Consequently, RA and/or histone deacetylase inhibitors are currently being tested in clinical trials for a variety of cancers. Unfortunately, little is known of the overall affect of these compounds on cellular gene expression. Therefore, we decided to compare the effects of all-trans retinoic acid (ATRA) and a particular HDACI – Trichostatin A (TSA) - on an embryonal carcinoma (EC) cell line (F9) using gene chip analysis. We have focused particular attention on those genes that may be differentially affected by these compounds. Within the parameters established for this study, only 116 of the 12,488 genes examined were similarly regulated by ATRA and TSA: 75 positively and 41 negatively. An additional 70 genes were affected by only one of the compounds and 19 genes were actually inversely regulated. The gene set inversely regulated by ATRA and TSA includes several important patterning genes as well as the crucial tumor suppressor/promoter, transforming growth factor beta 1 (TGF?1). Promoter analysis suggests a motif that may regulate one set of these genes. This study provides the first comprehensive comparison of global gene expression on EC cells as affected by ATRA and a HDAC inhibitor (TSA); reveals new targets for ATRA and HDAC inhibitors; identifies a new regulatory motif; demonstrates that ATRA and HDAC inhibitors do not always act synergistically on gene expression; and examines particular questions regarding their concurrent clinical application.ral important patterning genes as well as the crucial tumor suppressor/promoter, transforming growth factor beta 1 (TGF?1). Promoter analysis suggests a motif that may regulate one set of these genes. This study provides the first comprehensive comparison of global gene expression on EC cells as affected by ATRA and a HDAC inhibitor (TSA); reveals new targets for ATRA and HDAC inhibitors; identifies a new regulatory motif; demonstrates that ATRA and HDAC inhibitors do not always act synergistically on gene expression; and examines particular questions regarding their concurrent clinical application.

We investigated the effect of two isomers of retinoic acid (RA), all-trans RA and 9-cis RA, on the proliferation of Y79 human retinoblastoma cells. The two isomers inhibited the cell proliferation in a concentration-dependent manner. The IC50 for this inhibition by all-trans RA and 9-cis RA was 1.50 and 0.15 microM, respectively. The inhibitory effect of 9-cis RA on Y79 cell growth was observed within 24 hr, thereafter the cell number was gradually decreased. In contrast, no inhibition by all-trans RA of Y79 cell growth was observed within 24 hr, thereafter the cell number was slightly increased. In these cases, the cell viability at 4 days after the addition of 9-cis RA and all-trans RA was more than 90% and 95%, respectively. These results indicate that the two RA inhibit the proliferation of Y79 human retinoblastoma cells without inducing the cell death and that the effect of 9-cis RA on the inhibition of Y79 cell growth is much greater than that of all-trans RA.

PurposeAll-trans retinoic acid (ATRA) plays an important role in ocular development. Previous studies found that retinoic acid could influence the metabolism of scleral remodeling by promoting retinal pigment epithelium (RPE) cells to secrete secondary signaling factors. The purpose of this study was to investigate whether retinoic acid affected secretion of bone morphogenetic protein 2 (BMP-2) and matrix metalloproteinase 2 (MMP-2) and to explore the signaling pathway of retinoic acid in cultured acute retinal pigment epithelial 19 (ARPE-19) cells.MethodsThe effects of ATRA (concentrations from 10−9 to 10−5 mol/l) on the expression of retinoic acid receptors (RARs) in ARPE-19 cells were examined at the mRNA and protein levels using reverse transcription-polymerase chain reaction (RT-PCR) and western blot assay, respectively. The effects of treating ARPE-19 cells with ATRA concentrations ranging from 10−9 to 10−5 mol/l for 24 h and 48 h or with 10-6mol/l ATRA at different times ranging from 6h to 72h were assessed using real-time quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA). The contribution of RARβ-induced activation of ARPE-19 cells was confirmed using LE135, an antagonist of RARβ.ResultsRARβ mRNA levels significantly increased in the ARPE-19 cells treated with ATRA for 24h and 48h. These increases in RARβ mRNA levels were dose dependent (at concentrations of 10−9 to 10−5 mol/l) with a maximum effect observed at 10−6 mol/l. There were no significant changes in the mRNA levels of RARα and RARγ. Western blot assay revealed that RARβ protein levels were increased significantly in a time-dependent manner in ARPE-19 cells treated with 10−6 mol/l ATRA from 12 h to 72 h, with a marked increase observed at 24 h and 48 h. The upregulation of RARβ and the ATRA-induced secretion in ARPE-19 cells could be inhibited by the RARβ antagonist LE135.ConclusionATRA induced upregulation of RARβ in ARPE-19 cells and stimulated these cells to secrete BMP-2 and MMP-2.

Background The improvement of in vitro maturation (IVM) protocols through the supplementation with different molecules has become an alternative to increase the culture medium efficiency. Tretinoin (TTN, all-trans retinoic acid, ATRA), is an active metabolite of vitamin A [1], that mediates cell proliferation, cell differentiation, and embryonic development process. In in vitro production embryos systems, TTN acts improving cytoplasmic maturation process in oocytes, developmental competence in early embryos, and quality in blastocysts [2]. Studies have been demonstrated the presence of a, b and g subtypes of retinoic acid receptors (RARa, RARb, RARg) for TTN in oocyte, hatched blastocysts, and cumulus cells [3]. This molecule can also be used for treatment of skin disorders and for anti-tumor treatment, so researchers have been associated TTN with polymeric nanoparticles to protect it from degradation and to improve its chemical stability and efficacy [4]. The aim of present study was to test the concentrationdependent effect of supplementation of free tretinoin (TTN) and tretinoin-loaded lipid-core nanocapsules (TTN-LNC) in bovine in vitro maturation media, and its influence in reactive oxygen species (ROS) production in two-to four-cell stage embryos. In conclusion, tretinoinloaded lipid-core nanocapsules added in in vitro maturation media highly protects embryos at early stage of development against oxidative stress. Methods The experimental groups were established, and cumulus-oocyte complexes (COCs) were matured in oocyte in vitro maturation medium supplemented with 0.25, 0.5 and 1 μM of TTN-LNC or TTN. Control groups of COCs matured without treatment and treated only with blank lipid-core-nanocapsules (LNC) were also examined. The oocytes were in vitro fertilized in order to evaluate the ROS levels in embryos produced by the different treatments. The ROS formation was evaluated in two-to four-cell stage embryos as previously described [5] with some modifications.

Anti-Leukemic Effect of Retinoic Acid in Non-APL AML Cells

While it is known that Retinoic Acid (RA) induces meiosis in mouse female fetal gonads, the mechanisms which regulate this process during spermatogenesis are poorly understood. We show that the All trans RA derivative (ATRA) and Kit Ligand (KL) increase meiotic entry of postnatal mouse spermatogonia in vitro without synergism. Competence to enter meiosis is reached by spermatogonia only at the stage in which they undergo Kit-dependent divisions. Besides increasing Kit expression in spermatogonia, ATRA also upregulates KL expression in Sertoli cells. Both ATRA and KL increase the expression of Stimulated by Retinoic Acid Gene 8 and Dmc1, an early meiotic marker. A specific Kit tyrosine kinase inhibitor prevents the increase in the number of meiotic cells induced by both the two factors, suggesting that they converge on common Kit-dependent signalling pathways. Meiotic entry induced by ATRA and KL is independent from their ability to affect germ cell viability, and is mediated by the activation of PI3K and MAPK pathways through Kit autophosphorylation. ATRA-induced phosphorylation of the two downstream kinases is mediated by a non-genomic mechanism.These data suggest that RA may control the timing of meiosis by influencing both the somatic and the germ cell compartment of the postnatal testis through the activation of the KL/Kit system.

Fatty Acid Binding Protein FABP5 Inhibition Activates Retinoic Acid Signaling and Induces Differentiation in Acute Myeloid Leukemia