13-cis-retinoic Acid Research Articles

VITAMIN A, RETINOIC ACID AND TAMIBAROTENE, A FRONT TOWARD ITS ADVANCES: A REVIEW

Vitamin A and its derivative retinoic acid (13-cis RA, 9-cis RA, all-trans RA) and recent tamibarotene have been shown a broad variety of biological actives in human, such as vision, embryonic development, cell growth and cellular differentiation and immune function. These precise functions of RA are mediated by their retinoic acid receptors (RARs). In the past five decades, retinoic acid (RA) proved therapeutic benefits in cancer prevention, in skin diseases and in acute promyelocytic leukemia (APL).The elucidation of the molecular basis of vitamin A acid and its retinoid pharmacology in APL has been illustrated in several publications, the detail molecular model of gene regulation had also been proposed by Zhu in earlier 90s. A molecular model is further revised. As an approach to APL treatment, one possible the action of retinoic acid (RA), A consensus sequence (TCAGGTCA motif ) has been postulated for thyroid hormone (TRE) and retinoic acid responsive element (RARE)-containing in the promoter region of target genes. High dose of RA-RARE-PML/RARa complexes in intracellular localization appears to relieve repressors from DNA-bound receptor, including the dissociation of co-re pressor complexes N-CoR, SMRT and HDACs from PML-RARa or PML-RARa/RXR. Also release PML/RARa -mediated transcription repression. This transcriptional derepression occurs at RARa target gene promoter. Consequentially, PML-RARa chimera converted receptor from a repressor to a RA-dependent activator of transcription. The resulting pml-RARA oncoprotein proteolytic degradation occurs through the autophagy-lysosome pathway and the ubiquitin SUMO-proteasome system(UPS) as well as caspase 3, or lysosomal protease (cathepsin D) enzyme or/and EI-like ubiquitin-activating enzyme(UBEIL) induction. Accordingly the expression level of PML-RARa downregulated. PML protein relocalizes into the wild-type nuclear body (PML-NB) configuration or a truncated PML-RARa fusion fragment detected or/and the wild-type RAR upregulated. An effect is to relieve the blockade of pml/RARa-mediated RA dependent promyelocytic differentiation, and retinoic acid (9-cid RA,ATRA, Am80) in APL therapy. Here, oncogenic pml/RARa as constitutive transcriptional repressor that block myeloid differentiation at promyelocytic phenotype. RA can overcome the transcrptional repressor activity of pml/RARa. The oncogenic pml/RARa uncovers a pathogenic role in leukemogenesis of APL through blocking promyelocytic differentiation. This oncogenic receptor derivative pml/ RARa chimera is locked in their "off" regular mode thereby constitutively repressing transcription of target genes or key enzymes (such as AP-1, PTEN, DAPK2,UP.1, p21WAF/CCKN1A）that are critical for differentiation of hematopoietic cells. This is first described in eukaryotes.

A retinoid X receptor partial agonist attenuates pulmonary emphysema and airway inflammation

BackgroundRetinoid X receptors (RXRs) are members of the nuclear receptor (NR) superfamily that mediate signalling by 9-cis retinoic acid, a vitamin A derivative. RXRs play key roles not only as homodimers but also as heterodimeric partners, e.g., for retinoic acid receptors, vitamin D receptors, and peroxisome proliferator-activated receptors. The NR family may also play important roles in the development of emphysema. However, the role of RXRs in the pathogenesis of emphysema is not well defined.MethodsWe developed a novel RXR partial agonist (NEt-4IB) and investigated its effect and mechanism compared to a full agonist (bexarotene) in a murine model of emphysema. For emphysema induction, BALB/c mice received intraperitoneal cigarette smoke extract (CSE) or intratracheal porcine pancreas elastase (PPE). Treatment with RXR agonists was initiated before or after emphysema induction.ResultsTreatment with NEt-4IB significantly suppressed the increase in static lung compliance and emphysematous changes in CSE-induced emphysema and PPE-induced established and progressive emphysema. NEt-4IB significantly suppressed PPE-induced neutrophilic airway inflammation and the levels of keratinocyte chemoattractant (KC), C-X-C motif ligand5 (CXCL5), interferon (IFN)-γ and IL-17. NEt-4IB also improved the matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance and the reduced anti-oxidant activity in bronchoalveolar lavage (BAL) fluid. NEt-4IB suppressed PPE-induced vascular endothelial growth factor (VEGF) expression in the airway. Treatment with NEt-4IB and bexarotene significantly suppressed the increase in static lung compliance and emphysematous changes. However, adverse effects of RXR agonists, including hypertriglyceridemia and hepatomegaly, were observed in bexarotene-treated mice but not in NEt-4IB-treated mice.ConclusionThese data suggest that RXRs play crucial roles in emphysema and airway inflammation, and novel partial RXR agonists could be potential therapeutic strategies for the treatment of PPE- and CSE-induced emphysema.

Efficacy and safety of oral alitretinoin as treatment for chronic hand eczema in France: a real-life open-label study.

Chronic hand eczema is an inflammatory dermatosis that results in a significant psychological and socio-economic burden. Alitretinoin (AL) is indicated in adults with severe chronic hand eczema (sCHE) unresponsive to potent topical corticosteroids. To assess AL effectiveness and safety in patients with sCHE under real-life conditions based on a prospective observational study in France (2010-2014). Clinical severity was assessed using Physician Global Assessment (PGA) and Modified Total Lesion Symptom Score (mTLSS) and quality of life by Skindex and visual analogue scales. Patients were treated with AL for 12-24 weeks and followed for 24 months. Responders were patients with clear/almost clear skin based on PGA at the end of treatment and the primary outcome was remission (clear, almost clear, or mild skin) at one and two years after treatment. A total of 394 patients with severe or moderate PGA were included in the study by 109 dermatologists. AL treatment duration was 5.4 ± 4.1 months (mean ± SD) and 112/274 patients evaluated at the end of treatment were responders. Of the 112 responders, 41/51 evaluable patients were in remission after one year and 36/46 after two years. At the end of treatment, Skindex improved from 48.8 ± 18.1% to 27.1 ± 23.2%. Among the 112 responders, 68/84 did not relapse (mTLSS increased >75% from baseline). The most common adverse events were headache (24%) and dyslipidaemia (4%). This study supports a positive benefit/risk profile for AL for sCHE patients unresponsive to topical corticosteroids.

Nuclear receptor ligands induce TREM-1 expression on dendritic cells: analysis of their role in tumors

ABSTRACTDendritic cells (DCs) initiate adaptive immune responses after their migration to secondary lymphoid organs. The LXR ligands/oxysterols and the RXR ligand 9-cis Retinoic Acid (9-cis RA) were shown to dampen DC migration to lymphoid organs through the inhibition of CCR7 expression. We performed transcriptomics of DCs undergoing maturation in the presence of the LXR ligand 22R-Hydroxycholesterol (22R-HC). The analysis highlighted more than 1500 genes modulated by 22R-HC treatment, including the triggering receptor expressed on myeloid cells (TREM)-1, which was found markedly up-regulated. We tested the effect of other nuclear receptor ligands (NRL) and we reported the induction of TREM-1 following RXR, RAR and VDR activation. From a functional point of view, triggering of TREM-1 induced by retinoids increased TNFα and IL-1β release, suggesting an active role of NRL-activated TREM-1+ DCs in inflammation-driven diseases, including cancer. Consistently with this hypothesis we detected DCs expressing TREM-1 in pleural effusions and ascites of cancer patients, an observation validated by the induction of TREM-1, LXR and RAR target genes when monocyte-DCs were activated in the presence of tumor-conditioned fluids. Finally, we observed a better control of LLC tumor growth in Trem-1−/- bone marrow chimera mice as compared to wild type chimera mice. Future studies will be necessary to shed light on the mechanism of TREM-1 induction by distinct NRL, and to characterize the role of TREM-1+ DCs in tumor growth.

Aging and retinoid X receptor agonists on masculinization of female Pomacea canaliculata, with a critical appraisal of imposex evaluation in the Ampullariidae

Ampullariidae are unique among gastropods in that females normally show a primordium of the copulatory apparatus (CApp). The aims of this study were (a) to quantitatively evaluate the development and growth of the female CApp with age; (b) to compare the effects of RXR and PPARγ agonists in adult females of known age and (c) to explore the effect of masculinizing RXR agonists on the expression of RXR in the CApp. It was found that the CApp grows and develops with age. A significant increase in penile sheath length (PsL) and also in a developmental index (DI) was observed in 7–8 months old females, as compared with 4–5 months old ones. A reported endogenous agonist of RXR, 9-cis retinoic acid (9cis-RA), as well as two organotin compounds, tributyltin (TBT) and triphenyltin (TPT) which have been also reported to bind to RXR, were injected and its masculinizing effects were measured. Also, the effect of a PPARγ agonist, rosiglitazone, was studied. All studied RXR agonists, but not the PPARγ agonist, were effective in increasing PsL, penile length (PL) and DI. Finally, the expression of the RXR in the CApp was studied (Western blot) in control, TBT, TPT, and 9cis-RA treated females. A significantly increased expression of RXR was only observed after 9cis-RA treatment. It is concluded that (a) development and growth of the CApp is significantly affected by female age; (b) reported RXR agonists, but not a PPARγ agonist, cause female masculinization of young females. An appraisal of previous studies of female masculinization in the Ampullariidae has also been made and it is emphasized that the masculinizing effect of aging should be considered, particularly when interpreting field data.

Effects of oral isotretinoin therapy on the nasal cavities

IntroductionIsotretinoin (13 cis-retinoic acid) is the most effective treatment for acne vulgaris and is the only treatment option that can provide either remission or a permanent cure. ObjectiveThe aim of this study was to use both subjective and objective methods to assess the nasal complaints of patients with severe acne who received oral isotretinoin therapy. MethodsFifty-four subjects were enrolled in the study. All the subjects were assessed with subjective (NOSE and VAS questionnaires) and objective (rhinomanometry and saccharine) tests to determine the severity of their nasal complaints. ResultsThe mean severity scores (min: 0; max: 100) for nasal dryness/crusting and epistaxis were 0.47±1.48 (0–5); 0.35±1.30 (0–5) at admission, 3.57±4.45 (0–10); 2.26±4.71 (0–20) at the first month, and 4.28±6 (0–20); 2.26±4.71 (0–20) at the third month of the treatment respectively. Total nasal resistance of 0.195±0.079 (0.12–0.56)Pa/cm3/s at admission, 0.21±0.084 (0.12–0.54)Pa/cm3/s at the first month, and 0.216±0.081 (0.14–0.54)Pa/cm3/s at the third month. ConclusionOral isotretinoin therapy can cause the complaint of nasal obstruction. In addition, nasal complaints, such as dryness/crusting and epistaxis, significantly increase in patients during the therapy schedule.

An evaluation of peripapillar choroidal thickness in patients receiving systemic isotretinoin treatment

Purpose Oral isotretinoin (13-cis retinoic acid, 13-cis RA) was approved for severe acne treatment by the FDA in 1982. The ocular side effects associated with oral isotretinoin use are mostly dose-dependent. Numerous ocular pathologies affect peripapillary choroidal layer primarily or indirectly. Objective Evaluation of the peripapillary choroidal layer in the patients receiving oral isotretinoin therapy may aid in explaining the pathophysiology of ocular side effects. Methods In this study, peripapillary choroidal thickness was assessed in the patients receiving oral isotretinoin treatment via optical coherent tomography technique. Results Significant difference was found in the superotemporal and temporal areas. Conclusion Oral isotretinoin treatment may affect the thickness of the peripapillary choroidal layer.

Biochemical Effects of Retinoid Derivatives on Mesenchymal Stem Cells In Vitro

The studies we performed targeted the effects of all-trans retinol (vitamin A) and some retinoid derivatives (including tretinoin or all-trans retinoic acid, retinyl propionate, 9-cis retinoic acid, 13-cis retinoic acid), as well as of tazarotenic acid on apoptosis of rat mesenchymal stem cells, cultured after isolation. Tazarotenic acid is considered to be relatively selective and a potent agonist for RARb and RARg and less for RARa. The same time, tazarotenic acid is not binding to RXRs (retinoid X receptors). The relevant analysis of our experimental results demonstrated that 13-cis retinoic acid was the most potent inducer of apoptosis of cultured mesenchymal stem cells of rat origin when compared to other retinoid derivatives, as follows: 13-cis retinoic acid ] 9-cis retinoic acid ] tazarotenic acid ] all-trans retinoic acid ] retinyl propionate ] retinol (or vitamin A). Very interesting and unexpected were the apoptotic effects of 1 �M tazarotenic acid for 24 hours in our experiments, very close to those induced by all-trans retinoic acid (tretinoin). The apoptosis induced by 13-cis retinoic acid, a principal activator of RARb and RARg, and that induced by 9-cis retinoic acid, a major activator of RXRs, suggests different pathways activated by these retinoid derivatives.

DHA upregulates FADS2 expression in primary cortical astrocytes exposed to vitamin A.

The fads2 gene encoding delta6-desaturase, the rate-limiting enzyme of the LCPUFA biosynthesis is expressed in astrocytes. Dietary fatty acids, which cross the blood-brain barrier, may regulate the transcription of lipogenic enzymes through activation of transcription factors such as peroxisome proliferator-activated receptors (PPARs). The PPARs form the transcription complex with retinoid X receptors (RXRs) that are activated by 9-cis retinoic acid, a metabolite of vitamin A (VA). The study examines whether challenge of astrocytes with VA, prior 24-h treatment with palmitic acid (PA), alpha-linolenic acid (ALA) or docosahexaenoic acid (DHA) has the effect on the FADS2 expression. RT-qPCR showed that in astrocytes not challenged with VA, PA increased fads2 gene expression and DHA decreased it. However, in VA-primed astrocytes, PA doubled the FADS2 mRNA levels, while DHA increased fads2 gene expression, oppositely to non-primed cells. Furthermore, similar changes were seen in VA-primed astrocytes with regard to delta6-desaturase protein levels following PA and DHA treatment. ALA did not have any effect on the FADS2 mRNA and protein levels in either VA-primed or non-primed astrocytes. These findings indicate that in the presence of vitamin A, DHA upregulates fads2 gene expression in astrocytes.

PO-215 Resistance to retinoids – analysis of putative biomarkers in neuroblastoma cells and tumour tissue samples

IntroductionRetinoids represent a popular group of differentiation inducers that are successfully used in oncology for treatment of neuroblastoma (NBL) in children. However. differentiation therapy has some limitations including toxicity and intrinsic or acquired resistance to retinoids observed in many patients. Therefore, seeking for molecular markers able to predict therapeutic response to retinoid administration is undoubtedly an important aspect of their use in clinical practice. Several putative biomarkers indicating sensitivity or resistance of NBL cells to retinoids were reported in recent studies. The main aim of our study was to analyse the expression of five candidate proteins (PBX1, HOXC9, HMGA1, HMGA2 and DDX39A) in one experimental cohort (NBL cell lines; relevant FFPE tumour samples).Material and methodsIn this study, 20 patient-derived NBL cell lines were used for the experiments. Sensitivity or resistance to natural (all-trans retinoic acid, 13-cis retinoic acid, 9-cis retinoic acid) and synthetic (fenretinide, bexarotene) retinoids was determined by MTT assay. Endogenous expression of the candidate biomarkers was analysed both on mRNA (RT-PCR) and protein (immunoblotting) levels in cell lines and on protein level (immunohistochemistry) in FFPE tumour samples. Changes in expression of these markers after treatment with retinoids were also analysed.Results and discussionsNBL cell lines resistant to retinoids showed either presence of HMGA2 or increased expression of HMGA1 together with PBX1. Cell lines without a detectable expression of HOXC9 is on both mRNA and protein level are resistant to retinoids. Increase of expression of HOXC9 protein after retinoid treatment was detected in sensitive cell lines only. Very strong expression of PBX1 protein was found in tumour samples taken from patients showing resistance or poor clinical outcome after treatment with retinoids.ConclusionOur experimental study confirmed the usefulness of selected putative markers indicating sensitivity or resistance of NBL cells to retinoids in one experimental cohort consisting of patient-derived cell lines and respective tumour samples.This study was supported by the project AZV MZCR 15-34621A.

Abstract 3739: Nuclear hormone receptors modulate imatinib resistance in chronic myeloid leukemia (CML)

Abstract Despite the impressive success of molecular targeted therapy in chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKI) such as imatinib (IM), a proportion of patients exhibit suboptimal response and intolerance to the drug. While the mechanism by which resistance or intolerance develops is not completely clear, it is possible that several secondary modifiers could determine disease progression and drug response in CML. Nuclear Hormone Receptors-NHRs are attractive but less explored therapeutic targets in myeloid leukemia. The impressive success of treatment with ATRA, a RAR ligand, in the treatment of APL has not been translated to other myeloid leukemia subtypes. Recently, Prost et al., 2015 showed that Peroxisome proliferator-activated receptor-γ agonist Pioglitazone eliminates the residual CML stem cell pool and these patients remained in complete molecular response even after withdrawal of IM. The role of other NHRs in CML TKI resistance has not been explored extensively. Based on the in-vitro drug sensitivity data, CML cell lines KU812, EM2 were grouped as sensitive (IC50-0.15 & 2.29uM) and Lama84, KCL22 were grouped as resistant (IC50-54.45 & 66uM) to IM. The NHRs and coregulators that are differentially expressed between IM sensitive and resistant cell lines were identified using NHR RT2 PCR profiler array (SAbiosciences). Based on +2 fold cutoff, the differentially expressed NHRs between test and control group were identified. Eight NHRs (AHR, AR, ESR1, ESRRG, PPARγ, RXRA, RXRB & THRA) were upregulated in the sensitive compared to the resistant cell lines, which was further validated by qRT-PCR. To understand the effect of these NHRs in sensitizing resistant CML cells to Imatinib, KCL22 and Lama84 cells were pretreated with NHR ligands, followed by increasing concentrations of Imatinib (5µM-100µM). Ligands of RXR (9-cis retinoic acid), AR (testosterone) and ESRRG1 (GSK4716) significantly improved IM sensitivity by increasing the RNA expression of IM influx transporter hOCT1, which was also reported by Wang et al., 2012; Austin et al., 2014 using ligands for RXR, PXR and PPARγ. Pretreatment with these ligands did not have significant effect on the mRNA expression of BCR-ABL, but there was increased inhibition of the BCR-ABL downstream targets such as pCRKL, pSTAT5 and pAKT at the protein level in combination with IM. The AR, RXR & ESRRG ligands significantly decreased the IC50 to IM (p<0.0001) in primary CML cells (n=22) in combination with IM. We also observed significant sensitization of primary samples (n=7) to IM when used in combination with clinically available RXR and AR ligands isotretinoin (p=0.0011) & stanozolol (p=0.0054). Our finding suggests that NHR ligands, especially RXR, AR & ESRRG when used in combination with IM could overcome resistance. Further studies are warranted to confirm the mechanistic effects of these ligands in modulating drug resistance in CML. Citation Format: Bharathi M. Rajamani, Sreeja Karathedath, Raveen Stephen Illangeswaran, Esther Sathya Bama Benjamin, Vikram Mathews, Aby Abraham, Poonkuzhali Balasubramanian. Nuclear hormone receptors modulate imatinib resistance in chronic myeloid leukemia (CML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3739.

ECPIRM, a Potential Therapeutic Agent for Cutaneous T-Cell Lymphoma, Inhibits Cell Proliferation and Promotes Apoptosis via a JAK/STAT Pathway.

Retinoids are important agents for the treatment of cutaneous T-cell lymphomas (CTCL). But side effects and drug resistance caused by activation of RAR/RXR limited their clinical application. Therefore, it is urgent to develop new agents to fight against CTCL. ECPIRM, a 13-cis retinoic acid derivative, was reported that it inhibited proliferation and induced apoptosis of SCL-1 cells. The aim of this study was to evaluate the biological activities and mechanisms of ECPIEM. The effect of ECPIRM on cell proliferation was determined by MTT assay and Trypan blue exclusion assay while FACS analysis was used to detect changes in cell cycle and apoptosis in HUT78 cells. The influence of ECPIRM on RAR/RXR and JAK/STAT signaling was evaluated by western blot analysis. ECPIRM, better than other agents (all-trans retinoic acid,13-cis-retinoic acid or bexarotene), inhibited proliferation and induced apoptosis significantly in HUT78 cells, but with little cytotoxicity on normal lymphocytes. Then ECPIRM induced G0/G1 phase arrest by decreasing the expression of cyclinD1, cyclinE, CDK2 and CDK4 while increasing p21. Furthermore, the unaffected expression of RAR and RXR members suggested that ECPIRM acted independently of RAR/RXR pathway in HUT78 cells. But decreased phosphorylation of JAK1, STAT3, STAT5 and downregulated Bcl-xL, Cyclin D1 and c-Myc indicated that ECPIRM inhibited the activation of JAK/STAT signaling. ECPIRM inhibited proliferation, induced apoptosis and G0/G1 phase arrest in HUT78 cells through inhibiting JAK/STAT pathway but not RAR/RXR pathway, which presented ECPIRM as a promising candidate for the treatment of CTCL patients.

Maintenance immunotherapy in patients with metastatic breast cancer (MBC) who have a clinical benefit with chemotherapy. Long-term follow-up of a phase II study.

e13068Background: In a phase I study we have shown, that a combination of 13-cis retinoic acid (RA) and interleukin-2 (IL-2) was feasible and was able to improve the immune function of cancer patie...

The vitamin D hormone and its nuclear receptor: molecular actions and disease states.

Vitamin D plays a major role in bone mineral homeostasis by promoting the transport of calcium and phosphate to ensure that the blood levels of these ions are sufficient for the normal mineralization of type I collagen matrix in the skeleton. In contrast to classic vitamin D-deficiency rickets, a number of vitamin D-resistant rachitic syndromes are caused by acquired and hereditary defects in the metabolic activation of the vitamin to its hormonal form, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), or in the subsequent functions of the hormone in target cells. The actions of 1,25(OH)2D3 are mediated by the nuclear vitamin D receptor (VDR), a phosphoprotein which binds the hormone with-high affinity and regulates the expression of genes via zinc finger-mediated DNA binding and protein-protein interactions. In hereditary hypocalcemic vitamin D-resistant rickets (HVDRR), natural mutations in human VDR that confer patients with tissue insensitivity to 1,25(OH)2D3 are particularly instructive in revealing VDR structure function relationships. These mutations fall into three categories: (i) DNA binding/nuclear localization, (ii) hormone binding and (iii) heterodimerization with retinoid X receptors (RXRs). That all three classes of VDR mutations generate the HVDRR phenotype is consistent with a basic model of the active receptor as a DNA-bound, 1,25(OH)2D3-liganded heterodimer of VDR and RXR. Vitamin D responsive elements (VDREs) consisting of direct hexanucleotide repeats with a spacer of three nucleotides have been identified in the promoter regions of positively controlled genes expressed in bone, such as osteocalcin, osteopontin, beta 3-integrin and vitamin D 24-OHase. The 1,25(OH)2D3 ligand promotes VDR-RXR heterodimerization and specific, high affinity VDRE binding, whereas the ligand for RXR, 9-cis retinoic acid (9-cis RA), is capable of suppressing 1,25(OH)2D3-stimulated transcription by diverting RXR to form homodimers. However, initial 1,25(OH)2D3 liganding of a VDR monomer renders it competent not only to recruit RXR into a heterodimer but also to conformationally silence the ability of its RXR partner to bind 9-cis RA and dissociate the heterodimer. Additional probing of protein-protein interactions has revealed that VDR also binds to basal transcription factor IIB (TFIIB) and, in the presence of 1,25(OH)2D3, an RXR-VDR-TFIIB ternary complex can be created in solution. Moreover, for transcriptional activation by 1,25(OH)2D3, both VDR and RXR require an intact short amphipathic alpha-helix, known as AF-2, positioned at their extreme C-termini. Because the AF-2 domains participate neither in VDR-RXR heterodimerization nor in TFIIB association, it is hypothesized that they contact, in a ligand-dependent fashion, transcriptional coactivators such as those of the steroid receptor coactivator family, constituting yet a third protein-protein interaction for VDR. Therefore, in VDR-mediated transcriptional activation, 1,25(OH)2D3 binding to VDR alters the conformation of the ligand binding domain such that it: (i) engages in strong heterodimerization with RXR to facilitate VDRE binding, (ii) influences the RXR ligand binding domain such that it is resistant to the binding of 9-cis RA but active in recruiting coactivator to its AF-2 and (iii) presents the AF-2 region in VDR for coactivator association. The above events, including bridging by coactivators to the TATA binding protein and associated factors, may position VDR such that it is able to attract TFIIB and the balance of the RNA polymerase II transcription machinery, culminating in repeated transcriptional initiation of VDRE-containing, vitamin D target genes. Such a model would explain the action of 1,25(OH)2D3 to elicit bone remodeling by stimulating osteoblast and osteoclast precursor gene expression, while concomitantly triggering the termination of its hormonal signal by inducing the 24-OHase catabolizing enzyme.

Combination of metformin and 9-cis retinoic acid increases apoptosis in C6 glioma stem-like cells

Glioblastoma (GBM) is the most commonly diagnosed type of brain cancer and the leading cause of brain cancer-related death. GBM contains a subpopulation of tumor-propagating glioblastoma stem-like cells that are thought to drive cancer progression and recurrence. Although several clinical trials are ongoing to explore new chemotherapeutic agents to treat GBM, the use of metformin (Met), a first-line drug for type 2 diabetes mellitus, in cancer remains controversial. Here, we show that combining Met with 9-cis retinoic acid (9-cis RA) reduced the proliferation rate of C6-GSCs (glioblastoma stem-like cells) in vitro. The results of flow cytometric analysis showed that treatment with 9-cis RA for 24 h induced 4.5% early and 38.0% late apoptosis in C6-GSCs. Twenty-four hours of Met treatment induced 23.6% early and 33.5% late apoptosis in C6-GSCs. Combination of Met and 9-cis RA treatment significantly increased both early and late apoptosis to 30.4% and 55.4%, respectively. The present findings suggest that not only 9-cis RA but also Met has the potential to induce early and late apoptotic GSCs death by affecting the functional cytoplasmic and nuclear organelles. At the protein level, there was increased cleaved caspase-3 but decreased procaspase-3 expression in Met-, 9-cis RA- and Met+9-cis RA-treated C6 GSCs, as detected by western blotting. The ratio of cleaved caspase-3/procaspase-3 was 1.6 times higher in Met+9-cis RA-treated groups compared to control. Ultimately, a combination of Met and 9-cis RA might be a possible therapeutic target for the treatment of GBM.

Role of Chicoric Acid and 13-Cis Retinoic Acid in Mycobacterium tuberculosis Infection Control by Human U937 Macrophage.

Mycobacterium tuberculosis (Mtb) survives and proliferates within the main cells of the innate immune system, macrophages. The goal of our study was to investigate the immunostimulatory effects of 13-cis retinoic acid (RA) and chicoric acid (CA) in human U937 macrophages against H37Ra Mtb infection by evaluating its potential role in the cell surface expression of HLA-DR, CD14 molecules as well as nitric oxide (NO) production and prevention of the Mtb growth within macrophages. In this study, we investigated the effects of 13-cis RA and CA on Mtb-infected macrophages using flowcytometry and Griess methods, respectively. Moreover, inhibitory effect of 13-cis RA and CA on Mtb growth within macrophages were assessed using colony-forming unit. 13-Cis RA and CA enhanced the cell surface expression of HLA-DR and CD14 molecules on U937 macrophages and prevented the growth of Mtb within macrophages. In addition, 13-cis RA and CA, have increased NO generation compared to untreated control macrophages, significantly (p < 0.001). Both drugs have a significant inhibitory effect on Mtb growth but CA at the highest concentration was more potent than 13-cis RA (p < 0.05). The results of our study showed that infected U937 macrophages treated with 13-cis RA and CA represented significant increases in NO production, CD14 and HLA-DR expression and also prevents intracellular survival of Mtb. Therefore, 13-cis RA and CA may have a significant therapeutic approach in the control of Mtb infection.

Evidence for retinoic acid involvement in the regulation of vitellogenesis in the fresh water edible crab, Oziotelphusa senex senex

The possible involvement of 13-cis retinoic acid (CRA) in the regulation of ovarian development in Oziotelphusa senex senex was investigated. Injection of CRA, into avitellogenic crabs significantly increased ovarian index, oocyte diameter and ovarian vitellogenin levels. Injection of CRA also resulted in a significant increase in the secretory rates of mandibular organs and Y-organs and circulatory levels of the methyl farnesoate and ecdysteroids. Further, administration of CRA into avitellogenic crabs produced higher amounts of Retinoid X Receptor, Ecdysteroid Receptor, E75 and vitellogenin mRNAs in the hepatopancreas. Mandibular organ and Y-organ explants isolated from avitellogenic crabs secreted more of methyl farnesoate and ecdysteroids respectively when incubated with CRA. Taken together, these observations led us to hypothesize that CRA stimulates ecdysteroidogenesis and methyl farnesoate synthesis, up-regulates EcR, RXR and E75 expression in hepatopancreas, which then induces vitellogenin gene expression. Vitellogenin is subsequently taken up from hemolymph by ovaries ensuing in ovarian maturation.

Characterization and comparison of transcriptional activities of the retinoid X receptors by various organotin compounds in three prosobranch gastropods; Thais clavigera, Nucella lapillus and Babylonia japonica

Two cDNAs of RXR were isolated, for the first time, from the ivory shell, Babylonia japonica, and the transcriptional activities were tested in vitro to compare with other gastropod (Thais clavigera and Nucella lapillus) RXR isoforms. The transcriptional activities of all of these RXR isoforms were significantly induced by mammalian RXR agonist, 9-cis retinoic acid (9cRA). The transcriptional activity of T. clavigera RXR-1 was also examined by using 9cRA and 16 organotin compounds, and significant ligand-dependent transactivations were observed by 9cRA and 5 organotins (tributyltin (TBT), tetrabutyltin (TeBT), tripropyltin (TPrT), tricyclohexyltin (TcHT) and triphenyltin (TPhT)). These 5 organotins also induced significant transcriptional activities in N. lapillus and B. japonica RXR isoforms. These 4 organotins, except for TeBT, have been reported to promote the development of imposex after a month of a single injection each, using female T. clavigera. To investigate the function of gastropod RXR isoforms, the effects of mammalian specific pan-agonist, PA024, and pan-antagonist, HX531, were examined, and significant induction of transcriptional activity by PA024 was demonstrated in these gastropod RXR isoforms. The additions of HX531 significantly suppressed the transcriptional activities of these gastropod RXR isoforms by 9cRA and 5 organotins. Using the mammalian two retinoic acid response elements, the transcriptional activities by 2 agonists, 9cRA and PA024, were different among the RXR isoforms of each gastropod species. With retinoid X response element (RXRE), transcriptional activities of TcRXR-1, BjRXR-1, and NlRXRa were significantly higher than those of TcRXR-2, BjRXR-2, and NlRXRb. Transcriptional activities of TcRXR-2, BjRXR-2, and NlRXRb, however, were significantly higher than those of TcRXR-1, BjRXR-1, and NlRXRa with thyroid hormone response element, TREpal. Thus, induction of imposex in prosobranch gastropods is strongly suggested to be triggered by 9cRA and certain organotins, such as TBT and TPhT through the activation of RXRs. These gastropod RXRs might control the different gene transcription by forming homo- or heterodimer complex with their own isoforms. These findings will contribute to our understanding of the fundamentals of the endocrine system in molluscs, particularly on RXR signaling pathway.

Long-term remission of recurren pityriasis versicolor with short-term systemic isotretinoin therapy

Although Pityriasis versicolor PV well responds to medical therapy recurrence is a common problem and management of recurrent and chronic PV is a challange sotretinoin cis retinoic acid is a vitamin A derivative decreases sebaceous gland size and sebum production up to Although the efficiency of isotretinoin is well known in acne and acne related disorders literature regarding its use in PV is scarce We present here a year old man succesfully treated and achieved long term remission with oral isotretinoin therapy who was suffering from diffuse recurrent PV for nearly years We believe that low dose and short term isotretinoin may be a good therapeutic option for recurrent and chronic PV

ICAM-1 upregulation is not required for retinoic acid-induced human eosinophil survival

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.