Detection of retinoic acid receptor antagonist contamination in the aquatic environment of the Kinki region of Japan

Retinoic acid receptor (RAR) antagonists are potential toxic compounds that can cause teratogenesis in vertebrates. This study was conducted to evaluate the occurrence of RAR antagonist contamination in aquatic environments and identify its potential sources in detail. To accomplish this, the RAR antagonistic activities of surface waters of two rivers (the Yodo River and the Ina River) and influents and effluents of municipal wastewater treatment plants (WWTPs) in the Kinki region of Japan were investigated using a yeast two-hybrid assay. In the investigated rivers, remarkable RAR antagonistic activities were detected relatively consistently in specific regions, although the levels varied with time, and tended to increase downstream of municipal WWTPs. Investigations of WWTPs also revealed that RAR antagonists were present at remarkably high levels in municipal wastewater, and that RAR antagonist contamination remained in effluent after activated sludge treatments. Comparison of the concentration factors that reduced 50% of the RAR agonistic activity of 10(-7) M all-trans retinoic acid (IC50) for selected river water and WWTP effluent samples revealed that the contamination levels were greater in effluent (IC50: concentration factors of 92-313) than river water (IC50: concentration factors of 10.2-68.9). These results indicate that municipal WWTPs could be an important source of RAR antagonist contamination in the receiving rivers. Fractionations with high-performance liquid chromatography directed by the bioassay indicated that there were multiple RAR antagonists in municipal wastewater. Although a trial to identify the causative compounds in municipal wastewater was not completed, multiple bioactive peaks that should be studied further were isolated. This study clarified the occurrence of novel endocrine disrupting chemicals (i.e., RAR antagonists) in the aquatic environment at the watershed level and identified their possible source for the first time, which suggests the need of further studies to identify the causative compounds and to assess possible ecological risks associated with the contamination.

Rexinoids isolated from Sophora tonkinensis with a gene expression profile distinct from the synthetic rexinoid bexarotene

The retinoid X receptor (RXR) plays a critical role in transcriptional regulation via formation of an RXR homodimer or heterodimers with partner nuclear receptors. Despite the numerous beneficial effects, only a limited number of naturally occurring RXR agonists are known. In this report, two prenylated flavanones (1 and 2) isolated from Sophora tonkinensis were identified as new rexinoids that preferentially activated RXRs, relative to the retinoic acid receptor. The activities of 1 and 2 were the most potent among naturally occurring rexinoids, yet 2 orders of magnitude lower than the synthetic rexinoid bexarotene. Compounds 1 and 2 activated particular RXR heterodimers in a manner similar to bexarotene. A microarray assay followed by quantitative real-time polymerase chain reaction analyses on RNAs isolated from C2C12 myotubes treated with 1 or 2 demonstrated that they significantly increased mRNA levels of lipoprotein lipase, angiopoietin-like protein 4, and heme oxygenase-1. In contrast, bexarotene preferentially potentiated transcription of genes involved in lipogenesis and lipid metabolism such as sterol regulatory element-binding protein-1, fatty acid synthase, and apolipoprotein D by a liver X receptor agonist. In this study, we have demonstrated that two newly identified naturally occurring rexinoids, 1 and 2, possess properties different from bexarotene.

Hepatitis C virus pathogen associated molecular pattern (PAMP) triggers production of lambda-interferons by human plasmacytoid dendritic cells

Plasmacytoid Dendritic Cells (pDCs) represent a key immune cell in the defense against viruses. Through pattern recognition receptors (PRRs), these cells detect viral pathogen associated molecular patterns (PAMPs) and initiate an Interferon (IFN) response. pDCs produce the antiviral IFNs including the well-studied Type I and the more recently described Type III. Recent genome wide association studies (GWAS) have implicated Type III IFNs in HCV clearance. We examined the IFN response induced in a pDC cell line and ex vivo human pDCs by a region of the HCV genome referred to as the HCV PAMP. This RNA has been shown previously to be immunogenic in hepatocytes, whereas the conserved X-region RNA is not. We show that in response to the HCV PAMP, pDC-GEN2.2 cells upregulate and secrete Type III (in addition to Type I) IFNs and upregulate PRR genes and proteins. We also demonstrate that the recognition of this RNA is dependent on RIG-I-like Receptors (RLRs) and Toll-like Receptors (TLRs), challenging the dogma that RLRs are dispensable in pDCs. The IFNs produced by these cells in response to the HCV PAMP also control HCV replication in vitro. These data are recapitulated in ex vivo pDCs isolated from healthy donors. Together, our data shows that pDCs respond robustly to HCV RNA to make Type III Interferons that control viral replication. This may represent a novel therapeutic strategy for the treatment of HCV.

[Successful treatment of acute promyelocytic leukemia complicated with autoimmune hepatitis-induced portal hypertension with all-trans retinoic acid]

A 35-year-old man admitted to the hospital for oral hemorrhage was diagnosed with acute promyelocytic leukemia (APL). Remission from APL was achieved by induction therapy with all-trans retinoic acid (ATRA); the PML/RARA fusion gene was not detected on PCR analysis. Despite complete molecular remission, severe persistent pancytopenia, massive ascites, and renal failure were observed. The liver surface appeared rough and irregular on computed tomographic images. On the basis of the liver biopsy results, we diagnosed his condition as portal hypertension due to autoimmune hepatitis. Indocyanine green test showed good residual function of the liver, and therefore, 2 courses of consolidation therapy were administered; chemotherapy was stopped because of severe pancytopenia due to portal hypertension. Instead of continuing the consolidation therapy, maintenance therapy involving 8 rounds of ATRA monotherapy (45 mg/m(2), days1∼14) was initiated. Portal hypertension did not progress further with this maintenance therapy and therefore it was continued. The patient has been in remission from APL ever since, and no relapses have occurred since the past 5 years. These results suggest that ATRA can be used for long-term therapy in such cases.

Identification of a naturally occurring rexinoid, honokiol, that activates the retinoid X receptor

Screening of a total of 86 crude drugs for retinoid X receptor (RXR) ligands demonstrated that the methanol extract of the bark of Magnolia obovata markedly activated the transcriptional activity of RXRalpha in luciferase reporter assays. Thereafter, honokiol (1) was isolated as a constituent able to activate RXR selectively as a natural rexinoid, but not RARalpha. The activity of 1 was more potent than those of phytanic acid and docosahexaenoic acid, both of which are known to be natural RXR agonists. Honokiol (1) is capable of activating a RXR/LXR heterodimer, resulting in the induction of ATP-binding cassette transporter A1 mRNA and protein expression in RAW264.7 cells, as well as an increase in [(3)H]cholesterol efflux from peritoneal macrophages. These effects of 1 were enhanced synergistically in the presence of an LXR agonist, 22(R)-hydroxycholesterol. The results obtained demonstrate that 1, a newly identified natural rexinoid, regulates the functions of RXR/LXR heterodimer and abrogates foam cell formation by the induction of ABCA1 via activation of the RXR/LXR heterodimer.

New complexities in helper T cell fate determination and the implications for autoimmune diseases

Recently, new complexities in cell fate decision for helper T cells have emerged. One new lineage, which has come to be called Th17 cells, selectively produces proinflammatory cytokines including interleukin-17 (IL-17, A and F), IL-21, and IL-22. In conjunction with transforming growth factor beta-1 (TGFbeta-1), IL-6, IL-21, and IL-23, which activate the transcription factor, signal transducer, and activator of transcription 3 (Stat3), the expression of another transcription factor, retinoic acid-related orphan receptor-gammat (RORgammat) leads to the differentiation of Th17 cells in mice. Other cytokines including IL-2, IL-4, interferon-gamma (IFN-gamma), and IL-27 inhibit Th17 differentiation. However, IL-2 acting with TGFbeta-1 induces differentiation of naïve CD4+ T cells to become regulatory T cells (Tregs). Th17 cells are now known to play an important role not only in the pathogenesis of inflammation and autoimmune diseases, but also host defense against extracellular bacteria. Conversely, extensive data substantiate the role of Tregs as essential in maintenance of peripheral tolerance. Selectively targeting Tregs and Th17 cells are likely to be important strategies in the treatment of inflammatory and autoimmune diseases in humans.

Role of retinoids in differentiation and growth of embryonal carcinoma cells

To study how retinoids promote differentiation and inhibit proliferation of embryonal carcinoma (EC) cells, we have followed their intracellular fate. Retinoic acid (RA) is effectively metabolized to more polar compounds by many EC lines. Unlike RA, retinol is slowly metabolized. Our inability to detect conversion of retinol to RA might indicate that the two retinoids elicit their effects on EC cells in different ways. Retinol added to cultures quickly appears in the nuclear fraction; the proportion associated with nuclei after detergent extraction is initially very low but increases with time. Retinol and RA might be translocated to nuclei by their respective binding proteins [cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP)]: isolated EC nuclei have specific, independent binding sites for both holoproteins but not their ligands. CRABP cannot be detected in the nucleoplasm of untreated EC cells, but activity is measurable after cells are exposed to RA. Interestingly, incubation with retinol promotes movement of both CRBP and CRABP into the nucleoplasmic fraction. Finally, we have demonstrated that brief exposure to RA dramatically reduces the cloning efficiency of EC cells. Since some cells are unaffected even by lengthy exposures to RA whereas the growth of their progeny is inhibited, we suggest that EC cells can become epigenetically refractory to RA.

[Effect on induction of differentiation of Tca8113 cells affected by abscisic acid in vitro]

OBJECTIVE

To approach the effects on induction of differentiation of Tca8113 cells affected by abscisic acid.

METHODS

The changes of surface differentiation markers, cell configuration, restrain of cell growth and the expression of Caspase-3 mRNA were examined by using inverted-phase contrast microscope, immunohistochemistry (IHC) and in situ hybridization in vitro. The dependablity between the surface differentiation markers and Caspase-3 mRNA was analysed.

RESULTS

The restraint of cell growth in ABA groups was higher than that of the control group (P<0.05). There was a trend that the tumor cell had transformed the normal cell. Furthermore, the time-dosage dependent relationship existed in the inhibition rate of tumor cells. The results showed that the expressions of Involucrin protein, retinoic acid receptor beta (RARbeta) and Caspase-3 mRNA in experimental group had been higher than that of control group. There was a significance between the different concentration experimental groups at 24 h (P<0.05). Moreover, the positive correlation existed among the Involucrin, RARbeta and Caspase-3 mRNA at the time of 12 hour and 24 hour (P<0.05).

CONCLUSION

The possible mechanism is that abscisic acid acted on the tumor cell and raised the level of RARbeta gene through combining the correlative receptors so that increased the expression of Involucrin protein and promoted the activity of Caspase-3 and resulted in apoptosis of tumor cell.

Acyclic Retinoid Inhibits Neointima Formation Through Retinoic Acid Receptor Beta-Induced Apoptosis

Objectives— Acyclic retinoid (ACR) is a synthetic retinoid with a high safety profile that has been pursued with high expectations for therapeutic use in prevention (recurrence) and treatment of malignancies. With the objective of addressing the therapeutic potential in the cardiovasculature, namely neointima formation, effects of ACR on neointima formation and the involved mechanisms were investigated.

Methods and Results— ACR was administered to cuff-injured mice which showed inhibition of neointima formation. Investigation of involved mechanisms at the cellular and molecular levels showed that ACR induces apoptosis of neointimal cells and this to be mediated by selective induction of retinoic-acid receptor β (RARβ) which shows growth inhibitory and proapoptotic effects on smooth muscle cells.

Conclusion— We show that ACR inhibits neointima formation by inducing RARβ which in turn inhibits cell growth and induces apoptosis. The retinoid, ACR, may be potentially exploitable for treatment and prevention of neointima formation.

Regulation of Leydig cell steroidogenesis by extracellular signal-regulated kinase 1/2: role of protein kinase A and protein kinase C signaling

The steroidogenic acute regulatory (StAR) protein plays a central role in the regulation of steroid biosynthesis. While steroidogenesis is influenced by many processes, their modes of actions, in a few cases, remain obscure. In this study, we explored the mechanism of action of one such signaling pathway, the extracellular signal-regulated kinase 1/2 (ERK1/2), in regulating StAR expression and steroidogenesis in conjunction with the protein kinase A (PKA) and protein kinase C (PKC) pathways. Using MA-10 mouse Leydig tumor cells, we demonstrate that the activation of PKC and PKA signaling, by phorbol-12-myristate-13-acetate (PMA) and dibutyryl cAMP (dbcAMP)/human chorionic gonadotropin (hCG) respectively, was able to phosphorylate ERK1/2, an event markedly decreased by an upstream kinase inhibitor, U0126. Treatment with PMA enhanced StAR protein expression (associated with a slight increase in progesterone synthesis) but not its phosphorylation (P-StAR), which, in contrast, coordinately increased in response to dbcAMP/hCG. Inhibition of ERK1/2 activity by U0126 decreased PMA-treated StAR expression but increased dbcAMP/hCG-mediated StAR and P-StAR; however, progesterone levels were attenuated. U0126 was found to affect StAR expression and steroidogenesis both at the transcriptional and translational levels. Further studies demonstrated that the effect of U0126 on PMA- and dbcAMP/hCG-mediated StAR expression and steroid synthesis was tightly correlated with the expression of dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene 1 (DAX-1) and scavenger receptor class B type 1 (SR-B1). In fact, both DAX-1 and SR-B1 appear to play important roles in hormone-regulated steroidogenesis. These findings clearly demonstrate that the ERK1/2 signaling cascade involved in regulating StAR expression and steroid synthesis is mediated by multiple factors and pathways and is stimulus specific in mouse Leydig cells.

Cytodifferentiation by retinoids, a novel therapeutic option in oncology: rational combinations with other therapeutic agents

Retinoic acid (RA) and derivatives are promising antineoplastic agents endowed with both therapeutic and chemopreventive potential. Although the treatment of acute promyelocytic leukemia with all-trans retinoic acid is an outstanding example, the full potential of retinoids in oncology has not yet been explored and a more generalized use of these compounds is not yet a reality. One way to enhance the therapeutic and chemopreventive activity of RA and derivatives is to identify rational combinations between these compounds and other pharmacological agents. This is now possible given the information available on the biochemical and molecular mechanisms underlying the biological activity of retinoids. At the cellular level, the antileukemia and anticancer activity of retinoids is the result of three main actions, cytodifferentiation, growth inhibition, and apoptosis. Cytodifferentiation is a particularly attractive modality of treatment and differentiating agents promise to be less toxic and more specific than conventional chemotherapy. This is the result of the fact that cytotoxicity is not the primary aim of differentiation therapy. At the molecular level, retinoids act through the activation of nuclear retinoic acid receptor-dependent and -independent pathways. The cellular pathways and molecular networks relevant for retinoid activity are modulated by a panoply of other intracellular and extracellular pathways that may be targeted by known drugs and other experimental therapeutics. This chapter aims to summarize and critically discuss the available knowledge in the field.

[Therapeutic results with apl 93 protocol in acute promyelocytic leukemia (34 cases)]

BACKGROUND

Acute promyelocytic leukaemia (APL) account for approximately 10% to 15% of all AML in most reports. Clinical features includes the presence in 80% to 90% of patients of a severe hemorrhagic syndrome, a specific balanced translocation between chromosomes 15 and 17 with a fusion of a large pert of the retinoic acid receptor a gene (RARa) on chromosome 17 to a part of the promyelocytic leukaemia (PML) gene on chromosome 15. More than 75% of patients (under 65 years of age) can be cured, with the application of a combination of anthracyclines and all-trans retinoic acid (ATRA), followed by maintenance therapy.

AIM

of the study was to assess of the therapeutic management of APL 93 protocol in acute promyelocytic leukemia.

METHODS

We present here the results of a retrospective study concerning 34 patients with APL included between 1998 and 2004 in the APL 93 protocol : 20 in group B and 14 in group C. CR was 82 %.

RESULTS

Failure is only due to toxic death (18%) Event free survival at 4 years is 63,47% with relapse rate at 14.25%. Overall survival at 4 years is 69,72%. Our results are acceptable and can be improved with reduction of failure due to toxic death, probably with omission of cytarabine from induction and consolidation adapted by the Spanish PETHEMA Group.

Bovine Early Embryonic Development and Vitamin A

Vitamin A and its derivatives, collectively termed as retinoids, have been paid attention in recent years because of their effects in bovine reproduction. However, the role of retinoids in the pre-implantation period continues to be largely unexplored, in contrast to later stages of development. Retinoids control cell growth, differentiation and death through binding to specific nuclear receptors by retinoic acid and other active metabolites. This paper reviews how retinoids can influence early embryonic development in cattle through their influence on the follicle, the extrafollicular oocyte and the pre-implantation embryo itself.

Stereospecificity and PAX6 function direct Hoxd4 neural enhancer activity along the antero-posterior axis

The antero-posterior (AP) and dorso-ventral (DV) patterning of the neural tube is controlled in part by HOX and PAX transcription factors, respectively. We have reported on a neural enhancer of Hoxd4 that directs expression in the CNS with the correct anterior border in the hindbrain. Comparison to the orthologous enhancer of zebrafish revealed seven conserved footprints including an obligatory retinoic acid response element (RARE), and adjacent sites D, E and F. Whereas enhancer function in the embryonic CNS is destroyed by separation of the RARE from sites D-E-F by a half turn of DNA, it is rescued by one full turn, suggesting stereospecific constraints between DNA-bound retinoid receptors and the factor(s) recognizing sites D-E-F. Alterations in the DV trajectory of the Hoxd4 anterior expression border following mutation of site D or E implicated transcriptional regulators active across the DV axis. We show that PAX6 specifically binds sites D and E in vitro, and use chromatin immunoprecipitation to demonstrate recruitment of PAX6 to the Hoxd4 neural enhancer in mouse embryos. Hoxd4 expression throughout the CNS is reduced in Pax6 mutant Sey(Neu) animals on embryonic day 8. Additionally, stage-matched zebrafish embryos having decreased pax6a and/or pax6b activity display malformed rhombomere boundaries and an anteriorized hoxd4a expression border. These results reveal an evolutionarily conserved role for Pax6 in AP-restricted expression of vertebrate Hoxd4 orthologs.

Comparison of selective retinoic acid receptor– and retinoic X receptor–mediated efficacy, tolerance, and survival in cutaneous t-cell lymphoma

Primary cutaneous T-cell lymphomas are non-Hodgkin's lymphomas with varied clinical presentation and prognosis. The most common subtypes of cutaneous T-cell lymphomas are the epidermotropic variants mycosis fungoides and Sézary syndrome. Treatment of mycosis fungoides has encompassed a variety of modalities including the use of retinoids with several studies evaluating their efficacy. The reported benefits and duration of response have varied in published data. The biological effect of retinoids is mediated by specific receptor families, retinoic acid receptor (RAR) and retinoic X receptor (RXR), with subsequently altered gene expression. There are no data available on cutaneous T-cell lymphomas that compare RAR and RXR retinoids. The objective of our retrospective, nonrandomized, single-center study was to compare the response, survival outcomes, and toxic effects in our phase II trial of the RAR-specific retinoid, all-trans retinoic acid, with clinical use of the RXR-specific retinoid, bexarotene, in patients with mycosis fungoides/Sézary syndrome who have relapsed. There was no statistical difference in response rates (12% vs 21%), response duration (20.5 vs 7.3 months), event-free survival time (4 vs 5 months), or median survival when corrected for length of follow-up. Both have favorable toxicity profiles that can be managed with medications. The toxicity profile caused by bexarotene seems to be more limited to laboratory values and better tolerated, although generally associated with more severe grades of toxicity. In conclusion, both retinoids have modest objective response rates and, therefore, most likely will have limited impact as monotherapeutic agents. However, the immunomodulatory effects of RAR and RXR retinoids provide a rational basis for using retinoids in combination with other biologic immune response modifiers, phototherapy, or cytotoxic chemotherapy.

All-trans retinoic acid directly up-regulates thrombopoietin transcription in human bone marrow stromal cells

OBJECTIVE

All-trans retinoic acid (ATRA) has been used as the first-line therapy for patients with acute promyelocytic leukemia (APL). We previously reported that ATRA increased serum thrombopoietin (TPO) levels accompanied by thrombocytosis during ATRA therapy for APL. In this study, we investigated the mechanism of transcriptional regulation of TPO gene by ATRA using human bone marrow stromal cells.

PATIENTS AND METHODS

Real time reverse transcriptase polymerase chain reaction and Western blotting were performed to quantify TPO mRNA and protein levels in cells from the human bone marrow stromal cell line KM101. Luciferase-based reporter assay, electrophoretic mobility shift assay (EMSA), and chromatin immunoprecipitation (ChIP) assay were performed to identify a retinoic acid responsive element in the promoter region of TPO gene (TPO-RARE).

RESULTS

TPO mRNA expression was up-regulated by approximately 2.9 times 8 hours after stimulation with 10(-6) M ATRA in KM101 cells. In contrast, ATRA did not alter TPO mRNA expression in cells from the human hepatoma cell line HepG2. Protein level of KM101 cells also was increased with 10(-6) M ATRA for 48 hours in KM101 cells. We found the synthesized RARalpha protein bound to [gamma-32P]-labeled TPO-RARE probe and its binding was competed by adding 200x amount of cold TPO-RARE probe by EMSA. In addition, [gamma-32P]-labeled TPO-RARE probe bound to KM101 nuclear protein extract was supershifted by anti-RARalpha antibody and modified by treatment with ATRA. The relative luciferase activity of TPO gene was increased by 2.2x and the histone H4 was acetylated through TPO-RARE after ATRA stimulation in KM101 cells by ChIP assay.

CONCLUSION

These data support the direct up-regulation of TPO transcription by ATRA stimulation in human bone marrow stromal cells and propose one of the mechanisms of thrombocytosis during ATRA therapy for APL.

The role of the orphan nuclear receptor, liver receptor homologue-1, in the regulation of human corpus luteum 3beta-hydroxysteroid dehydrogenase type II

After ovulation, ovarian 3beta-hydroxysteroid dehydrogenase type II (HSD3B2) expression increases to enhance the shift of steroidogenesis toward progesterone biosynthesis. Steroidogenic factor-1 (SF-1) is a transcription factor for several genes encoding steroidogenic enzymes. However, the level of SF-1 expression decreases in the human corpus luteum (CL) after ovulation. Liver receptor homolog-1 (LRH-1) is another member of the orphan nuclear receptor family. We hypothesize that LRH-1, rather than SF-1, plays an essential role in the regulation of corpus luteum steroidogenesis. Semiquantitative RT-PCR and real-time PCR were performed to quantify the level of LRH-1 expression and correlate with HSD3B2 level. Cell transfection, mutation analysis, and EMSA were performed to examine the role of LRH-1 in the regulation of HSD3B2. LRH-1 expression was higher in CL, compared with mature ovarian follicles. Cotransfection of granulosa cells with HSD3B2 and LRH-1 resulted in a 10-fold increase of transcription. DAX-1 inhibited LRH-1-stimulated HSD3B2, which was maintained in the presence of dibutyryl cAMP. Mutation of the either of the two putative LRH-1 binding sites, which were confirmed by EMSA, in the HSD3B2 promoter decreased LRH-1 stimulation. Our findings suggest that LRH-1 is highly expressed in CL, and it plays an essential role in the regulation of HSD3B2.

9cUAB30, an RXR specific retinoid, and/or tamoxifen in the prevention of methylnitrosourea-induced mammary cancers

Studies were performed in female Sprague-Dawley rats to determine the efficacy of a new RXR specific retinoid (9cUAB30) when combined with tamoxifen in the prevention of mammary cancers and to determine various pharmacokinetic parameters of the retinoid. When administered by gavage, 9cUAB30 was rapidly absorbed and had a serum t(1/2) of 13.5 h. Since the retinoid was administered in the diet for the chemoprevention study, a 28-day study in which 9cUAB30 was given at dose levels of 200, 400, and 600 mg/kg diet revealed fairly constant serum levels regardless of dose or length of treatment; possibly accounting for the observed low toxicity of this compound. When suboptimal doses of 9cUAB30 were given in the methylnitrosourea (MNU)-induced mammary cancer model, the following average number of mammary cancers were observed: 9cUAB30 (150 mg/kg diet), 4.3; tamoxifen (0.4 mg/kg diet), 4.6; 9cUAB30 (150 mg/kg diet)+tamoxifen (0.4 mg/kg diet), 2.6; and controls, 6.0. Thus, the combination of the agents resulted in an increased effect in preventing mammary cancers; suggesting that cancer cell proliferation was inhibited by the compounds blocking different pathways.