Regulation of hematopoiesis by retinoid signaling

The pathogenic role of retinoid nuclear receptor signaling in cancer and metabolic syndromes

The retinoid nuclear receptor pathway, activated by the vitamin A metabolite retinoic acid, has been extensively investigated for over a century. This study has resulted in conflicting hypotheses about how the pathway regulates health and how it should be pharmaceutically manipulated. These disagreements arise from a fundamental contradiction: retinoid agonists offer clear benefits to select patients with rare bone growth disorders, acute promyelocytic leukemia, and some dermatologic diseases, yet therapeutic retinoid pathway activation frequently causes more harm than good, both through acute metabolic dysregulation and a delayed cancer-promoting effect. In this review, we discuss controlled clinical, mechanistic, and genetic data to suggest several disease settings where inhibition of the retinoid pathway may be a compelling therapeutic strategy, such as solid cancers or metabolic syndromes, and also caution against continued testing of retinoid agonists in cancer patients. Considerable evidence suggests a central role for retinoid regulation of immunity and metabolism, with therapeutic opportunities to antagonize retinoid signaling proposed in cancer, diabetes, and obesity.

Discrete regulatory modules instruct hematopoietic lineage commitment and differentiation

Lineage commitment and differentiation is driven by the concerted action of master transcriptional regulators at their target chromatin sites. Multiple efforts have characterized the key transcription factors (TFs) that determine the various hematopoietic lineages. However, the temporal interactions between individual TFs and their chromatin targets during differentiation and how these interactions dictate lineage commitment remains poorly understood. Here we perform dense, daily, temporal profiling of chromatin accessibility (DNase I-seq) and gene expression changes (total RNA-seq) along ex vivo human erythropoiesis to comprehensively define developmentally regulated DNase I hypersensitive sites (DHSs) and transcripts. We link both distal DHSs to their target gene promoters and individual TFs to their target DHSs, revealing that the regulatory landscape is organized in distinct sequential regulatory modules that regulate lineage restriction and maturation. Finally, direct comparison of transcriptional dynamics (bulk and single-cell) and lineage potential between erythropoiesis and megakaryopoiesis uncovers differential fate commitment dynamics between the two lineages as they exit the stem and progenitor stage. Collectively, these data provide insights into the temporally regulated synergy of the cis- and the trans-regulatory components underlying hematopoietic lineage commitment and differentiation.

RXRA DT448/9PP generates a dominant active variant capable of inducing maturation in acute myeloid leukemia cells

RARA and RXRA contribute to myeloid maturation in both mice and humans, and deletion of Rxra and Rxrb augments leukemic growth in mice. While defining the domains of RXRA that are required for anti-leukemic effects in murine KMT2A-MLLT3 leukemia cells, we unexpectedly identified RXRA DT448/9PP as a constitutively active variant capable of inducing maturation and loss of their proliferative phenotype. RXRA DT448/9PP was associated with ligand-independent activity in reporter assays, with enhanced co-activator interactions, reduced engraftment in vivo, and activation of myeloid maturation transcriptional signatures that overlapped with those of cells treated with the potent RXRA agonist bexarotene, suggestive of constitutive activity that leads to leukemic maturation. Phenotypes of RXRA DT448/9PP appear to differ from those of two other RXRA mutations with forms of constitutive activity (F318A and S427F), in that DT448/9PP activity was resistant to mutations at critical ligand-interacting amino acids (R316A/L326A) and was resistant to pharmacological antagonists, suggesting it may be ligand-independent. These data provide further evidence that activated retinoid X receptors can regulate myeloid maturation and provide a novel constitutively active variant that may be germane for broader studies of retinoid X receptors in other settings.

Targeting the Microenvironment in MDS: The Final Frontier

Myelodysplastic syndromes (MDS) are a heterogeneous group of malignant disorders of hematopoietic stem and progenitor cells (HSPC), mainly characterized by ineffective hematopoiesis leading to peripheral cytopenias and progressive bone marrow failure. While clonal dominance is nearly universal at diagnosis, most genetic mutations identified in patients with MDS do not provide a conspicuous advantage to the malignant cells. In this context, malignant cells alter their adjacent bone marrow microenvironment (BME) and rely on cell extrinsic factors to maintain clonal dominance. The profoundly disturbed BME favors the myelodysplastic cells and, most importantly is detrimental to normal hematopoietic cells. Thus, the MDS microenvironment not only contributes to the observed cytopenias seen in these patients but could also negatively impact the engraftment of normal, allogeneic HSPCs in patients with MDS undergoing bone marrow transplant. Therefore, successful therapies in MDS should not only target the malignant cells but also reprogram their bone marrow microenvironment. Here, we will provide a synopsis of how drugs currently used or on the verge of being approved for the treatment of MDS may achieve this goal.

Effect of High-dose Vitamin A Supplementation in Children With Sickle Cell Disease: A Randomized, Double-blind, Dose-finding Pilot Study

Suboptimal vitamin A status (serum retinol <30 µg/dL) is associated with poor clinical outcomes in children with the hemoglobin-SS disease (HbSS), and supplementation with the recommended daily allowance of retinol is ineffective in improving vitamin A status. In a single-center randomized blinded dose-finding pilot study, we compared vitamin A and nutritional status in children with HbSS to healthy children and explored the impact of high-dose supplementation on the primary outcome serum vitamin A status. Exploratory outcomes included hematologic, nutritional, immunologic, and muscle function status in children with HbSS. A mixed-effects linear regression model evaluated associations between vitamin A dose, serum retinol, and exploratory outcomes. Twenty healthy children participated, and 22 subjects with HbSS were randomized to oral 3000 or 6000 IU/d retinol for 8 weeks; 21 subjects completed all evaluations. Serum retinol, growth, and nutritional status were all suboptimal in HbSS subjects at baseline, and supplementation did not change vitamin A status. Fetal hemoglobin (Δ=2.5, 95% confidence interval [CI], 0.5-4.3), mean corpuscular volume (Δ=2.7, 95% CI, 0.7-4.7), mean corpuscular hemoglobin (Δ=1.4, 95% CI, 0.5-2.3), and mean corpuscular hemoglobin concentration (Δ=0.5, 95% CI, 0.1-0.9) all improved with supplementation. Mild improvements in erythrocyte indices, growth status, and muscle function occurred independent of hydroxyurea use.

Prevalence and Risk Factors for Iron Deficiency in Adults With Cystic Fibrosis

BACKGROUND

Iron deficiency is common in cystic fibrosis (CF), but previous prevalence studies often reported results confounded by acute exacerbations. This single-center retrospective study aimed to identify the prevalence of iron deficiency in a stable adult CF population, identify the risk factors associated with iron deficiency, and compare common laboratory indicators of iron status.

METHODS

Medical charts of 105 patients aged 18-67 were reviewed to determine the prevalence of anemia. Of these patients, a subgroup of 67 were included in analyses of iron deficiency, defined as serum ferritin < 12 ng/mL and/or percent transferrin saturation (TSAT) < 16%. Data on sex, age, body mass index, anemia status, vitamin deficiencies, presence of comorbidities, colonization with Pseudomonas aeruginosa, and use of acid blockers and CF transmembrane conductance regulator modulators were collected to evaluate relationship of iron deficiency with these clinical factors. κ agreements between serum iron, ferritin, transferrin, and TSAT were compared.

RESULTS

In this stable CF population, the prevalence of iron deficiency was 41.8% (n = 67), and the prevalence of anemia was 33.3% (n = 105). Iron deficiency was associated with presence of anemia (P < .001), vitamin A deficiency (P = .012), and moderate (P = .047) and severe lung disease (P = .045) compared with mild lung disease. Transferrin agreed poorly with other iron status indicators.

CONCLUSION

Iron deficiency is common in CF, although prevalence rates can vary widely depending on the laboratory parameters used. CF centers should consider routine screening for iron deficiency.

BMS 493 Modulates Retinoic Acid-Induced Differentiation During Expansion of Human Hematopoietic Progenitor Cells for Islet Regeneration

Cellular therapies are emerging as a novel treatment strategy for diabetes. Thus, the induction of endogenous islet regeneration in situ represents a feasible goal for diabetes therapy. Umbilical cord blood-derived hematopoietic progenitor cells (HPCs), isolated by high aldehyde dehydrogenase activity (ALDH^hi), have previously been shown to reduce hyperglycemia after intrapancreatic (iPan) transplantation into streptozotocin (STZ)-treated nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) mice. However, these cells are rare and require ex vivo expansion to reach clinically applicable numbers for human therapy. Therefore, we investigated whether BMS 493, an inverse retinoic acid receptor agonist, could prevent retinoic acid-induced differentiation and preserve islet regenerative functions during expansion. After 6-day expansion, BMS 493-treated cells showed a twofold increase in the number of ALDH^hi cells available for transplantation compared with untreated controls. Newly expanded ALDH^hi cells showed increased numbers of CD34 and CD133-positive cells, as well as a reduction in CD38 expression, a marker of hematopoietic cell differentiation. BMS 493-treated cells showed similar hematopoietic colony-forming capacity compared with untreated cells, with ALDH^hi subpopulations producing more colonies than low aldehyde dehydrogenase activity subpopulations for expanded cells. To determine if the secreted proteins of these cells could augment the survival and/or proliferation of β-cells in vitro, conditioned media (CM) from cells expanded with or without BMS 493 was added to human islet cultures. The total number of proliferating β-cells was increased after 3- or 7-day culture with CM generated from BMS 493-treated cells. In contrast to freshly isolated ALDH^hi cells, 6-day expansion with or without BMS 493 generated progeny that were unable to reduce hyperglycemia after iPan transplantation into STZ-treated NOD/SCID mice. Further strategies to reduce retinoic acid differentiation during HPC expansion is required to expand ALDH^hi cells without the loss of islet regenerative functions.

RARα2 and PML-RAR similarities in the control of basal and retinoic acid induced myeloid maturation of acute myeloid leukemia cells

Treatment of acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA) is the first example of targeted therapy. In fact, the oncogenic fusion-protein (PML-RAR) typical of this leukemia contains the retinoid-nuclear-receptor RARα. PML-RAR is responsible for the differentiation block of the leukemic blast. Besides PML-RAR, two endogenous RARα proteins are present in APL blasts, i.e. RARα1 and RARα2. We developed different cell populations characterized by PML-RAR, RARα2 and RARα1 knock-down in the APL-derived NB4 cell-line. Unexpectedly, silencing of PML-RAR and RARα2 results in similar increases in the constitutive expression of several granulocytic differentiation markers. This is accompanied by enhanced expression of the same granulocytic markers upon exposure of the NB4 blasts to ATRA. Silencing of PML-RAR and RARα2 causes also similar perturbations in the whole genome gene-expression profiles of vehicle and ATRA treated NB4 cells. Unlike PML-RAR and RARα2, RARα1 knock-down blocks ATRA-dependent induction of several granulocytic differentiation markers. Many of the effects on myeloid differentiation are confirmed by over-expression of RARα2 in NB4 cells. RARα2 action on myeloid differentiation does not require the presence of PML-RAR, as it is recapitulated also upon knock-down in PML-RAR-negative HL-60 cells. Thus, relative to RARα1, PML-RAR and RARα2 exert opposite effects on APL-cell differentiation. These contrasting actions may be related to the fact that both PML-RAR and RARα2 interact with and inhibit the transcriptional activity of RARα1. The interaction surface is located in the carboxy-terminal domain containing the D/E/F regions and it is influenced by phosphorylation of Ser-369 of RARα1.

Vitamin A, endocrine tissues and hormones: interplay and interactions

Vitamin A (retinol) is a micronutrient critical for cell proliferation and differentiation. In adults, vitamin A and metabolites such as retinoic acid (RA) play major roles in vision, immune and brain functions, and tissue remodelling and metabolism. This review presents the physiological interactions of retinoids and endocrine tissues and hormonal systems. Two endocrine systems have been particularly studied. In the pituitary, retinoids targets the corticotrophs with a possible therapeutic use in corticotropinomas. In the thyroid, retinoids interfere with iodine metabolism and vitamin A deficiency aggravates thyroid dysfunction caused by iodine-deficient diets. Retinoids use in thyroid cancer appears less promising than expected. Recent and still controversial studies investigated the relations between retinoids and metabolic syndrome. Indeed, retinoids contribute to pancreatic development and modify fat and glucose metabolism. However, more detailed studies are needed before planning any therapeutic use. Finally, retinoids probably play more minor roles in adrenal and gonads development and function apart from their major effects on spermatogenesis.

Low-dose decitabine plus all-trans retinoic acid in patients with myeloid neoplasms ineligible for intensive chemotherapy

In our previous in vitro trials, decitabine and all-trans retinoic acid (ATRA) demonstrated synergistic effects on growth inhibition, differentiation, and apoptosis in SHI-1 cells; in K562 cells, ATRA enhanced the effect of decitabine on p16 demethylation, and the combination of the two drugs was found to activate RAR-β expression (p16 and RAR-β are two tumor suppressor genes). On the rationale of our in vitro trials, we used low-dose decitabine and ATRA to treat 31 myeloid neoplasms deemed ineligible for intensive chemotherapy. The regimen consisted of decitabine at the dose of 15 mg/m(2) intravenously over 1 h daily for consecutive 5 days and ATRA at the dose of 20 mg/m(2) orally from day 1 to 28 except day 4 to 28 in the first cycle, and the regimen was repeated every 28 days. After 6 cycles, decitabine treatment was stopped, and ATRA treatment was continued for maintenance treatment. Treated with a median of 2 cycles (range 1-6), 7 patients (22.6 %) achieved complete remission (CR), 7 (22.6 %) marrow CR (mCR), and 4 (12.9 %) partial remission (PR). The overall remission (CR, mCR, and PR) rate was 58.1 %, and the best response (CR and mCR) rate was 45.2 %. The median overall survival (OS) was 11.0 months, the 1-year OS rate was 41.9 %, and the 2-year OS rate was 26.6 %. In univariate analyses, age, performance status, comorbidities, white blood cell counts and platelets at diagnosis, percentage of bone marrow blasts, karyotype, and treatment efficacy demonstrated no impacts on OS (P > 0.05, each). Main side effects were tolerable hematologic toxicities. In conclusion, low-dose decitabine plus ATRA is a promising treatment for patients with myeloid neoplasms judged ineligible for intensive chemotherapy.

Vitamin A deficiency modulates iron metabolism independent of hemojuvelin (Hfe2) and bone morphogenetic protein 6 (Bmp6) transcript levels

BACKGROUND

Considering that vitamin A deficiency modulates hepcidin expression and consequently affects iron metabolism, we evaluated the effect of vitamin A deficiency in the expression of genes involved in the hemojuvelin (HJV)-bone morphogenetic protein 6 (BMP6)-small mothers against decapentaplegic protein (SMAD) signaling pathway.

METHODS

Male Wistar rats were treated: control AIN-93G diet (CT), vitamin A-deficient diet (VAD), iron-deficient diet (FeD), vitamin A- and iron-deficient diet (VAFeD), or 12 mg all-trans retinoic acid (atRA)/kg diet.

RESULTS

Vitamin A deficiency (VAD) increased hepatic Bmp6 and Hfe2 mRNA levels and down-regulated hepatic Hamp, Smad7, Rarα, and intestinal Fpn1 mRNA levels compared with the control. The FeD rats showed lower hepatic Hamp, Bmp6, and Smad7 mRNA levels compared with those of the control, while in the VAFeD rats only Hamp and Smad7 mRNA levels were lower than those of the control. The VAFeD diet up-regulated intestinal Dmt1 mRNA levels in relation to those of the control. The replacement of retinyl ester by atRA did not restore hepatic Hamp mRNA levels; however, the hepatic Hfe2, Bmp6, and Smad7 mRNA levels were similar to the control. The atRA rats showed an increase of hepatic Rarα mRNA levels and a reduction of intestinal Dmt1 mRNA and Fpn1 levels compared with those of the control.

CONCLUSIONS

The HJV-BMP6-SMAD signaling pathway that normally activates the expression of hepcidin in iron deficiency is impaired by vitamin A deficiency despite increased expression of liver Bmp6 and Hfe2 mRNA levels and decreased expression of Smad7 mRNA. This response may be associated to the systemic iron deficiency and spleen iron retention promoted by vitamin A deficiency.

Pathways of retinoid synthesis in mouse macrophages and bone marrow cells

In vivo pathways of natural retinoid metabolism and elimination have not been well characterized in primary myeloid cells, even though retinoids and retinoid receptors have been strongly implicated in regulating myeloid maturation. With the use of a upstream activation sequence-GFP reporter transgene and retrovirally expressed Gal4-retinoic acid receptor α in primary mouse bone marrow cells, we identified 2 distinct enzymatic pathways used by mouse myeloid cells ex vivo to synthesize retinoic acid receptor α ligands from free vitamin A metabolites (retinyl acetate, retinol, and retinal). Bulk Kit(+) bone marrow progenitor cells use diethylaminobenzaldehyde-sensitive enzymes, whereas bone marrow-derived macrophages use diethylaminobenzaldehyde-insensitive enzymes to synthesize natural retinoic acid receptor α-activating retinoids (all-trans retinoic acid). Bone marrow-derived macrophages do not express the diethylaminobenzaldehyde-sensitive enzymes Aldh1a1, Aldh1a2, or Aldh1a3 but instead, express Aldh3b1, which we found is capable of diethylaminobenzaldehyde-insensitive synthesis of all trans-retinoic acid. However, under steady-state and stimulated conditions in vivo, diverse bone marrow cells and peritoneal macrophages showed no evidence of intracellular retinoic acid receptor α-activating retinoids, despite expression of these enzymes and a vitamin A-sufficient diet, suggesting that the enzymatic conversion of retinal is not the rate-limiting step in the synthesis of intracellular retinoic acid receptor α-activating retinoids in myeloid bone marrow cells and that retinoic acid receptor α remains in an unliganded configuration during adult hematopoiesis.

UFBP1, a Key Component of the Ufm1 Conjugation System, Is Essential for Ufmylation-Mediated Regulation of Erythroid Development

The Ufm1 conjugation system is an ubiquitin-like modification system that consists of Ufm1, Uba5 (E1), Ufc1 (E2), and less defined E3 ligase(s) and targets. The biological importance of this system is highlighted by its essential role in embryogenesis and erythroid development, but the underlying mechanism is poorly understood. UFBP1 (Ufm1 binding protein 1, also known as DDRGK1, Dashurin and C20orf116) is a putative Ufm1 target, yet its exact physiological function and impact of its ufmylation remain largely undefined. In this study, we report that UFBP1 is indispensable for embryonic development and hematopoiesis. While germ-line deletion of UFBP1 caused defective erythroid development and embryonic lethality, somatic ablation of UFBP1 impaired adult hematopoiesis, resulting in pancytopenia and animal death. At the cellular level, UFBP1 deficiency led to elevated ER (endoplasmic reticulum) stress and activation of unfolded protein response (UPR), and consequently cell death of hematopoietic stem/progenitor cells. In addition, loss of UFBP1 suppressed expression of erythroid transcription factors GATA-1 and KLF1 and blocked erythroid differentiation from CFU-Es (colony forming unit-erythroid) to proerythroblasts. Interestingly, depletion of Uba5, a Ufm1 E1 enzyme, also caused elevation of ER stress and under-expression of erythroid transcription factors in erythroleukemia K562 cells. By contrast, knockdown of ASC1, a newly identified Ufm1 target that functions as a transcriptional co-activator of hormone receptors, led to down-regulation of erythroid transcription factors, but did not elevate basal ER stress. Furthermore, we found that ASC1 was associated with the promoters of GATA-1 and Klf1 in a UFBP1-dependent manner. Taken together, our findings suggest that UFBP1, along with ASC1 and other ufmylation components, play pleiotropic roles in regulation of hematopoietic cell survival and differentiation via modulating ER homeostasis and erythroid lineage-specific gene expression. Modulating the activity of this novel ubiquitin-like system may represent a novel approach to treat blood-related diseases such as anemia.

Protein modification by Ubiquitin (Ub) and Ubiquitin-like proteins (Ubl) plays pivotal roles in a wide range of cellular functions and signaling pathways. The Ufm1 conjugation system is a novel ubiquitin-like system, yet its biological functions and working mechanism remains poorly understood. UFBP1 is a putative Ufm1 target that has been implicated in several signaling pathways but little is known regarding its in vivo function. In this report, by using multiple knockout mouse models, we demonstrate that UFBP1 is essential for murine development and blood cell development. While germ-line deletion of UFBP1 caused defective red blood cell development and embryonic lethality, somatic ablation of UFBP1 impaired production of mature red blood cells and other types of hematopoietic cells. We found that depletion of UFBP1 led to elevated stress in the endoplasmic reticulum that in turn caused cell death of hematopoietic stem cells. Furthermore, UFBP1 deficiency diminished expression of key transcription factors essential for red blood cell development. Taken together, our study provides strong genetic evidence for the essential role of UFBP1 as well as other components of the Ufm1 system in hematopoietic development. Therefore, the ufmylation pathway may represent a novel therapeutic target in treatment of blood diseases.

Maternal vitamin A supplementation increases natural antibody concentrations of preadolescent offspring in rural Nepal

OBJECTIVE

B1a lymphocytes-which constitutively produce most natural antibodies (NAb)-arise from an early wave of progenitors unique to fetal life. Vitamin A regulates early lymphopoiesis. In animals, deficiency during this critical period compromises B1 cell populations. The aim of this study was to investigate the effect of maternal supplementation with vitamin A or β-carotene from preconception through lactation on NAb concentrations of offspring.

METHODS

Participants (N = 290) were born to participants of a cluster-randomized, placebo-controlled trial of weekly maternal vitamin A or β-carotene supplementation (7000 μg retinol equivalents) conducted in Sarlahi, Nepal (1994-1997) and assessed at ages 9 to 13 y (2006-2008). Serum retinol was measured by reversed-phase high-performance liquid chromatography at mid-pregnancy and 3 mo of age. Enzyme-linked immunosorbent assay (ELISA) was used to measure children's plasma NAb concentrations at 9 to 13 y.

RESULTS

Unadjusted geometric mean concentrations were 20.08 U/mL (95% confidence interval [CI], 17.82-22.64) in the vitamin A group compared with 17.64 U/mL (95% CI, 15.70-19.81) and 15.96 U/mL (95% CI, 13.43-18.96) in the β-carotene and placebo groups (P = 0.07), respectively. After adjustment, maternal vitamin A supplementation was associated with a 0.39 SD increase in NAb concentrations (P = 0.02). The effect was mediated by infant serum retinol in our statistical models. Although girls had 1.4-fold higher NAb concentrations (P < 0.001), sex did not modify the vitamin A effect.

CONCLUSIONS

In an undernourished population, maternal vitamin A supplementation enhanced NAb concentrations of preadolescent children. We posit that this was due to a greater allotment of B1a precursors during fetal life and a sustained higher count of NAb-secreting B1a cells.

Retinoic Acid Improves a Hybridoma Culture in a Fructose-Based Medium by Up-Regulation of Fructose IncorporationviaRetinoid Nuclear Receptors

Fructose was focused on as an alternative sugar source to glucose in a hybridoma culture medium because it decreases lactate production during cultivation, leading to cell and product stability. But, not all human hybridoma cell lines grew well in a fructose-based serum-free medium. We found that the addition of all-trans-retinoic acid to the fructose-based medium improved the growth and monoclonal antibody production of hybridoma cell lines by up-regulation of fructose incorporation that represented increased expression of the fructose transporter, GLUT5. Selective activation of retinoid nuclear receptor by synthetic ligands showed that both retinoic acid receptors and retinoid X receptors might be related to the improvement of the fructose-based hybridoma culture. This study might be applicable to cell cultures susceptible to lactate and pH changes as well as hybridoma cultures.

Erythroid-extrinsic regulation of normal erythropoiesis by retinoic acid receptors

Vitamin A and its derivatives (retinoids) are important regulators of haematopoiesis, acting via retinoic acid receptors (RARs). Epidemiological studies indicated an association of vitamin A deficiency with anaemia in humans. To define the requirements of RARs in erythropoiesis, we evaluated erythroid parameters in RAR germ-line deficient and conditional knock out mice with erythroid specific deletion of RARs. Adult RARγ(-/-) mice were anaemic, however, Epor-Cre Rara(fl/fl) , Epor-Cre Rarg(fl/fl) and Epor-Cre Rara(fl/fl) g(fl/fl) mice were normal, indicating a lack of an erythroid intrinsic RAR function. Therefore, erythroid-specific RAR function is dispensable for erythropoiesis and RARγ plays an erythroid extrinsic role in erythropoiesis.

Tgif1 regulates quiescence and self-renewal of hematopoietic stem cells

TG-interacting factor 1 (TGIF1) is a transcriptional repressor that can modulate retinoic acid and transforming growth factor β signaling pathways. It is required for myeloid progenitor cell differentiation and survival, and mutations in the TGIF1 gene cause holoprosencephaly. Furthermore, we have previously observed that acute myelogenous leukemia (AML) patients with low TGIF1 levels had worse prognoses. Here, we explored the role of Tgif1 in murine hematopoietic stem cell (HSC) function. CFU assays showed that Tgif1(-/-) bone marrow cells produced more total colonies and had higher serial CFU potential. These effects were also observed in vivo, where Tgif1(-/-) bone marrow cells had higher repopulation potential in short- and long-term competitive repopulation assays than wild-type cells. Serial transplantation and replating studies showed that Tgif1(-/-) HSCs exhibited greater self-renewal and were less proliferative and more quiescent than wild-type cells, suggesting that Tgif1 is required for stem cells to enter the cell cycle. Furthermore, HSCs from Tgif1(+/-) mice had a phenotype similar to that of HSCs from Tgif1(-/-) mice, while bone marrow cells with overexpressing Tgif1 showed increased proliferation and lower survival in long-term transplant studies. Taken together, our data suggest that Tgif1 suppresses stem cell self-renewal and provide clues as to how reduced expression of TGIF1 may contribute to poor long-term survival in patients with AML.

Impact of micronutrient fortification of yoghurt on micronutrient status markers and growth - a randomized double blind controlled trial among school children in Bangladesh

Background

Interventions providing foods fortified with multiple micronutrients can be a cost-effective and sustainable strategy to improve micronutrient status and physical growth of school children. We evaluated the effect of micronutrient-fortified yoghurt on the biochemical status of important micronutrients (iron, zinc, iodine, vitamin A) as well as growth indicators among school children in Bogra district of Bangladesh.

Methods

In a double-masked randomized controlled trial (RCT) conducted in 4 primary schools, 1010 children from classes 1–4 (age 6–9 years) were randomly allocated to receive either micronutrient fortified yoghurt (FY, n = 501) or non-fortified yoghurt (NFY, n = 509). For one year, children were fed with 60 g yoghurt everyday providing 30% RDA for iron, zinc, iodine and vitamin A. Anthropometric measurements and blood/urine samples were collected at base-, mid- and end-line. All children (FY, n = 278, NFY, n = 293) consenting for the end-line blood sample were included in the present analyses.

Results

Both groups were comparable at baseline for socio-economic status variables, micronutrient status markers and anthropometry measures. Compliance was similar in both the groups. At baseline 53.4% of the population was anemic; 2.1% was iron deficient (ferritin <15.0 μg/L and TfR > 8.3 mg/L). Children in the FY group showed improvement in Hb (mean difference: 1.5; 95% CI: 0.4-2.5; p = 0.006) as compared to NFY group. Retinol binding protein (mean diff: 0.05; 95% CI: 0.002-0.09; p = 0.04) and iodine levels (mean difference: 39.87; 95% CI: 20.39-59.35; p < 0.001) decreased between base and end-line but the decrease was significantly less in the FY group. Compared to NFY, the FY group had better height gain velocity (mean diff: 0.32; 95% CI: 0.05-0.60; p = 0.02) and height-for-age z-scores (mean diff: 0.18; 95% CI: 0.02-0.33; p = 0.03). There was no difference in weight gain velocity, weight-for-age z-scores or Body Mass Index z-scores.

Conclusion

In the absence of iron deficiency at baseline the impact on iron status would not be expected to be observed and hence cannot be evaluated. Improved Hb concentrations in the absence of a change in iron status suggest improved utilization of iron possibly due to vitamin A and zinc availability. Fortification improved height gain without affecting weight gain.

Trial registration

ClinicalTrial.gov: NCT00980733

Relationship between hemoglobin, serum retinol and habitual meat consumption in the elderly: a population-based study

Considering the scarcity of data on the relationship between hemoglobin, serum retinol and habitual meat consumption in the elderly, a cross-sectional population-based study was performed, which was representative of the population of a state capital in Northeastern Brazil, including 176 elderly aged between 60 and 90 years, who responded to questionnaires about habitual food consumption and socioeconomic aspects. Blood counts and serum retinol analyses were carried out. The prevalence of anemia was 9.58%, and 96% of elderly showing adequate serum retinol levels. The consumption of vitamin A and iron was adequate in 93.75% and 85%, respectively. There was no correlation between serum retinol and hemoglobin values (p=0.56), and as expected, there was a positive association between meat consumption and hemoglobin (p=0.02). Based on results obtained in this study, it was concluded that the maintenance of adequate vitamin A and meat intake in this population should be encouraged, which appears to be an effective intervention strategy to achieve appropriate serum retinol and hemoglobin values, and hence lower iron deficiency anemia rates.

Tail regression induced by elevated retinoic acid signaling in amphioxus larvae occurs by tissue remodeling, not cell death

The vitamin A derived morphogen retinoic acid (RA) is known to function in the regulation of tissue proliferation and differentiation. Here, we show that exogenous RA applied to late larvae of the invertebrate chordate amphioxus can reverse some differentiated states. Although treatment with the RA antagonist BMS009 has no obvious effect on late larvae of amphioxus, administration of excess RA alters the morphology of the posterior end of the body. The anus closes over, and gut contents accumulate in the hindgut. In addition, the larval tail fin regresses, although little apoptosis takes place. This fin normally consists of columnar epidermal cells, each characterized by a ciliary rootlet running all the way from an apical centriole to the base of the cell and likely contributing substantial cytoskeletal support. After a few days of RA treatment, the rootlet becomes disrupted, and the cell shape changes from columnar to cuboidal. Transmission electron microscopy (TEM) shows fragments of the rootlet in the basal cytoplasm of the cuboidal cell. A major component of the ciliary rootlet in amphioxus is the protein Rootletin, which is encoded by a single AmphiRootletin gene. This gene is highly expressed in the tail epithelial cells of control larvae, but becomes downregulated after about a day of RA treatment, and the breakup of the ciliary rootlet soon follows. The effect of excess RA on these epidermal cells of the larval tail in amphioxus is unlike posterior regression in developing zebrafish, where elevated RA signaling alters connective tissues of mesodermal origin. In contrast, however, the RA-induced closure of the amphioxus anus has parallels in the RA-induced caudal regression syndrome of mammals.

Retinoids: novel immunomodulators and tumour-suppressive agents?

Retinoids play important roles in the transcriptional activity of normal, degenerative and tumour cells. Retinoid analogues may be promising therapeutic agents for the treatment of immune disorders as different as type I diabetes and systemic lupus erythematosus. In addition, the use of retinoids in cancer treatment has progressed significantly in the last two decades; thus, numerous retinoid compounds have been synthesized and tested. In this paper, the actual or potential use of retinoids as immunomodulators or tumour-suppressive agents is discussed.

Retinoid agonist Am80-enhanced neutrophil bactericidal activity arising from granulopoiesis in vitro and in a neutropenic mouse model

Despite advances in the therapeutic use of recombinant granulocyte colony-stimulating factor (G-CSF) to promote granulopoiesis of human hematopoietic stem cells (HSCs), neutropenia remains one of the most serious complications of cancer chemotherapy. We discovered that retinoid agonist Am80 (tamibarotene) is more potent than G-CSF in coordinating neutrophil differentiation and immunity development. Am80-induced neutrophils (AINs) either in vitro or in neutropenic mouse model displayed strong bactericidal activities, similar to those of human peripheral blood neutrophils (PBNs) or mouse peripheral blood neutrophils (MPBNs) but markedly greater than did G-CSF–induced neutrophils (GINs). In contrast to GINs but similar to PBNs, the enhanced bacterial killing by AINs accompanied both better granule maturation and greater coexpression of CD66 antigen with the integrin β2 subunit CD18. Consistently, anti-CD18 antibody neutralized Am80-induced bactericidal activities of AINs. These studies demonstrate that Am80 is more effective than G-CSF in promoting neutrophil differentiation and bactericidal activities, probably through coordinating the functional interaction of CD66 with CD18 to enhance the development of neutrophil immunity during granulopoiesis. Our findings herein suggest a molecular rationale for developing new therapy against neutropenia using Am80 as a cost-effective treatment option.

Studies on HOXB4 expression during differentiation of human cytomegalovirus-infected hematopoietic stem cells into lymphocyte and erythrocyte progenitor cells

We investigated the role of homeobox B4 (HOXB4) mRNA/protein expression induced by human cytomegalovirus (HCMV) and/or all-trans retinoic acid (ATRA) in proliferation and committed differentiation of human cord blood hematopoietic stem cells (HSCs) into colony-forming-units of T-lymphocyte (CFU-TL) and erythroid (CFU-E) progenitors in vitro. Twelve cord blood samples were collected from the fetal placenta umbilical vein and cultured in vitro. The proliferation and differentiation of cord blood HSCs into CFU-TL and CFU-E were continuously disrupted with HCMV-AD169 and/or 6 × 10(-8) mol/l of ATRA. HOXB4 mRNA/protein expression in CFU-TL and CFU-E was detected in control, ATRA, HCMV and ATRA + HCMV groups on days 3, 7, and 12 of culture by fluorescent qRT-PCR/western blot. We found that HOXB4 mRNA/protein expression was detectable on day 3, increased on day 7 and was highest on day 12. HOXB4 mRNA/protein expression in HCMV group was downregulated compared with control group (P < 0.05). However, the levels were significantly upregulated in HCMV + ATRA group compared with HCMV group (P < 0.05). We concluded that the abnormal HOXB4 mRNA/protein expression induced by HCMV could play a role in hematopoietic damage. ATRA, at the concentration used, significantly up-regulated HOXB4 mRNA/protein expression in normal lymphocyte and erythrocyte progenitor cells as well as in HCMV-infected cells.

Aldehyde dehydrogenases are regulators of hematopoietic stem cell numbers and B-cell development

High levels of the aldehyde dehydrogenase isoform ALDH1A1 are expressed in hematopoietic stem cells (HSCs); however, its importance in these cells remains unclear. Consistent with an earlier report, we find that loss of ALDH1A1 does not affect HSCs. Intriguingly, however, we find that ALDH1A1 deficiency is associated with increased expression of the ALDH3A1 isoform, suggesting its potential to compensate for ALDH1A1. Mice deficient in ALDH3A1 have a block in B-cell development as well as abnormalities in cell cycling, intracellular signaling, and gene expression. Early B cells from these mice exhibit excess reactive oxygen species and reduced metabolism of reactive aldehydes. Mice deficient in both ALDH3A1 and ALDH1A1 have reduced numbers of HSCs as well as aberrant cell cycle distribution, increased reactive oxygen species levels, p38 mitogen-activated protein kinase activity and sensitivity to DNA damage. These findings demonstrate that ALDH3A1 can compensate for ALDH1A1 in bone marrow and is important in B-cell development, both ALDH1A1 and 3A1 are important in HSC biology; and these effects may be due, in part, to changes in metabolism of reactive oxygen species and reactive aldehydes.

Retinoid-regulated FGF8f secretion by osteoblasts bypasses retinoid stimuli to mediate granulocytic differentiation of myeloid leukemia cells

Signaling from the human hematopoietic stem cell (HSC) niche formed by osteoblastic cells regulates hematopoiesis. We previously found that retinoic acid receptor alpha (RARα), a transcription factor activated by retinoic acid (RA), mediates both granulocytic and osteoblastic differentiation. This effect depends on decreased phosphorylation of serine 77 of RARα (RARαS77) by the cyclin-dependent kinase-activating kinase (CAK) complex, a key cell-cycle regulator. In this article, we report that, by suppressing CAK phosphorylation of RARα, RA induces FGF8f to mediate osteosarcoma U2OS cell differentiation in an autocrine manner. By contrast, paracrine FGF8f secreted into osteoblast-conditioned medium by U2OS cells transduced with FGF8f or a phosphorylation-defective RARαS77 mutant, RARαS77A, bypasses RA stimuli to cross-mediate granulocytic differentiation of different types of human leukemic myeloblasts and normal primitive hematopoietic CD34(+) cells, possibly through modulating mitogen-activated protein kinase (MAPK) pathways. Further experiments using recombinant human FGF8f (rFGF8f) stimuli, antibody neutralization, and peptide blocking showed that paracrine FGF8f is required for mediating terminal leukemic myeloblast differentiation. These studies indicate a novel regulatory mechanism of granulocytic differentiation instigated by RA from the HSC niche, which links loss of CAK phosphorylation of RARα with paracrine FGF8f-mediated MAPK signaling to mediate leukemic myeloblast differentiation in the absence of RA. Therefore, these findings provide a compelling molecular rationale for further investigation of paracrine FGF8f regulation, with the intent of devising HSC niche-based FGF8f therapeutics for myeloid leukemia, with or without RA-resistance.

Nutritionally mediated programming of the developing immune system

A growing body of evidence highlights the importance of a mother's nutrition from preconception through lactation in programming the emerging organ systems and homeostatic pathways of her offspring. The developing immune system may be particularly vulnerable. Indeed, examples of nutrition-mediated immune programming can be found in the literature on intra-uterine growth retardation, maternal micronutrient deficiencies, and infant feeding. Current models of immune ontogeny depict a "layered" expansion of increasingly complex defenses, which may be permanently altered by maternal malnutrition. One programming mechanism involves activation of the maternal hypothalamic-pituitary-adrenal axis in response to nutritional stress. Fetal or neonatal exposure to elevated stress hormones is linked in animal studies to permanent changes in neuroendocrine-immune interactions, with diverse manifestations such as an attenuated inflammatory response or reduced resistance to tumor colonization. Maternal malnutrition may also have a direct influence, as evidenced by nutrient-driven epigenetic changes to developing T regulatory cells and subsequent risk of allergy or asthma. A 3rd programming pathway involves placental or breast milk transfer of maternal immune factors with immunomodulatory functions (e.g. cytokines). Maternal malnutrition can directly affect transfer mechanisms or influence the quality or quantity of transferred factors. The public health implications of nutrition-mediated immune programming are of particular importance in the developing world, where prevalent maternal undernutrition is coupled with persistent infectious challenges. However, early alterations to the immune system, resulting from either nutritional deficiencies or excesses, have broad relevance for immune-mediated diseases, such as asthma, and chronic inflammatory conditions like cardiovascular disease.

Increased blood oxidative stress in experimental menopause rat model: the effects of vitamin A low-dose supplementation upon antioxidant status in bilateral ovariectomized rats

Menopause has been reported to be associated with increased oxidative stress and metabolic disorders among women worldwide. Disarrangements in the redox state similar to those observed in women during the decline of ovarian hormonal activity can be obtained experimentally through rat bilateral ovariectomy. The search for alternative treatments to improve life quality in postmenopausal woman is really important. The aim of this study was to evaluate biochemical and oxidative stress parameters that distinguish sham-operated female rats from Wistar rats bilaterally ovariectomized (OVX). Additionally, we have also investigated the effects of retinol palmitate (a vitamin A supplement) low-dose supplementation (500 or 1500 IU/kg/day, during 30 days) upon blood and plasma antioxidant status in OVX rats. Ovariectomy caused an increase in body weight gain, pronounced uterine atrophy, decreased plasma triglycerides and increased total cholesterol levels, and reduced acid uric content. Moreover, we found increased blood peroxidase activities (catalase and glutathione peroxidase), decreased plasma non-enzymatic antioxidant defenses total reactive antioxidant potential and total antioxidant reactivity, decreased protein and non-protein SH levels, accompanied by increased protein oxidative damage (carbonyl). In addition, vitamin A low-dose supplementation was capable to ameliorate antioxidant status in OVX rats, restoring both enzymatic and non-enzymatic defenses, promoting reduction in plasma SH content, and decreasing protein oxidative damage levels. This is the first work in the literature showing that vitamin A at low dose may be beneficial in the treatment of menopause symptoms. Further studies will be made to better understand the effects of vitamin A supplementation in menopause rat model.

Rara haploinsufficiency modestly influences the phenotype of acute promyelocytic leukemia in mice

RARA (retinoic acid receptor alpha) haploinsufficiency is an invariable consequence of t(15;17)(q22;q21) translocations in acute promyelocytic leukemia (APL). Retinoids and RARA activity have been implicated in hematopoietic self-renewal and neutrophil maturation. We and others therefore predicted that RARA haploinsufficiency would contribute to APL pathogenesis. To test this hypothesis, we crossed Rara(+/-) mice with mice expressing PML (promyelocytic leukemia)-RARA from the cathepsin G locus (mCG-PR). We found that Rara haploinsufficiency cooperated with PML-RARA, but only modestly influenced the preleukemic and leukemic phenotype. Bone marrow from mCG-PR(+/-) × Rara(+/-) mice had decreased numbers of mature myeloid cells, increased ex vivo myeloid cell proliferation, and increased competitive advantage after transplantation. Rara haploinsufficiency did not alter mCG-PR-dependent leukemic latency or penetrance, but did influence the distribution of leukemic cells; leukemia in mCG-PR(+/-) × Rara(+/-) mice presented more commonly with low to normal white blood cell counts and with myeloid infiltration of lymph nodes. APL cells from these mice were responsive to all-trans retinoic acid and had virtually no differences in expression profiling compared with tumors arising in mCG-PR(+/-) × Rara(+/+) mice. These data show that Rara haploinsufficiency (like Pml haploinsufficiency and RARA-PML) can cooperate with PML-RARA to influence the pathogenesis of APL in mice, but that PML-RARA is the t(15;17) disease-initiating mutation.

Transforming growth factor beta2 is negatively regulated by endogenous retinoic acid during early heart morphogenesis

Vitamin A-deficient (VAD) quail embryos lack the vitamin A-active form, retinoic acid (RA) and are characterized by a phenotype that includes a grossly abnormal cardiovascular system that can be rescued by RA. Here we report that the transforming growth factor, TGFbeta2 is involved in RA-regulated cardiovascular development. In VAD embryos TGFbeta2 mRNA and protein expression are greatly elevated. The expression of TGFbeta receptor II is also elevated in VAD embryos but is normalized by treatment with TGFbeta2-specific antisense oligonucleotides (AS). Administration of this AS or an antibody specific for TGFbeta2 to VAD embryos normalizes posterior heart development and vascularization, while the administration of exogenous active TGFbeta2 protein to normal quail embryos mimics the excessive TGFbeta2 status of VAD embryos and induces VAD cardiovascular phenotype. In VAD embryos pSmad2/3 and pErk1 are not activated, while pErk2 and pcRaf are elevated and pSmad1/5/8 is diminished. We conclude that in the early avian embryo TGFbeta2 has a major role in the retinoic acid-regulated posterior heart morphogenesis for which it does not use Smad2/3 pathways, but may use other signaling pathways. Importantly, we conclude that retinoic acid is a critical negative physiological regulator of the magnitude of TGFbeta2 signals during vertebrate heart formation.

Retinoic acid enhances the generation of hematopoietic progenitors from human embryonic stem cell–derived hemato-vascular precursors

Current induction schemes directing hematopoietic differentiation of human embryonic stem cells (hESCs) are not well defined to mimic the sequential stages of hematopoietic development in vivo. Here, we report a 3-stage method to direct differentiation of hESCs toward hematopoietic progenitors in chemically defined mediums. In the first 2 stages, we efficiently generated T-positive primitive streak/mesendoderm cells and kinase domain receptor–positive (KDR+) platelet-derived growth factor receptor α–negative (PDGFRα−) hemato-vascular precursors sequentially. In the third stage, we found that cells in a spontaneous differentiation condition mainly formed erythroid colonies. Addition of all-trans retinoic acid (RA) greatly enhanced generation of hematopoietic progenitors in this stage while suppressing erythroid development. The RA-treated cells highly expressed definitive hematopoietic genes, formed large numbers of multilineage and myeloid colonies, and gave rise to greater than 45% CD45+ hematopoietic cells. When hematopoietic progenitors were selected with CD34 and C-Kit, greater than 95% CD45+ hematopoietic cells could be generated. In addition, we found that endogenous RA signaling at the second stage was required for vascular endothelial growth factor/basic fibroblast growth factor–induced hemato-vascular specification, whereas exogenously applied RA efficiently induced KDR−PDGFRα+ paraxial mesoderm cells. Our study suggests that RA signaling plays diverse roles in human mesoderm and hematopoietic development.

The retinoid signaling pathway inhibits hematopoiesis and uncouples from the Hox genes during hematopoietic development

Retinoic acid (RA) is a well-established inducer of Hox genes during development of neurectoderm, however effects of RA on Hox expression are poorly defined in mesoderm and not defined in the hematopoietic compartment. Both Hox genes and retinoid signaling have been suggested to modulate hematopoietic stem cell (HSC) self-renewal, supporting the notion that RA signaling might drive HSC self-renewal through Hox gene induction. Here, we investigate this possibility by comprehensively evaluating Hox gene expression using mouse embryonic stem cells differentiated in vitro. In unspecified mesoderm, we find that RA coordinately upregulates anterior 3' Hox genes from clusters A, B, and C, and downregulates posterior 5' Hox genes from clusters A-D. However, hematopoietic development of mesoderm was inhibited by RA, and we find further that retinoids are entirely dispensable for hematopoiesis in vitro. More surprisingly, in fully specified hematopoietic progenitors, Hox genes are refractory to regulation by RA, although other RA targets are normally regulated. Pulses of RA exposure demonstrate that the Hox complexes are decoupled from RA regulation progressively in lateral plate mesoderm as it undergoes hematopoietic specification. Thus, Hox genes are targets of the RA pathway only in selected cell types, and are clearly not regulated by RA in the earliest hematopoietic progenitors. We propose that the developmental uncoupling of the Hox complexes protects the Hox code from potential RA signaling centers as HSCs migrate or circulate during development.

Transforming growth-interacting factor (TGIF) regulates proliferation and differentiation of human myeloid leukemia cells

Transforming growth-interacting factor (TGIF) is a homeobox transcriptional repressor that has been implicated in holoprosencephaly and various types of cancer. TGIF is expressed in hematopoietic stem cells and modulates TGF-beta and retinoic acid (RA) signaling, both of which play an important role in hematopoiesis. We recently reported that TGIF's levels correlate inversely with survival in patients with acute myelogenous leukemia. Here we present the first direct evidence of a role for TGIF in myelopoiesis. We used short hairpin RNA interference to define the effects of TGIF knockdown on proliferation and differentiation of myeloid leukemia-derived cell lines. Decreased TGIF expression resulted in reduced proliferation and differentiation and lower expression of CEBPbeta, CEBPepsilon, PU.1 and RUNX1, key myeloid transcription factors. Furthermore, TGF-beta signaling was increased and RA signaling was decreased. Further insights into the molecular basis of TGIF's effects were provided by a genome-wide chromatin immunoprecipitation-based elucidation of TGIF target genes. Together, these data suggest that TGIF has an important role myelopoiesis and may regulate the balance between proliferation and differentiation. Reduced TGIF expression could tip the balance toward quiescence thus providing progenitor as well as hematopoietic stem cells protection from anti-cycle agents.

Function of retinoid acid receptor alpha and p21 in all-trans-retinoic acid-induced acute T-lymphoblastic leukemia apoptosis

All-trans-retinoic acid (ATRA) is a morphogenetic signalling molecule derived from vitamin A and is used clinically to target acute promyelocytic leukemia by inducing differentiation of immature blood cells. Retinoid signals are mediated by retinoic acid (RA) receptors (RARs) and retinoid X receptors (RXRs). Retinoic acid receptors consist of RARalpha, RARbeta and RARgamma isotypes. Among these components, RARalpha is preferentially bound to ATRA, which is used to treat acute T-lymphoblastic leukemia, yet the conditions and mechanisms remain unknown. In this study, we have demonstrated that, in human acute T-lymphoblastic leukemia Molt3 cells, inhibition of RA-induced proliferation results from massive cell death characterised by apoptosis. The effect of ATRA:RARalpha binding on apoptosis in Molt3 cells has been investigated. Consequently, it has been shown that, in RA-treated Molt3 cells, upregulation of p21 due to RA accompanies caspase 3/PARP activation which precedes the occurrence of apoptosis.

The preferentially expressed antigen in melanoma (PRAME) inhibits myeloid differentiation in normal hematopoietic and leukemic progenitor cells

The preferentially expressed antigen in melanoma (PRAME) is expressed in several hematologic malignancies, but either is not expressed or is expressed at only low levels in normal hematopoietic cells, making it a target for cancer therapy. PRAME is a tumor-associated antigen and has been described as a corepressor of retinoic acid signaling in solid tumor cells, but its function in hematopoietic cells is unknown. PRAME mRNA expression increased with chronic myeloid leukemia (CML) disease progression and its detection in late chronic-phase CML patients before tyrosine kinase inhibitor therapy was associated with poorer therapeutic responses and ABL tyrosine kinase domain point mutations. In leukemia cell lines, PRAME protein expression inhibited granulocytic differentiation only in cell lines that differentiate along this lineage after all-trans retinoic acid (ATRA) exposure. Forced PRAME expression in normal hematopoietic progenitors, however, inhibited myeloid differentiation both in the presence and absence of ATRA, and this phenotype was reversed when PRAME was silenced in primary CML progenitors. These observations suggest that PRAME inhibits myeloid differentiation in certain myeloid leukemias, and that its function in these cells is lineage and phenotype dependent. Lastly, these observations suggest that PRAME is a target for both prognostic and therapeutic applications.

Anemia after bariatric surgery: more than just iron deficiency

Bariatric surgery for morbid obesity is rapidly gaining popularity. Restrictive and/or malabsorptive surgical interventions result in dramatic weight loss with significantly decreased obesity-related morbidity and mortality. Anemia, which may affect as many as two-thirds of these patients, is of concern and generally thought to be caused by iron deficiency. Although iron deficiency in this population may be frequent given pouch hypoacidity, defunctionalized small bowel, and red meat intolerance, it may not account for all anemias seen. First, there is increasing evidence that obesity creates a state of chronic inflammation. Both iron deficiency anemia and anemia of chronic inflammation present with low serum iron levels. Most studies reporting anemia after bariatric surgery lack serum ferritin determinations so that the relative contribution of inflammation to anemia cannot be assessed. Second, a significant number of anemias after bariatric surgery remain unexplained and may be attributable to less frequently seen micronutrient deficiencies such as copper, fatsoluble vitamins A and E, or an imbalance in zinc intake. Third, although deficiencies of folate and vitamin B(12) are infrequent, study observation periods may be too short to detect anemia attributable to vitamin B(12) deficiency because vitamin B(12) storage depletion takes many years. This review is intended to increase awareness of the mechanisms of anemia above and beyond iron deficiency in the bariatric patient and provide healthcare providers with tools for a more thoughtful approach to anemia in this patient population.

Multi-micronutrient-fortified biscuits decreased prevalence of anemia and improved micronutrient status and effectiveness of deworming in rural Vietnamese school children

Concurrent micronutrient deficiencies are prevalent among Vietnamese school children. A school-based program providing food fortified with multiple micronutrients could be a cost-effective and sustainable strategy to improve health and cognitive function of school children. However, the efficacy of such an intervention may be compromised by the high prevalence of parasitic infestation. To evaluate the efficacy of school-based intervention using multi-micronutrient-fortified biscuits with or without deworming on anemia and micronutrient status in Vietnamese schoolchildren, a randomized, double-blind, placebo-controlled trial was conducted among 510 primary schoolchildren, aged 6-8 y, in rural Vietnam. Albendazole (Alb) (400 mg) or placebo was given at baseline. Nonfortified or multi-micronutrient-fortified biscuits including iron (6 mg), zinc (5.6 mg), iodine (35 microg), and vitamin A (300 microg retinol equivalents) were given 5 d/wk for 4 mo. Multi-micronutrient fortification significantly improved the concentrations of hemoglobin (+1.87 g/L; 95% CI: 0.78, 2.96), plasma ferritin (+7.5 microg/L; 95% CI: 2.8, 12.6), body iron (+0.56 mg/kg body weight; 95% CI: 0.29, 0.84), plasma zinc (+0.61 micromol/L; 95% CI: 0.26, 0.95), plasma retinol (+0.041 micromol/L; 95% CI: 0.001, 0.08), and urinary iodine (+22.49 micromol/L; 95% CI: 7.68, 37.31). Fortification reduced the risk of anemia and deficiencies of zinc and iodine by >40%. Parasitic infestation did not affect fortification efficacy, whereas fortification significantly enhanced deworming efficacy, with the lowest reinfection rates in children receiving both micronutrients and Alb. Multi-micronutrient fortification of biscuits is an effective strategy to improve the micronutrient status of Vietnamese schoolchildren and enhances effectiveness of deworming.

Drug resistance is dramatically restored by hedgehog inhibitors in CD34+ leukemic cells

Aberrant reactivation of hedgehog (Hh) signaling has been described in a wide variety of human cancers and in cancer stem cells. However, the contribution of Hh signaling to leukemic cell regulation has remained unclear. In this study, we assessed the possibility that Hh pathway activation contributes to the survival and drug resistance of cluster of differentiation (CD)34+ leukemia cells. Hh signaling in leukemic cell lines and primary leukemic cells was screened by reverse transcription - polymerase chain reaction (RT-PCR) and a Hh signaling reporter assay. We found that Hh signaling is active in several human acute myeloid leukemia (AML) cells, especially primary CD34+ leukemic cells and cytokine-responsive CD34+ cell lines such as Kasumi-1, Kasumi-3 and TF-1. These CD34+ cells express the downstream effectors glioma-associated oncogene homolog (GLI)1 or GLI2, indicative of active Hh signaling. Moreover, inhibition of Hh signaling with the naturally derived Smoothened antagonist cyclopamine, endogenous Hh inhibitor hedgehog-interacting protein or anti-hedgehog neutralizing antibody induced apoptosis after 48 h of exposure, although these CD34+ cell lines exhibited resistance to cytarabine (Ara-C). In contrast, cyclopamine failed to affect growth or survival in U937 and HL-60 cell lines that lack expression of Hh receptor components, confirming that the effect of Hh inhibition is specific. Furthermore, combination with 10 microM cyclopamine significantly reduced drug resistance of CD34+ cell lines and primary CD34+ leukemic cells to Ara-C. These results suggest that aberrant Hh pathway activation is a feature of some CD34+ myeloid leukemic cells and Hh inhibitors may have a therapeutic role in the treatment of AML.

A myelopoiesis-associated regulatory intergenic noncoding RNA transcript within the human HOXA cluster

We have identified an intergenic transcriptional activity that is located between the human HOXA1 and HOXA2 genes, shows myeloid-specific expression, and is up-regulated during granulocytic differentiation. The novel gene, termed HOTAIRM1 (HOX antisense intergenic RNA myeloid 1), is transcribed antisense to the HOXA genes and originates from the same CpG island that embeds the start site of HOXA1. The transcript appears to be a noncoding RNA containing no long open-reading frame; sucrose gradient analysis shows no association with polyribosomal fractions. HOTAIRM1 is the most prominent intergenic transcript expressed and up-regulated during induced granulocytic differentiation of NB4 promyelocytic leukemia and normal human hematopoietic cells; its expression is specific to the myeloid lineage. Its induction during retinoic acid (RA)-driven granulocytic differentiation is through RA receptor and may depend on the expression of myeloid cell development factors targeted by RA signaling. Knockdown of HOTAIRM1 quantitatively blunted RA-induced expression of HOXA1 and HOXA4 during the myeloid differentiation of NB4 cells, and selectively attenuated induction of transcripts for the myeloid differentiation genes CD11b and CD18, but did not noticeably impact the more distal HOXA genes. These findings suggest that HOTAIRM1 plays a role in the myelopoiesis through modulation of gene expression in the HOXA cluster.

Is there a role for all-trans retinoic acid in combination with recombinant erythropoetin in myelodysplastic syndromes? A report on 59 cases

Erythropoiesis-stimulating agents (ESAs) remain the first-line treatment of anemia in lower risk myelodysplastic syndromes (MDS) without 5q deletion. A preliminary report suggested that adding all-trans retinoic acid (ATRA) to ESAs may improve their erythroid response, particularly in patients with high endogenous erythropoietin (EPO) level, and may improve other cytopenias. We conducted a prospective multicenter study of EPO-beta and ATRA in anemic MDS patients with marrow blasts <10% and either previous ESA failure or relapse, endogenous EPO >500 U/l or other cytopenia(s) (absolute neutrophilic count <1.0 G/l or platelets <50 G/l). A total of 59 patients were evaluable after 12 weeks of treatment. The erythroid response rates according to IWG 2000 and 2006 criteria, respectively, were as follows: overall: 49 and 36%; patients with previous ESA failure (n=28): 43 and 32%; patients with endogenous EPO >500 U/l (n=18): 11 and 19%; patients transfused >2 red blood cells units/month (n=28) 43 and 39%. Only one neutrophil, but no platelet response, and no major side effect were observed. EPO-beta-ATRA combination appears a possible therapeutic option in anemia of MDS having failed an ESA alone, but not in patients with high endogenous EPO level, and does not improve neutropenia and thrombocytopenia.

Gene expression profiling of pulmonary mucosa-associated lymphoid tissue lymphoma identifies new biologic insights with potential diagnostic and therapeutic applications

We conducted comprehensive gene expression profiling (GEP) of primary pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma (n = 33) and compared the results to GEP of other B- and T-cell lymphomas and normal lymphocytes to identify novel markers and deregulated pathways. MALT has a prominent T-cell signature and a marginal zone/memory B-cell profile. Four novel transcripts were specifically overexpressed in MALT, and 2 of these, MMP7 and SIGLEC6, were validated at the protein level. GEP also revealed distinct molecular subsets in MALT. One subset, characterized by MALT1 translocations, showed overexpression of nuclear factor-kappaB (NF-KB) pathway genes but also was enriched for chemokine signaling pathways. Another subset showed increased plasma cells and a prominent plasma cell gene signature. By analyzing several genes with very high ("spiked") expression in individual cases, we identified clusters with different biologic characteristics, such as samples with MALT1 translocations having high expression of MALT1 and RARA, samples with plasmacytic differentiation having high FKBP11 expression, and samples with high RGS13 expression tending to have trisomy 3 and reactive follicles. In conclusion, MALT subgroups with distinct pathologic features defined by distinct groups of deregulated genes were identified. These genes could represent novel diagnostic and therapeutic targets.

Retinoic acid decreases adherence of murine myeloid dendritic cells and increases production of matrix metalloproteinase-9

Myeloid dendritic cells (DC) are professional antigen presenting cells (APC) that migrate to secondary lymphoid tissues upon antigen stimulation, where they activate naïve T cells. Vitamin A is essential for normal immune function. We investigated the ability of all-trans retinoic acid (atRA), a bioactive metabolite of vitamin A, to modulate DC adhesion in culture. Male BALB/cJ mouse bone marrow cells cultured with granulocyte-macrophage colony-stimulating factor in the presence of retinoic acid receptor (RAR) alpha-specific antagonist showed an increase in the percentage of developing DC that remained adherent compared with cells rescued with atRA treatment from d 8 to 10 of culture (P < 0.05). Replacement of the RARalpha antagonist with atRA on d 8 of the culture period decreased DC surface expression of the adhesion molecule CD11a (P < 0.0001) but not the gene expression. Rescue with atRA also dramatically increased gene and protein expression of pro-matrix metalloproteinase (MMP)-9 (P < 0.05). However, gene expression and protein production of tissue inhibitor of metalloproteinase (TIMP)-1 was unaffected by atRA rescue, altering the molar ratio of secreted pro-MMP-9:TIMP-1, resulting in a fold excess of pro-MMP-9 to its primary inhibitor (P < 0.05). These data suggest that atRA is essential to augment MMP-9 expression in myeloid DC and can alter their surface expression of adhesion molecules.

Retinoic acid receptor gamma activates receptor tyrosine kinase Tie1 gene transcription through transcription factor GATA4 in F9 stem cells

OBJECTIVE

The retinoic acid receptors (RARs) alpha, beta2, and gamma regulate specific subsets of target genes during all-trans retinoic acid (RA) induced differentiation of F9 teratocarcinoma stem cells. The Tie1 gene exhibited reduced expression in RA-treated F9 RARgamma-/- cells as compared to wild-type (WT) by microarray analysis. Our goal was to analyze the Tie1 gene, which encodes a surface receptor tyrosine kinase expressed in the hematovascular system.

MATERIALS AND METHODS

We assessed Tie1, Tie2, Flk1, Runx1, Peg/Mest2, and angiopoietin-1 and 2 mRNA levels and Tie1 promoter activity.

RESULTS

We showed that RARgamma, but not RARalpha or RARbeta2, is required for Tie1 promoter activation by RA. Treatment with a RARgamma selective agonist plus a retinoid X receptor agonist (LGD1069) increased Tie1 mRNA levels by 11- +/- 2.5-fold 48 hours after RA addition in F9 WT, but not in F9 RARgamma-/- cells, by quantitative reverse transcription polymerase chain reaction. Multiple putative GATA elements were identified in the Tie1 proximal promoter. RA increased GATA4 transcripts by 12- +/- 1-fold in F9 WT at 48 hours, but not in F9 RARgamma-/- cells. In addition, transfection of a GATA4 expression vector increased Tie1 promoter/luciferase activity in both RA-treated F9 WT and RARgamma-/- cells. Tie1 promoter deletion analyses indicated that a region of the promoter that possessed multiple GATA sites mediated the RA-associated Tie1 transcriptional increase.

CONCLUSIONS

Our results indicate that GATA4 plays a role in the RA/RARgamma-associated transcriptional activation of the Tie1 promoter. An understanding of RAR specificity in RA signaling should result in insights into hematopoietic stem cell signaling and potentially in improved therapies for several human diseases.

Localized rbp4 expression in the yolk syncytial layer plays a role in yolk cell extension and early liver development

BACKGROUND

The number of genes characterized in liver development is steadily increasing, but the origin of liver precursor cells and the molecular control of liver formation remain poorly understood. Existing theories about formation of zebrafish visceral organs emphasize either their budding from the endodermal rod or formation of independent anlage followed by their later fusion, but none of these is completely satisfactory in explaining liver organogenesis in zebrafish.

RESULTS

Expression of a gene encoding the retinol binding protein 4 (Rbp4) was analyzed in zebrafish. rbp4, which is expressed mainly in the liver in adults, was shown to be expressed in the yolk syncytial layer (YSL) during early embryogenesis. At 12-16 hpf rbp4 expression was restricted to the ventro-lateral YSL and later expanded to cover the posterior YSL. We demonstrated that rbp4 expression was negatively regulated by Nodal and Hedgehog (Hh) signalling and positively controlled by retinoic acid (RA). Knockdown of Rbp4 in the YSL resulted in shortened yolk extension as well as the formation of two liver buds, which could be due to impaired migration of liver progenitor cells. rbp4 appears also to regulate the extracellular matrix protein Fibronectin1 (Fn1) specifically in the ventro-lateral yolk, indicating a role of Fn1 in liver progenitor migration. Since exocrine pancreas, endocrine pancreas, intestine and heart developed normally in Rbp4 morphants, we suggest that rbp4 expression in the YSL is required only for liver development.

CONCLUSION

The characteristic expression pattern of rbp4 suggests that the YSL is patterned despite its syncytial nature. YSL-expressed Rbp4 plays a role in formation of both yolk extension and liver bud, the latter may also require migration of liver progenitor cells.

Intrinsic Retinoic Acid Receptor α-Cyclin-Dependent Kinase-Activating Kinase Signaling Involves Coordination of the Restricted Proliferation and Granulocytic Differentiation of Human Hematopoietic Stem Cells

Little is known about the mechanisms by which retinoic acid receptor alpha (RAR alpha) mediates the effects of retinoic acid (RA) to coordinate granulocytic proliferation/differentiation (P/D) transition. Cyclin-dependent kinase-activating kinase (CAK) complex, whose activity in phosphorylation of RAR alpha is determined by its targeting subunit ménage à trois 1 (MAT1), regulates G(1) exit, a cell cycle stage when cells commonly commit to proliferation or to differentiation. We previously found that in myeloid leukemia cells, the lack of RA-induced RAR alpha-CAK dissociation and MAT1 degradation suppresses cell differentiation by inhibiting CAK-dependent G(1) exit and sustaining CAK hyperphosphorylation of RAR alpha. This contrasts with our recent findings about the P/D transition in normal primitive hematopoietic cells, where MAT1 degradation proceeds intrinsically together with granulocytic development, in accord with dynamic expression of aldehyde dehydrogenases (ALDHs) 1A1 and 1B1, which catalyze RA synthesis. Blocking ALDH activity inhibits MAT1 degradation and granulocytic differentiation, whereas loss of RAR alpha phosphorylation by CAK induces RA-target gene expression and granulocytic differentiation. These studies suggest that the subversion of RAR alpha-CAK signaling during normal granulopoiesis is crucial to myeloid leukemogenesis and challenges the current paradigm that RA induces cell differentiation solely by transactivating target genes. Disclosure of potential conflicts of interest is found at the end of this article.

Retinoic acid enhances differentiation of v-myb-transformed monoblasts induced by okadaic acid

Differentiation of various leukemic cells can be induced by liganded retinoic acid receptors and protein phosphatase inhibitors. In this study, we explored the effects of okadaic acid (OA), the phosphatase inhibitor, and retinoic acid (RA) in v-myb-transformed monoblasts BM2. OA induced differentiation of BM2 monoblasts into macrophage-like cells, as documented by analyses of cell morphology, cell cycle, phagocytic activity, non-specific esterase activity, production of reactive oxygen species and expression of vimentin and Mo-1. In contrast to many other leukemic cell lines, BM2 cells do not respond to retinoic acid. However, once exposed to OA and RA simultaneously, BM2 cells differentiate along monocyte/macrophage pathway more efficiently. We conclude that RA enhances differentiation of v-myb-transformed monoblasts induced by protein phosphorylation.

Hydrophobic ligand binding properties of the human lipocalin apolipoprotein M

Apolipoprotein M (apoM) is a plasma protein associated mainly with HDL. ApoM is suggested to be important for the formation of prebeta-HDL, but its mechanism of action is unknown. Homology modeling has suggested apoM to be a lipocalin. Lipocalins share a structurally conserved beta-barrel, which in many lipocalins bind hydrophobic ligands. The aim of this study was to test the ability of apoM to bind different hydrophobic substances. ApoM was produced both in Escherichia coli and in HEK 293 cells. Characterization of both variants with electrophoretic and immunological methods suggested apoM from E. coli to be correctly folded. Intrinsic tryptophan fluorescence of both apoM variants revealed that retinol, all-trans-retinoic acid, and 9-cis-retinoic acid bound (dissociation constant = 2-3 microM), whereas other tested substances (e.g., cholesterol, vitamin K, and arachidonic acid) did not. The intrinsic fluorescence of two apoM mutants carrying single tryptophans was quenched by retinol and retinoic acid to the same extent as wild-type apoM, indicating that the environment of both tryptophans was affected by the binding. In conclusion, the binding of retinol and retinoic acid supports the hypothesis that apoM is a lipocalin. The physiological relevance of this binding has yet to be elucidated.