Minireview: Nuclear receptors, hematopoiesis, and stem cells

Associations among thyroid hormone levels and mean corpuscular volume in adults in the US: A cross-sectional examination of the NHANES 2007-2012 dataset

Mean corpuscular volume (MCV) is an important indicator used to determine the etiology of anemia and is associated with a variety of diseases. However, the link between thyroid function and MCV has yet to be clarified. This study was thus developed to assess relationships between thyroid function and MCV in a population of adults in the US. Results from the National Health and Nutrition Examination Survey study performed from 2007 to 2012 were used to conduct a cross-sectional analysis. Key thyroid-related variables included in this analysis were thyroid-stimulating hormone, total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), antithyroglobulin, thyroglobulin, and antithyroid peroxidase levels. Generalized linear regression models were employed when estimating associations between MCV quartiles and thyroid parameters in 8104 adults 18 + years of age. In these participants, the weighted mean (SD) MCV was 89.36 (0.16) fL, with thyroid-stimulating hormone levels of 1.86 (0.03) mIU/mL, FT3 levels of 3.20 (0.01) pg/mL, FT4 levels of 0.80 (0.01) ng/dL, TT3 levels of 115.09 (0.64) ng/dL, and TT4 levels of 7.81 (0.04) μg/dL. When analyses were not adjusted, higher MCV values were related to reduced serum levels of FT3, TT3, or TT4. Following adjustment for possible confounding variables, this significant negative correlation between MCV and levels of FT3, TT3, and TT4 remained, and subgroup analysis revealed that this negative correlation was present in the male group and in the age group >50 years, but not in the female group and in the age group less than or equal to 50 years. These results suggest a significant negative correlation between MCV and FT3, TT3, and TT4, and this negative correlation originated more from the male population and those older than 50 years of age. The underlying mechanisms warrant additional investigation.

Current investigations for liver fibrosis treatment: between repurposing the FDA-approved drugs and the other emerging approaches

Long-term liver injuries lead to hepatic fibrosis, often progressing into cirrhosis, liver failure, portal hypertension, and hepatocellular carcinoma. There is currently no effective therapy available for liver fibrosis. Thus, continuous investigations for anti-fibrotic therapy are ongoing. The main theme of anti-fibrotic investigation during recent years is the rationale-based selection of treatment molecules according to the current understanding of the pathology of the disease. The research efforts are mainly toward repurposing current FDA-approved drugs targeting etiological molecular factors involved in developing liver fibrosis. In parallel, investigations also focus on experimental small molecules with evidence to hinder or reverse the fibrosis. Natural compounds, immunological, and genetic approaches have shown significant encouraging effects. This review summarizes the efficacy and safety of current under-investigation antifibrosis medications targeting various molecular targets, as well as the properties of antifibrosis medications, mainly in phase II and III clinical trials.

Combined Naïve Bayesian, Chemical Fingerprints and Molecular Docking Classifiers to Model and Predict Androgen Receptor Binding Data for Environmentally- and Health-Sensitive Substances

Many chemicals that enter the environment, food chain, and the human body can disrupt androgen-dependent pathways and mimic hormones and therefore, may be responsible for multiple diseases from reproductive to tumor. Thus, modeling and predicting androgen receptor activity is an important area of research. The aim of the current study was to find a method or combination of methods to predict compounds that can bind to and/or disrupt the androgen receptor, and thereby guide decision making and further analysis. A stepwise procedure proceeded from analysis of protein structures from human, chimp, and rat, followed by docking and subsequent ligand, and statistics based techniques that improved classification gradually. The best methods used multivariate logistic regression of combinations of chimpanzee protein structural docking scores, extended connectivity fingerprints, and naïve Bayesians of known binders and non-binders. Combination or consensus methods included data from a variety of procedures to improve the final model accuracy.

Etiopathogenesis, Challenges and Remedies Associated With Female Genital Tuberculosis: Potential Role of Nuclear Receptors

Extra-pulmonary tuberculosis (EPTB) is recognized mainly as a secondary manifestation of a primary tuberculosis (TB) infection in the lungs contributing to a high incidence of morbidity and mortality. The TB bacilli upon reactivation maneuver from the primary site disseminating to other organs. Diagnosis and treatment of EPTB remains challenging due to the abstruse positioning of the infected organs and the associated invasiveness of sample acquisition as well as misdiagnosis, associated comorbidities, and the inadequacy of biomarkers. Female genital tuberculosis (FGTB) represents the most perilous form of EPTB leading to poor uterine receptivity (UR), recurrent implantation failure and infertility in females. Although the number of TB cases is reducing, FGTB cases are not getting enough attention because of a lack of clinical awareness, nonspecific symptoms, and inappropriate diagnostic measures. This review provides an overview for EPTB, particularly FGTB diagnostics and treatment challenges. We emphasize the need for new therapeutics and highlight the need for the exaction of biomarkers as a point of care diagnostic. Nuclear receptors have reported role in maintaining UR, immune modulation, and TB modulation; therefore, we postulate their role as a therapeutic drug target and biomarker that should be explored in FGTB.

History of Estrogen: Its Purification, Structure, Synthesis, Biologic Actions, and Clinical Implications

This mini-review summarizes key points from the Clark Sawin Memorial Lecture on the History of Estrogen delivered at Endo 2018 and focuses on the rationales and motivation leading to various discoveries and their clinical applications. During the classical period of antiquity, incisive clinical observations uncovered important findings; however, extensive anatomical dissections to solidify proof were generally lacking. Initiation of the experimental approach followed later, influenced by Claude Bernard's treatise "An Introduction to the Study of Experimental Medicine." With this approach, investigators began to explore the function of the ovaries and their "internal secretions" and, after intensive investigations for several years, purified various estrogens. Clinical therapies for hot flashes, osteoporosis, and dysmenorrhea were quickly developed and, later, methods of hormonal contraception. Sophisticated biochemical methods revealed the mechanisms of estrogen synthesis through the enzyme aromatase and, after discovery of the estrogen receptors, their specific biologic actions. Molecular techniques facilitated understanding of the specific transcriptional and translational events requiring estrogen. This body of knowledge led to methods to prevent and treat hormone-dependent neoplasms as well as a variety of other estrogen-related conditions. More recently, the role of estrogen in men was uncovered by prismatic examples of estrogen deficiency in male patients and by knockout of the estrogen receptor and aromatase in animals. As studies became more extensive, the effects of estrogen on nearly every organ were described. We conclude that the history of estrogen illustrates the role of intellectual reasoning, motivation, and serendipity in advancing knowledge about this important sex steroid.

Relationship Between Thyroid Hormone Levels and Mean Platelet Count and Volume: Quantitative Assessment

Background

The hormones of the hypophysis-thyroid axis (HTA), thyroid stimulating hormone (TSH), and thyroid hormones, L-thyroxine (T4) and 3, 3′, 5-L-triiodothyronine (T3), modulate the metabolism, differentiation, and proliferation of almost every cell in the body. Several studies have examined the effect of HTA hormones on platelet count and mean platelet volume (MPV), but have reported inconsistent results. Our aim was to examine the association between HTA hormones and platelet count and MPV in a large cohort of the adult population of the United States.

Methods 

We used the continuous National Health and Nutritional Examination Survey (NHANES) which made available data on HTA hormones (1999-2000, 2001-2002, 2007-2008, 2009-2010, and 2011-2012) to examine the association between HTA hormones and platelet count and MPV. Analyses were performed with adjustments for the complex survey sampling methods of NHANES data. Unadjusted and adjusted generalized linear regressions were performed to examine the relationship between HTA hormones and platelet count and MPV. Regression models were adjusted for age, sex, race, alcohol use, smoking status, serum c-reactive protein, red blood cell folate, diabetes mellitus, glomerular filtration rate, body mass index, and hypertension.

Results

Of the 10,619 individuals eligible for inclusion in the analyses, 5,267 (49.6%) were females and 2,132 (20.08%) were African Americans. The mean ± standard deviation of platelet count was 256.4 ± 67.1 10⁹/L, MPV 8.04 ± 0.92 fL, serum T4 7.92 ± 1.68 mg/dL, and serum T3 114.08 ± 24.6 ng/dL. In unadjusted analyses, an increase in the serum levels of T4 or T3 was associated with a significant increase in the platelet count and MPV (all p-values < 0.05). In contrast, an increase in serum TSH level was associated with a significant decrease in the platelet count (p-value = 0.05) but had no effect on MPV. After adjustment for potential confounders, serum T4 levels were significantly associated with platelet count but not with MPV. Individuals in the lowest quartile of T4 had 18.73 x 10⁹/L lower platelet count than individuals in the upper-most quartile (p-value = 0.03). Serum TSH and serum T3 levels had no effect on platelet count or MPV after adjusting for potential confounding variables.

Conclusions

We report that only serum T4 levels, and not TSH or T3 levels, are independently associated with platelet count and there is no independent association between HTA hormones and MPV. Our findings suggest a possible role of serum T4 on thrombopoiesis or on platelet lifespan.

Nuclear Receptor Nur77 Deficiency Alters Dendritic Cell Function

Dendritic cells (DCs) are the professional antigen-presenting cells of the immune system. Proper function of DCs is crucial to elicit an effective immune response against pathogens and to induce antitumor immunity. Different members of the nuclear receptor (NR) family of transcription factors have been reported to affect proper function of immune cells. Nur77 is a member of the NR4A subfamily of orphan NRs that is expressed and has a function within the immune system. We now show that Nur77 is expressed in different murine DCs subsets in vitro and ex vivo, in human monocyte-derived DCs (moDCs) and in freshly isolated human BDCA1⁺ DCs, but its expression is dispensable for DC development in the spleen and lymph nodes. We show, by siRNA-mediated knockdown of Nur77 in human moDCs and by using Nur77^-/- murine DCs, that Nur77-deficient DCs have enhanced inflammatory responses leading to increased T cell proliferation. Treatment of human moDCs with 6-mercaptopurine, an activator of Nur77, leads to diminished DC activation resulting in an impaired capacity to induce IFNγ production by allogeneic T cells. Altogether, our data show a yet unexplored role for Nur77 in modifying the activation status of murine and human DCs. Ultimately, targeting Nur77 may prove to be efficacious in boosting or diminishing the activation status of DCs and may lead to the development of improved DC-based immunotherapies in, respectively, cancer treatment or treatment of autoimmune diseases.

Thyroid Dysfunction and Anemia: A Prospective Cohort Study and a Systematic Review

BACKGROUND

Even though the association between thyroid dysfunction and anemia is commonly described, it is not known whether it is clinically relevant. This study set out to quantify the association of thyroid dysfunction on hemoglobin (Hb) concentration and risk of anemia. A systematic review (MEDLINE and EMBASE, from inception until May 15, 2017) was conducted to interpret the findings in context.

METHODS

Participants from the EPIC-Norfolk cohort with available baseline thyrotropin (TSH), free thyroxine (fT4), and Hb were included. Euthyroidism was defined as TSH 0.45-4.49 mIU/L (reference category), hypothyroidism as TSH ≥4.50 mIU/L (subclinical [SHypo] with normal fT4 or overt [OHypo] with low fT4), and hyperthyroidism as TSH ≤0.44 mIU/L (subclinical [SHyper] with normal fT4 or overt [OHyper] with elevated fT4). Anemia was defined as Hb <12 g/dL in women and Hb <13 g/dL in men. In the cross-sectional analyses, multiple linear regression was used to compare Hb across TSH categories. In the prospective analysis, participants with OHypo/OHyper at baseline were excluded, as it was assumed that they were treated for overt thyroid disease. A covariance model was used to determine change in Hb concentration from baseline to last follow-up, and multivariable Cox regression was used to analyze anemia risk.

RESULTS

In the cross-sectional population (n = 12,337), the adjusted Hb was 0.22 g/dL lower [confidence interval (CI) 0.07-0.38] in OHypo compared to euthyroids, and 0.08 g/dL lower [CI -0.23 to 0.38] in OHyper. In the prospective analysis, 460/7031 participants developed anemia over a median follow-up of 4.7 years. The adjusted mean Hb change over time was -0.04 g/dL in SHypo [CI -0.14 to 0.06] and 0.05 g/dL in SHyper [CI -0.10 to 0.20]. The adjusted hazard ratio for anemia was 0.99 [CI 0.67-1.48] in SHypo, and 0.52 [CI 0.23-1.16] in SHyper. The systematic review returned no other prospective studies on this association, but cross-sectional and case-control studies showed comparable results.

CONCLUSION

In this first prospective population-based cohort, subclinical thyroid dysfunction was not associated with a change in Hb concentration during follow-up and was not an independent risk factor for developing anemia; variations in Hb concentration in patients with overt thyroid dysfunction were not clinically relevant.

Genetic abnormalities associated with acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) occurs with high frequency in childhood and is associated with high mortality in adults. Recent technical advances in next‐generation sequencing have shed light on genetic abnormalities in hematopoietic stem/progenitor cells as the precursor to ALL pathogenesis. Based on these genetic abnormalities, ALL is now being reclassified into newly identified subtypes. Philadelphia chromosome‐like B‐lineage ALL is one of the new high‐risk subtypes characterized by genetic alterations that activate various signaling pathways, including those involving cytokine receptors, tyrosine kinases, and epigenetic modifiers. Philadelphia chromosome‐like ALL is essentially heterogeneous; however, deletion mutations in the IKZF1 gene encoding the transcription factor IKAROS underlie many cases as a key factor inducing aggressive phenotypes and poor treatment responses. Whole‐genome sequencing studies of ALL patients and ethnically matched controls also identified inherited genetic variations in lymphoid neoplasm‐related genes, which are likely to increase ALL susceptibility. These findings are directly relevant to clinical hematology, and further studies on this aspect could contribute to accurate diagnosis, effective monitoring of residual disease, and patient‐oriented therapies.

A high concentration of triiodothyronine attenuates the stimulatory effect on hemin-induced erythroid differentiation of human erythroleukemia K562 cells

Although thyroid hormone is a known stimulator of erythropoietic differentiation, severe anemia is sometimes observed in patients with hyperthyroidism and this mechanism is not fully understood. The aim of this study was to investigate the effect of triiodothyronine (T3) on hemin-induced erythropoiesis. Human erythroleukemia K562 cells were used as an erythroid differentiation model. Cell differentiation was induced by hemin and the effect of pre-incubation with T3 (0.1 to 100 nM) was analyzed by measuring the benzidine-positive rate, hemoglobin content, CD71 expression (transferrin receptor), and mRNA expression for transcription factors related to erythropoiesis and thyroid hormone receptors (TRs). Hemin, a promoter of erythroid differentiation, increased the levels of mRNAs for TRα, TRβ, and retinoid X receptor α (RXRα), as well as those for nuclear factor-erythroid 2 (NFE2), GATA-binding protein 1 (GATA1) and GATA-binding protein 2 (GATA2). Lower concentrations of T3 had a stimulatory effect on hemin-induced hemoglobin production (1 and 10 nM), CD71 expression (0.1 nM), and α-globin mRNA expression (1 nM), while a higher concentration of T3 (100 nM) abrogated the stimulatory effect on these parameters. T3 at 100 nM did not affect cell viability and proliferation, suggesting that the abrogation of erythropoiesis enhancement was not due to toxicity. T3 at 100 nM also significantly inhibited expression of GATA2 and RXRα mRNA, compared to 1 nM T3. We conclude that a high concentration of T3 attenuates the classical stimulatory effect on erythropoiesis exerted by a low concentration of T3 in hemin-induced K562 cells.

Oxymetholone therapy of fanconi anemia suppresses osteopontin transcription and induces hematopoietic stem cell cycling

Androgens are widely used for treating Fanconi anemia (FA) and other human bone marrow failure syndromes, but their mode of action remains incompletely understood. Aged Fancd2^−/− mice were used to assess the therapeutic efficacy of oxymetholone (OXM) and its mechanism of action. Eighteen-month-old Fancd2^−/− mice recapitulated key human FA phenotypes, including reduced bone marrow cellularity, red cell macrocytosis, and peripheral pancytopenia. As in humans, chronic OXM treatment significantly improved these hematological parameters and stimulated the proliferation of hematopoietic stem and progenitor cells. RNA-Seq analysis implicated downregulation of osteopontin as an important potential mechanism for the drug’s action. Consistent with the increased stem cell proliferation, competitive repopulation assays demonstrated that chronic OXM therapy eventually resulted in stem cell exhaustion. These results expand our knowledge of the regulation of hematopoietic stem cell proliferation and have direct clinical implications for the treatment of bone marrow failure.

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OXM treatment causes loss of quiescence and stem cell exhaustion

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RNaseq analysis reveals transcriptional changes in key pathways in Fancd2^−/− HSPC

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OXM suppresses transcription of osteopontin, a known stem cell quiescence promoter

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Unlike previous notions, OXM has no effect on telomerase expression or EPO signaling

Computational promoter modeling identifies the modes of transcriptional regulation in hematopoietic stem cells

Extrinsic and intrinsic regulators are responsible for the tight control of hematopoietic stem cells (HSCs), which differentiate into all blood cell lineages. To understand the fundamental basis of HSC biology, we focused on differentially expressed genes (DEGs) in long-term and short-term HSCs, which are closely related in terms of cell development but substantially differ in their stem cell capacity. To analyze the transcriptional regulation of the DEGs identified in the novel transcriptome profiles obtained by our RNA-seq analysis, we developed a computational method to model the linear relationship between gene expression and the features of putative regulatory elements. The transcriptional regulation modes characterized here suggest the importance of transcription factors (TFs) that are expressed at steady state or at low levels. Remarkably, we found that 24 differentially expressed TFs targeting 21 putative TF-binding sites contributed significantly to transcriptional regulation. These TFs tended to be modulated by other nondifferentially expressed TFs, suggesting that HSCs can achieve flexible and rapid responses via the control of nondifferentially expressed TFs through a highly complex regulatory network. Our novel transcriptome profiles and new method are powerful tools for studying the mechanistic basis of cell fate decisions.

Regulation of monocyte differentiation by specific signaling modules and associated transcription factor networks

Monocyte/macrophages are important players in orchestrating the immune response as well as connecting innate and adaptive immunity. Myelopoiesis and monopoiesis are characterized by the interplay between expansion of stem/progenitor cells and progression towards further developed (myelo)monocytic phenotypes. In response to a variety of differentiation-inducing stimuli, various prominent signaling pathways are activated. Subsequently, specific transcription factors are induced, regulating cell proliferation and maturation. This review article focuses on the integration of signaling modules and transcriptional networks involved in the determination of monocytic differentiation.

Retinoid X receptors in macrophage biology

Retinoid X receptors (RXRs) form a distinct and unique subclass within the nuclear receptor (NR) superfamily of ligand-dependent transcription factors. RXRs regulate a plethora of genetic programs, including cell differentiation, the immune response, and lipid and glucose metabolism. Recent advances reveal that RXRs are important regulators of macrophages, key players in inflammatory and metabolic disorders. This review outlines the versatility of RXR action in the control of macrophage gene transcription through its heterodimerization with other NRs or through RXR homodimerization. We also highlight the potential of RXR-controlled transcriptional programs as targets for the treatment of pathologies associated with altered macrophage function, such as atherosclerosis, insulin resistance, autoimmunity, and neurodegeneration.

Retinoic acid regulates the development of a gut-homing precursor for intestinal dendritic cells

The vitamin A metabolite retinoic acid (RA) regulates intestinal immune responses through immunomodulatory actions on intestinal dendritic cells (DCs) and lymphocytes. Here, we show that RA also controls the generation of gut-tropic migratory DC precursors, referred to as pre-mucosal DCs (pre-μDCs). Pre-μDCs express the gut trafficking receptor α4β7 and home preferentially to the intestines. They develop in the bone marrow (BM), can differentiate into CCR9⁺ plasmacytoid DCs as well as conventional DCs (cDCs), but preferentially give rise to CD103⁺ intestinal cDCs. Generation of pre-μDCs in vivo in the BM or in vitro is regulated by RA and RA receptor α (RARα) signaling. The frequency of pre-μDCs is reduced in vitamin A-deficient animals and in animals treated with RAR inhibitors. The results define a novel vitamin A-dependent, RA-regulated developmental sequence for DCs and identify a targeted precursor for CD103⁺ cDCs in the gut.

Expression of prion protein in mouse erythroid progenitors and differentiating murine erythroleukemia cells

Prion diseases have been observed to deregulate the transcription of erythroid genes, and prion protein knockout mice have demonstrated a diminished response to experimental anemia. To investigate the role of the cellular prion protein (PrP(C)) in erythropoiesis, we studied the protein's expression on mouse erythroid precursors in vivo and utilized an in vitro model of the erythroid differentiation of murine erythroleukemia cells (MEL) to evaluate the effect of silencing PrP(C) through RNA interference.The expression of PrP(C) and selected differentiation markers was analyzed by quantitative multicolor flow cytometry, western blot analysis and quantitative RT-PCR. The silencing of PrP(C) expression in MEL cells was achieved by expression of shRNAmir from an integrated retroviral vector genome. The initial upregulation of PrP(C) expression in differentiating erythroid precursors was detected both in vivo and in vitro, suggesting PrP(C)'s importance to the early stages of differentiation. The upregulation was highest on early erythroblasts (16200±3700 PrP(C) / cell) and was followed by the gradual decrease of PrP(C) level with the precursor's maturation reaching 470±230 PrP(C) / cell on most mature CD71(-)Ter119(+) small precursors. Interestingly, the downregulation of PrP(C) protein with maturation of MEL cells was not accompanied by the decrease of PrP mRNA. The stable expression of anti-Prnp shRNAmir in MEL cells led to the efficient (>80%) silencing of PrP(C) levels. Cell growth, viability, hemoglobin production and the transcription of selected differentiation markers were not affected by the downregulation of PrP(C).In conclusion, the regulation of PrP(C) expression in differentiating MEL cells mimics the pattern detected on mouse erythroid precursors in vivo. Decrease of PrP(C) protein expression during MEL cell maturation is not regulated on transcriptional level. The efficient silencing of PrP(C) levels, despite not affecting MEL cell differentiation, enables created MEL lines to be used for studies of PrP(C) cellular function.

Generation of ES cells for conditional expression of nuclear receptors and coregulators in vivo

Nuclear receptors and coregulators orchestrate diverse aspects of biological functions and inappropriate expression of these factors often associates with human diseases. The present study describes a conditional overexpression system consisting of a minigene located at the Rosa26 locus in the genome of mouse embryonic stem (ES) cells. Before activation, the minigene is silent due to a floxed STOP cassette inserted between the promoter and the transgene. Upon cre-mediated excision of the STOP cassette, the minigene constitutively expresses the tagged transgene driven by the ubiquitous CAGGS promoter. Thus, this system can be used to express target gene in any tissue in a spatial and/or temporal manner if respective cre mouse lines are available. Serving as proof of principle, the CAG-S-hCOUP-TFI allele was generated in ES cells and subsequently in mice. This allele was capable of conditionally overexpressing human chicken ovalbumin upstream promoter-transcription factor I (COUP-TFI) in all tissues tested upon activation by cre drivers. This allele was further subjected to address functionality of expressed COUP-TFI and the functional similarity between COUP-TFI and COUP-TFII. Expression of COUP-TFI in COUP-TFII-ablated uterus suppressed aberrant estrogen receptor-alpha activities and rescued implantation and decidualization defects of COUP-TFII mutants, suggesting that COUP-TFI and COUP-TFII are able to functionally compensate for each other in the uterus. A toolbox currently under construction will contain ES cell lines for overexpressing all 48 nuclear receptors and selected 10 coregulators. Upon completion, it will be a very valuable resource for the scientific community. Several ES cells are currently available for distribution.