Lysine-specific demethylase 1 is a therapeutic target for fetal hemoglobin induction

Omics Studies in Hemoglobinopathies

Hemoglobinopathies include all genetic diseases of hemoglobin and are grouped into thalassemia syndromes and structural hemoglobin variants. The β-thalassemias constitute a group of severe anemias with monogenic inheritance, caused by β-globin gene mutations. This review is focused on omics studies in hemoglobinopathies and mainly β-thalassemia, and discusses genomic, epigenomic, transcriptomic, proteomic and metabolomic findings. Omics analyses have identified various disease modifiers with an impact on disease severity and efficacy of treatments. These modifiers have contributed to the understanding of globin genes regulation/hemoglobin switching and the development of novel therapies. How omics data and their integration can contribute to efficient patient stratification, therapeutic management, improvements in existing treatments and application of novel personalized therapies is discussed.

Targeting sickle cell disease root-cause pathophysiology with small molecules

The complex, frequently devastating, multi-organ pathophysiology of sickle cell disease has a single root cause: polymerization of deoxygenated sickle hemoglobin. A logical approach to disease modification is, therefore, to interdict this root cause. Ideally, such interdiction would utilize small molecules that are practical and accessible for worldwide application. Two types of such small molecule strategies are actively being evaluated in the clinic. The first strategy intends to shift red blood cell precursor hemoglobin manufacturing away from sickle hemoglobin and towards fetal hemoglobin, which inhibits sickle hemoglobin polymerization by a number of mechanisms. The second strategy intends to chemically modify sickle hemoglobin directly in order to inhibit its polymerization. Important lessons have been learnt from the pre-clinical and clinical evaluations to date. Open questions remain, but this review summarizes the valuable experience and knowledge already gained, which can guide ongoing and future efforts for molecular mechanism-based, practical and accessible disease modification of sickle cell disease.

Peptides as epigenetic modulators: therapeutic implications

Peptides originating from different sources (endogenous, food derived, environmental, and synthetic) are able to influence different aspects of epigenetic regulation. Endogenous short peptides, resulting from proteolytic cleavage of proteins or upon translation of non-annotated out of frame transcripts, can block DNA methylation and hereby regulate gene expression. Peptides entering the body by digestion of food-related proteins can modulate DNA methylation and/or histone acetylation while environmental peptides, synthesized by bacteria, fungi, and marine sponges, mainly inhibit histone deacetylation. In addition, synthetic peptides that reverse or inhibit different epigenetic modifications of both histones and the DNA can be developed as well. Next to these DNA and histone modifications, peptides can also influence the expression of non-coding RNAs such as lncRNAs and the maturation of miRNAs.

Seen the advantages over small molecules, the development of peptide therapeutics is an interesting approach to treat diseases with a strong epigenetic basis like cancer and Alzheimer’s disease. To date, only a limited number of drugs with a proven epigenetic mechanism of action have been approved by the FDA of which two (romidepsin and nesiritide) are peptides. A large knowledge gap concerning epigenetic effects of peptides is present, and this class of molecules deserves more attention in the development as epigenetic modulators. In addition, none of the currently approved peptide drugs are under investigation for their potential effects on epigenetics, hampering drug repositioning of these peptides to other indications with an epigenetic etiology.

Conjugate prodrug AN-233 induces fetal hemoglobin expression in sickle erythroid progenitors and β-YAC transgenic mice

Pharmacologic induction of fetal hemoglobin (HbF) is an effective strategy for treating sickle cell disease (SCD) by ameliorating disease severity. Hydroxyurea is the only FDA-approved agent that induces HbF, but significant non-responders and requirement for frequent monitoring of blood counts for drug toxicity limit clinical usefulness. Therefore, we investigated a novel prodrug conjugate of butyric acid (BA) and δ-aminolevulinate (ALA) as a potential HbF inducing agent, using erythroid precursors and a preclinical β-YAC mouse model. We observed significantly increased γ-globin gene transcription and HbF expression mediated by AN-233 in K562 cells. Moreover, AN-233 stimulated mild heme biosynthesis and inhibited expression of heme-regulated eIF2α kinase involved in silencing γ-globin expression. Studies using primary erythroid precursors generated from sickle peripheral blood mononuclear cells verified the ability of AN-233 to induce HbF, increase histone H3 and H4 acetylation levels at the γ-globin promoter and reduce erythroid precursor sickling by 50%. Subsequent drug treatment of β-YAC transgenic mice confirmed HbF induction in vivo by AN-233 through an increase in the percentage of HbF positive red blood cells and HbF levels measured by flow cytometry. These data support the potential development of AN-233 for the treatment of SCD.

Thiourea derivatives induce fetal hemoglobin production in-vitro: A new class of potential therapeutic agents for β-thalassemia

Fetal hemoglobin (HbF) induction is a cost-effective therapeutic approach for the treatment of β-hemoglobinopathies like β-thalassemia and sickle cell anemia. The present study discusses the potential of thiourea derivatives as new class of compounds that induce the fetal hemoglobin production. HbF inducing effect of thiourea derivatives was studied using experimental cell system, the human erythroleukemic K562 cell line. Erythroid induction of K562 cells was studied by the benzidine/H₂O₂ reaction, total hemoglobin production was estimated by plasma hemoglobin assay kit, and γ-globin gene expression by RT-qPCR, whereas fetal hemoglobin production was estimated by flow cytometry and immunofluorescence microscopy. The results indicated that newly synthesized thiourea derivative are potent inducers of erythroid differentiation of K562 cells with an increased γ-globin gene expression and fetal hemoglobin production. Moreover, these compounds showed no cytotoxic effect and inhibition on K562 cells at HbF inducing concentrations. It is important to note that hydroxyurea is a cytotoxic chemotherapeutic agent and have deleterious side effects, reflecting the need to identify new safe and effective HbF induces. These results signify thiourea derivatives as promising HbF inducers, with the potential to be studied against hematological disorders, including β-thalassemia and sickle cell anemia.

Phthalides serve as potent modulators to boost fetal hemoglobin induction therapy for β-hemoglobinopathies

Fetal hemoglobin (HbF) induction therapy has become the most promising strategy for treating β-hemoglobinopathies, including sickle-cell diseases and β-thalassemia. However, subtle but critical structural difference exists between HbF and normal adult hemoglobin (HbA), which inevitably leads to reduced binding of the endogenous modulator 2,3-bisphosphoglycerate (2,3-BPG) to HbF and thus increased oxygen affinity and decreased oxygen transport efficiency of HbF. We combined the oxygen equilibrium experiments, resonance Raman (RR) spectroscopy, and molecular docking modeling, and we discuss 2 phthalides, z-butylidenephthalide and z-ligustilide, that can effectively lower the oxygen affinity of HbF. They adjust it to a level closer to that of HbA and make it a more satisfactory oxygen carrier for adults. From the oxygen equilibrium curve measurements, we show that the 2 phthalides are more effective than 2,3-BPG for modulating HbF. The RR spectra show that phthalides allosterically stabilize the oxygenated HbF in the low oxygen affinity conformation, and the molecular docking modeling reveals that the 2 chosen phthalides interact with HbF via the cleft around the γ1/γ2 interface with a binding strength ∼1.6 times stronger than that of 2,3-BPG. We discuss the implications of z-butylidenephthalide and z-ligustilide in boosting the efficacy of HbF induction therapy to mitigate the clinical severities of β-hemoglobinopathies.

Therapeutic strategies for sickle cell disease: towards a multi-agent approach

For over 100 years, clinicians and scientists have been unravelling the consequences of the A to T substitution in the β-globin gene that produces haemoglobin S, which leads to the systemic manifestations of sickle cell disease (SCD), including vaso-occlusion, anaemia, haemolysis, organ injury and pain. However, despite growing understanding of the mechanisms of haemoglobin S polymerization and its effects on red blood cells, only two therapies for SCD - hydroxyurea and L-glutamine - are approved by the US Food and Drug Administration. Moreover, these treatment options do not fully address the manifestations of SCD, which arise from a complex network of interdependent pathophysiological processes. In this article, we review efforts to develop new drugs targeting these processes, including agents that reactivate fetal haemoglobin, anti-sickling agents, anti-adhesion agents, modulators of ischaemia-reperfusion and oxidative stress, agents that counteract free haemoglobin and haem, anti-inflammatory agents, anti-thrombotic agents and anti-platelet agents. We also discuss gene therapy, which holds promise of a cure, although its widespread application is currently limited by technical challenges and the expense of treatment. We thus propose that developing systems-oriented multi-agent strategies on the basis of SCD pathophysiology is needed to improve the quality of life and survival of people with SCD.

Toxoplasma gondii in Captive Wild Felids of Mexico: Its Frequency and Capability to Eliminate Oocysts

There is little information about Toxoplasma gondii in wild felids, even when these species have been associated with cases of toxoplasmosis in humans. In this study, samples of serum and whole blood were collected from 42 felids from 10 different species, in 4 Mexican zoos. Stool samples from 36 animals were also collected, corresponding to 82% of the felids included in the study. Stool samples were used for the search of oocysts by light field microscopy and PCR. Serum samples were analyzed by indirect immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody test (IFAT). DNA samples were purified from whole blood and stool for the amplification of a fragment of the SAG1 gene of T. gondii by a nested PCR (nPCR). The seroprevalence of IgG anti-T. gondii-specific antibodies by means of the ELISA was 100% (42/42) and 52.4% (22/42) by IFAT. The titers obtained varied from 1:80 to 1:2560. DNA of T. gondii was detected in 9.5% (4/42) of the blood samples by using nPCR. No oocysts were observed in the stool samples analyzed by light field microscopy. However, the DNA of the parasite was identified in 14.3% (5/35) of the stool samples evaluated. These results indicate a high prevalence of T. gondii in the studied populations of wild felids in captivity, with evidence of parasitemia and elimination of few oocysts even in adult hosts.

BAP1 regulation of the key adaptor protein NCoR1 is critical for γ-globin gene repression

Human globin gene production transcriptionally "switches" from fetal to adult synthesis shortly after birth and is controlled by macromolecular complexes that enhance or suppress transcription by cis elements scattered throughout the locus. The DRED (direct repeat erythroid-definitive) repressor is recruited to the ε-globin and γ-globin promoters by the orphan nuclear receptors TR2 (NR2C1) and TR4 (NR2C2) to engender their silencing in adult erythroid cells. Here we found that nuclear receptor corepressor-1 (NCoR1) is a critical component of DRED that acts as a scaffold to unite the DNA-binding and epigenetic enzyme components (e.g., DNA methyltransferase 1 [DNMT1] and lysine-specific demethylase 1 [LSD1]) that elicit DRED function. We also describe a potent new regulator of γ-globin repression: The deubiquitinase BRCA1-associated protein-1 (BAP1) is a component of the repressor complex whose activity maintains NCoR1 at sites in the β-globin locus, and BAP1 inhibition in erythroid cells massively induces γ-globin synthesis. These data provide new mechanistic insights through the discovery of novel epigenetic enzymes that mediate γ-globin gene repression.

Long non-coding RNA-dependent mechanism to regulate heme biosynthesis and erythrocyte development

In addition to serving as a prosthetic group for enzymes and a hemoglobin structural component, heme is a crucial homeostatic regulator of erythroid cell development and function. While lncRNAs modulate diverse physiological and pathological cellular processes, their involvement in heme-dependent mechanisms is largely unexplored. In this study, we elucidated a lncRNA (UCA1)-mediated mechanism that regulates heme metabolism in human erythroid cells. We discovered that UCA1 expression is dynamically regulated during human erythroid maturation, with a maximal expression in proerythroblasts. UCA1 depletion predominantly impairs heme biosynthesis and arrests erythroid differentiation at the proerythroblast stage. Mechanistic analysis revealed that UCA1 physically interacts with the RNA-binding protein PTBP1, and UCA1 functions as an RNA scaffold to recruit PTBP1 to ALAS2 mRNA, which stabilizes ALAS2 mRNA. These results define a lncRNA-mediated posttranscriptional mechanism that provides a new dimension into how the fundamental heme biosynthetic process is regulated as a determinant of erythrocyte development.

LncRNAs modulate diverse physiological cellular processes, however, their involvement in heme-dependent processes are not yet clear. Here the authors reveal the role of lncRNA UCA1 in erythroid cell development.

Drug Design Concepts for LSD1-Selective Inhibitors

Lysine-specific demethylase 1 (LSD1) is one of the flavin-dependent oxidases and is involved in many cellular processes by controlling the methylation of histone H3. Recently, it has been reported that LSD1 is associated with several diseases such as cancer, metabolic disorders, and psychiatric diseases. Thus, LSD1 is an attractive molecular target for the treatment of these diseases, and its inhibitors are predicted as therapeutic agents. Although a variety of LSD1 inhibitors have been reported to date, many of them show insufficient activities and selectivity toward LSD1. Meanwhile, we identified several LSD1-selective inhibitors using target-guided synthesis strategies based on our original ideas. Our LSD1 inhibitors show not only potent LSD1-selective inhibitory activities, but also unique bioactivities both in vitro and in vivo. This account highlights our drug design concepts for and identification of LSD1-selective inhibitors.

Oral administration of the LSD1 inhibitor ORY-3001 increases fetal hemoglobin in sickle cell mice and baboons

Increased levels of fetal hemoglobin (HbF) lessen the severity of symptoms and increase the life span of patients with sickle cell disease (SCD). More effective strategies to increase HbF are needed because the current standard of care, hydroxyurea, is not effective in a significant proportion of patients. Treatment of the millions of patients projected worldwide would best be accomplished with an orally administered drug therapy that increased HbF. LSD1 is a component of corepressor complexes that repress γ-globin gene expression and are a therapeutic target for HbF reactivation. We have shown that subcutaneous administration of RN-1, a pharmacological LSD1 inhibitor, increased γ-globin expression in SCD mice and baboons, which are widely acknowledged as the best animal model in which to test the activity of HbF-inducing drugs. The objective of this investigation was to test the effect of oral administration of a new LSD1 inhibitor, ORY-3001. Oral administration of ORY-3001 to SCD mice (n = 3 groups) increased γ-globin expression, Fetal Hemoglobin (HbF)-containing (F) cells, and F reticulocytes (retics). In normal baboons (n = 7 experiments) treated with ORY-3001, increased F retics, γ-globin chain synthesis, and γ-globin mRNA were observed. Experiments in anemic baboons (n = 2) showed that ORY-3001 increased F retics (PA8695, predose = 24%, postdose = 66.8%; PA8698: predose = 13%, postdose = 93.6%), γ-globin chain synthesis (PA8695: predose = 0.07 γ/γ+β, postdose = 0.20 γ/γ+β; PA8698: predose = 0.02 γ/γ+β, postdose = 0.44 γ/γ+β), and γ-globin mRNA (PA8695: predose = 0.06 γ/γ+β, postdose = 0.18 γ/γ+β; PA8698: predose = 0.03 γ/γ+β, postdose = 0.33 γ/γ+β). We conclude that oral administration of ORY-3001 increases F retics, γ-globin chain synthesis, and γ-globin mRNA in baboons and SCD mice, supporting further efforts toward the development of this drug for SCD therapy.

Inhibition of the histone demethylase KDM4B leads to activation of KDM1A, attenuates bacterial-induced pro-inflammatory cytokine release, and reduces osteoclastogenesis

Periodontal disease (PD) afflicts 46% of Americans with no effective adjunctive therapies available. While most pharmacotherapy for PD targets bacteria, the host immune response is responsible for driving tissue damage and bone loss in severe disease. Herein, we establish that the histone demethylase KDM4B is a potential drug target for the treatment of PD. Immunohistochemical staining of diseased periodontal epithelium revealed an increased abundance of KDM4B that correlates with inflammation. In murine calvarial sections exposed to Aggregatibacter actinomycetemcomitans lipopolysaccharide (Aa-LPS), immunohistochemical staining revealed a significant increase in KDM4B protein expression. The 8-hydroxyquinoline ML324 is known to inhibit the related demethylase KDM4E in vitro, but has not been evaluated against any other targets. Our studies indicate that ML324 also inhibits KDM4B (IC50: 4.9 μM), and decreases the pro-inflammatory cytokine response to an Aa-LPS challenge in vitro. Our results suggest that KDM4B inhibition-induced immunosuppression works indirectly, requiring new protein synthesis. In addition, fluorescence-stained macrophages exhibited a significant decrease in global monomethyl histone 3 lysine 4 (H3K4me) levels following an Aa-LPS challenge that was prevented by KDM4B inhibition, suggesting this effect is produced through KDM1A-mediated demethylation of H3K4. Finally, ML324 inhibition of KDM4B in osteoclast progenitors produced a significant reduction in Aa-LPS-induced osteoclastogenesis. These data link histone methylation with host immune response to bacterial pathogens in PD, and suggest a previously unreported, alternative mechanism for epigenetic control of the host inflammatory environment. As such, KDM4B represents a new therapeutic target for treating hyper-inflammatory diseases that result in bone destruction.

Potential role of LSD1 inhibitors in the treatment of sickle cell disease: a review of preclinical animal model data

Sickle cell disease (SCD) is caused by a mutation of the β-globin gene (Ingram VM. Nature 180: 326-328, 1957), which triggers the polymerization of deoxygenated sickle hemoglobin (HbS). Approximately 100,000 SCD patients in the United States and millions worldwide (Piel FB, et al. PLoS Med 10: e1001484, 2013) suffer from chronic hemolytic anemia, painful crises, multisystem organ damage, and reduced life expectancy (Rees DC, et al. Lancet 376: 2018-2031, 2010; Serjeant GR. Cold Spring Harb Perspect Med 3: a011783, 2013). Hematopoietic stem cell transplantation can be curative, but the majority of patients do not have a suitable donor (Talano JA, Cairo MS. Eur J Haematol 94: 391-399, 2015). Advanced gene-editing technologies also offer the possibility of a cure (Goodman MA, Malik P. Ther Adv Hematol 7: 302-315, 2016; Lettre G, Bauer DE. Lancet 387: 2554-2564, 2016), but the likelihood that these strategies can be mobilized to treat the large numbers of patients residing in developing countries is remote. A pharmacological treatment to increase fetal hemoglobin (HbF) as a therapy for SCD has been a long-sought goal, because increased levels of HbF (α₂γ₂) inhibit the polymerization of HbS (Poillin WN, et al. Proc Natl Acad Sci USA 90: 5039-5043, 1993; Sunshine HR, et al. J Mol Biol 133: 435-467, 1979) and are associated with reduced symptoms and increased lifespan of SCD patients (Platt OS, et al. N Engl J Med 330: 1639-1644, 1994; Platt OS, et al. N Engl J Med 325: 11-16, 1991). Only two drugs, hydroxyurea and l-glutamine, are approved by the US Food and Drug Administration for treatment of SCD. Hydroxyurea is ineffective at HbF induction in ~50% of patients (Charache S, et al. N Engl J Med 332: 1317-1322, 1995). While polymerization of HbS has been traditionally considered the driving force in the hemolysis of SCD, the excessive reactive oxygen species generated from red blood cells, with further amplification by intravascular hemolysis, also are a major contributor to SCD pathology. This review highlights a new class of drugs, lysine-specific demethylase (LSD1) inhibitors, that induce HbF and reduce reactive oxygen species.

Modelling human haemoglobin switching

Genetic lesions of the β-globin gene result in haemoglobinopathies such as β-thalassemia and sickle cell disease. To discover and test new molecular medicines for β-haemoglobinopathies, cell-based and animal models are now being widely utilised. However, multiple in vitro and in vivo models are required due to the complex structure and regulatory mechanisms of the human globin gene locus, subtle species-specific differences in blood cell development, and the influence of epigenetic factors. Advances in genome sequencing, gene editing, and precision medicine have enabled the first generation of molecular therapies aimed at reactivating, repairing, or replacing silenced or damaged globin genes. Here we compare and contrast current animal and cell-based models, highlighting their complementary strengths, reflecting on how they have informed the scope and direction of the field, and describing some of the novel molecular and precision medicines currently under development or in clinical trial.

Design, Synthesis, and In Vitro Evaluation of Novel Histone H3 Peptide-Based LSD1 Inactivators Incorporating α,α-Disubstituted Amino Acids with γ-Turn-Inducing Structures

Lysine-specific demethylase 1 (LSD1) mainly removes methyl groups of mono- or di-methylated lysine residues at the fourth position of histone H3 to epigenetically regulate the expression of genes associated with several diseases, such as cancer. Therefore, LSD1 inactivators are expected to be used as therapeutic agents. In this study, to identify novel peptide-based LSD1 inactivators, we focused on the X-ray structure of LSD1 complexed with a H3 peptide-based suicide substrate. It has been proposed that a methylated histone substrate forms three consecutive γ-turn structures in the active pocket of LSD1. Based on this, we designed and synthesized novel histone H3 peptide-based LSD1 inactivators 2a⁻c by incorporating various α,α-disubstituted amino acids with γ-turn-inducing structures. Among synthetic peptides 2a⁻c, peptide 2b incorporating two 1-aminocyclohexanecarboxylic acids at both sides of a lysine residue bearing a trans-2-phenylcyclopropylamine (PCPA) moiety, which is a pharmacophore for LSD1 inactivation, was the most potent and selective LSD1 inactivator. These findings are useful for the further development of histone H3 peptide-based LSD1 inactivators.

Evolution of hemoglobin loci and their regulatory elements

Across the expanse of vertebrate evolution, each species produces multiple forms of hemoglobin in erythroid cells at appropriate times and in the proper amounts. The multiple hemoglobins are encoded in two globin gene clusters in almost all species. One globin gene cluster, linked to the gene NPRL3, is preserved in all vertebrates, including a gene cluster encoding the highly divergent globins from jawless vertebrates. This preservation of synteny may reflect the presence of a powerful enhancer of globin gene expression in the NPRL3 gene. Despite substantial divergence in noncoding DNA sequences among mammals, several epigenetic features of the globin gene regulatory regions are preserved across vertebrates. The preserved features include multiple DNase hypersensitive sites, at least one of which is an enhancer, and binding by key lineage-restricted transcription factors such as GATA1 and TAL1, which in turn recruit coactivators such as P300 that catalyze acetylation of histones. The maps of epigenetic features are strongly correlated with activity in gene regulation, and resources for accessing and visualizing such maps are readily available to the community of researchers and students.

Histone demethylase LSD1 regulates bone mass by controlling WNT7B and BMP2 signaling in osteoblasts

Multiple regulatory mechanisms control osteoblast differentiation and function to ensure unperturbed skeletal formation and remodeling. In this study we identify histone lysine-specific demethylase 1(LSD1/KDM1A) as a key epigenetic regulator of osteoblast differentiation. Knockdown of LSD1 promoted osteoblast differentiation of human mesenchymal stem cells (hMSCs) in vitro and mice lacking LSD1 in mesenchymal cells displayed increased bone mass secondary to accelerated osteoblast differentiation. Mechanistic in vitro studies revealed that LSD1 epigenetically regulates the expression of WNT7B and BMP2. LSD1 deficiency resulted in increased BMP2 and WNT7B expression in osteoblasts and enhanced bone formation, while downregulation of WNT7B- and BMP2-related signaling using genetic mouse model or small-molecule inhibitors attenuated bone phenotype in vivo. Furthermore, the LSD1 inhibitor tranylcypromine (TCP) could increase bone mass in mice. These data identify LSD1 as a novel regulator of osteoblast activity and suggest LSD1 inhibition as a potential therapeutic target for treatment of osteoporosis.

Fetal Hemoglobin Induction by Epigenetic Drugs

Fetal hemoglobin (HbF) inhibits the root cause of sickle pathophysiology, sickle hemoglobin polymerization. Individuals who naturally express high levels of HbF beyond infancy thus receive some protection from sickle complications. To mimic this natural genetic experiment using drugs, one guiding observation was that HbF is increased during recovery of bone marrow from extreme stress. This led to evaluation and approval of the cytotoxic (cell killing) drug hydroxyurea to treat sickle cell disease. Cytotoxic approaches are limited in potency and sustainability, however, since they require hematopoietic reserves sufficient to repeatedly mount recoveries from stress that destroys their counterparts, and such reserves are finite. HbF induction even by stress ultimately involves chromatin remodeling of the gene for HbF (HBG), therefore, a logical alternative approach is to directly inhibit epigenetic enzymes that repress HBG-implicated enzymes include DNA methyltransferase 1, histone deacetylases, lysine demethylase 1, protein arginine methyltransferase 5, euchromatic histone lysine methyltransferase 2 and chromodomain helicase DNA-binding protein 4. Clinical proof-of-principle that this alternative, noncytotoxic approach can generate substantial HbF and total hemoglobin increases has already been generated. Thus, with continued careful attention to fundamental biological and pharmacologic considerations (reviewed herein), there is potential that rational, molecular-targeted, safe and highly potent disease-modifying therapy can be realized for patients with sickle cell disease, with the accessibility and cost-effective properties needed for world-wide effect.

Pharmacological and molecular approaches for the treatment of β-hemoglobin disorders

β-hemoglobin disorders, such as β-thalassemia and sickle cell anemia are among the most prevalent inherited genetic disorders worldwide. These disorders are caused by mutations in the gene encoding hemoglobin-β (HBB), a vital protein found in red blood cells (RBCs) that carries oxygen from lungs to all parts of the human body. As a consequence, there has been an enduring interest in this field in formulating therapeutic strategies for the treatment of these diseases. Currently, there is no cure available for hemoglobin disorders, although, some patients have been treated with bone marrow transplantation, whose scope is limited because of the difficulty in finding a histocompatible donor and also due to transplant-associated clinical complications that can arise during the treatment. On account of these constraints, reactivation of fetal hemoglobin (HbF) synthesis holds immense promise and is a viable strategy to alleviate the symptoms of β-hemoglobin disorders. Development of new genomic tools has led to the identification of important natural genetic modifiers of hemoglobin switching which include BCL11A, KLF1, HBSIL-MYB, LRF, LSD1, LDB1, histone deacetylases 1 and 2 (HDAC1 and HDAC2). miRNAs are also promising therapeutic targets for development of more effective strategies for the induction of HbF production. Many new small molecule pharmacological inducers of HbF production are already under pre-clinical and clinical development. Furthermore, recent advancements in gene and cell therapy includes targeted genome editing and iPS cell technologies, both of which utilizes a patient's own cells, are emerging as extremely promising approaches for significantly reducing the burden of β-hemoglobin disorders.

Epigenetic Regulatory Mechanisms Induced by Resveratrol

Resveratrol (RVT) is one of the main natural compounds studied worldwide due to its potential therapeutic use in the treatment of many diseases, including cancer, diabetes, cardiovascular diseases, neurodegenerative diseases and metabolic disorders. Nevertheless, the mechanism of action of RVT in all of these conditions is not completely understood, as it can modify not only biochemical pathways but also epigenetic mechanisms. In this paper, we analyze the biological activities exhibited by RVT with a focus on the epigenetic mechanisms, especially those related to DNA methyltransferase (DNMT), histone deacetylase (HDAC) and lysine-specific demethylase-1 (LSD1).

SIRT1 activates the expression of fetal hemoglobin genes

High fetal hemoglobin (HbF, α₂ γ₂ ) levels ameliorate the clinical manifestations of sickle cell disease and β thalassemia. The mechanisms that repress HbF expression and silence γ-globin genes in adults are incompletely characterized and only a single HbF inducer, hydroxyurea, is approved for treatment, and only in patients with sickle cell disease. We identified SIRT1, a protein deacetylase, as a new inducer of γ-globin. SIRT1 knockdown decreased, while SIRT1 ectopic expression upregulated γ-globin gene (HBG) expression in primary human erythroid cells and in K562 cells. The small molecule SIRT1 activators SRT2104 and SRT1720 enhanced HBG expression in cord blood human erythroblasts and reactivated silenced HBG in adult human erythroblasts. Furthermore, SIRT1 binds in the β-globin gene cluster locus control region (LCR) and HBG promoters, promotes the looping of the LCR to HBG promoter, and increases the binding of RNA polymerase II and H4K16Ac in the HBG promoter. SIRT1 suppressed the expression of the HBG suppressors BCL11A, KLF1, HDAC1 and HDAC2. Lastly, SIRT1 did not change the proliferation of human erythroid progenitor cells or the expression of differentiation marker CD235a. These data suggest that SIRT1 activates HBG expression through facilitating LCR looping to the HBG promoter, inhibiting the expression of transcriptional suppressors of HBG, and indirectly increasing histone acetylation in the HBG promoter. SIRT1 is a potential therapeutic target for γ-globin gene induction, and small molecule SIRT1 activators might serve as a lead compound for the development of new HbF inducers.

The orphan nuclear receptor TR4 regulates erythroid cell proliferation and maturation

The orphan nuclear receptors TR4 (NR2C2) and TR2 (NR2C1) are the DNA-binding subunits of the macromolecular complex, direct repeat erythroid-definitive, which has been shown to repress ε- and γ-globin transcription during adult definitive erythropoiesis. Previous studies implied that TR2 and TR4 act largely in a redundant manner during erythroid differentiation; however, during the course of routine genetic studies, we observed multiple variably penetrant phenotypes in the Tr4 mutants, suggesting that indirect effects of the mutation might be masked by multiple modifying genes. To test this hypothesis, Tr4^+/- mutant mice were bred into a congenic C57BL/6 background and their phenotypes were reexamined. Surprisingly, we found that homozygous Tr4 null mutant mice expired early during embryogenesis, around embryonic day 7.0, and well before erythropoiesis commences. We further found that Tr4^+/- erythroid cells failed to fully differentiate and exhibited diminished proliferative capacity. Analysis of Tr4^+/- mutant erythroid cells revealed that reduced TR4 abundance resulted in decreased expression of genes required for heme biosynthesis and erythroid differentiation (Alad and Alas2), but led to significantly increased expression of the proliferation inhibitory factor, cyclin dependent kinase inhibitor (Cdkn1c) These studies support a vital role for TR4 in promoting erythroid maturation and proliferation, and demonstrate that TR4 and TR2 execute distinct, individual functions during embryogenesis and erythroid differentiation.

Editing an α-globin enhancer in primary human hematopoietic stem cells as a treatment for β-thalassemia

β-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and β-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with β-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with β-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for β-thalassemia.

β-thalassemia is characterised by the presence of an excess of α-globin chains, which contribute to erythrocyte pathology. Here the authors use CRISP/Cas9 to reduce α-globin expression in hematopoietic precursors, and show effectiveness in xenograft assays in mice.

Chemical probes targeting epigenetic proteins: Applications beyond oncology

Epigenetic chemical probes are potent, cell-active, small molecule inhibitors or antagonists of specific domains in a protein; they have been indispensable for studying bromodomains and protein methyltransferases. The Structural Genomics Consortium (SGC), comprising scientists from academic and pharmaceutical laboratories, has generated most of the current epigenetic chemical probes. Moreover, the SGC has shared about 4 thousand aliquots of these probes, which have been used primarily for phenotypic profiling or to validate targets in cell lines or primary patient samples cultured in vitro. Epigenetic chemical probes have been critical tools in oncology research and have uncovered mechanistic insights into well-established targets, as well as identify new therapeutic starting points. Indeed, the literature primarily links epigenetic proteins to oncology, but applications in inflammation, viral, metabolic and neurodegenerative diseases are now being reported. We summarize the literature of these emerging applications and provide examples where existing probes might be used.

Cellular analysis of the action of epigenetic drugs and probes

Small molecule drugs and probes are important tools in drug discovery, pharmacology, and cell biology. This is of course also true for epigenetic inhibitors. Important examples for the use of established epigenetic inhibitors are the study of the mechanistic role of a certain target in a cellular setting or the modulation of a certain phenotype in an approach that aims toward therapeutic application. Alternatively, cellular testing may aim at the validation of a new epigenetic inhibitor in drug discovery approaches. Cellular and eventually animal models provide powerful tools for these different approaches but certain caveats have to be recognized and taken into account. This involves both the selectivity of the pharmacological tool as well as the specificity and the robustness of the cellular system. In this article, we present an overview of different methods that are used to profile and screen for epigenetic agents and comment on their limitations. We describe not only diverse successful case studies of screening approaches using different assay formats, but also some problematic cases, critically discussing selected applications of these systems.

Fetal hemoglobin regulation in β-thalassemia: heterogeneity, modifiers and therapeutic approaches

INTRODUCTION

Stress erythropoiesis induces fetal hemoglobin (HbF) expression in β-thalassemias, however the level of expression is highly variable. The last decade has seen dramatic advances in our understanding of the molecular regulators of HbF production and the genetic factors associated with HbF levels, leading to the promise of new methods of the clinical induction of HbF. Areas covered: This article will review the heterogeneity and genetic modifiers of HbF and HbF induction therapy in β-thalassemia. Expert commentary: One promising curative β-thalassemia therapy is to induce HbF synthesis in β-thalassemic erythrocytes to therapeutic levels before clinical symptom occurs. Further understanding of HbF level variation and regulation is needed in order to predict the response from HbF-inducing approaches.

Animal models of β-hemoglobinopathies: utility and limitations

The structural and functional conservation of hemoglobin throughout mammals has made the laboratory mouse an exceptionally useful organism in which to study both the protein and the individual globin genes. Early researchers looked to the globin genes as an excellent model in which to examine gene regulation – bountifully expressed and displaying a remarkably consistent pattern of developmental activation and silencing. In parallel with the growth of research into expression of the globin genes, mutations within the β-globin gene were identified as the cause of the β-hemoglobinopathies such as sickle cell disease and β-thalassemia. These lines of enquiry stimulated the development of transgenic mouse models, first carrying individual human globin genes and then substantial human genomic fragments incorporating the multigenic human β-globin locus and regulatory elements. Finally, mice were devised carrying mutant human β-globin loci on genetic backgrounds deficient in the native mouse globins, resulting in phenotypes of sickle cell disease or β-thalassemia. These years of work have generated a group of model animals that display many features of the β-hemoglobinopathies and provided enormous insight into the mechanisms of gene regulation. Substantive differences in the expression of human and mouse globins during development have also come to light, revealing the limitations of the mouse model, but also providing opportunities to further explore the mechanisms of globin gene regulation. In addition, animal models of β-hemoglobinopathies have demonstrated the feasibility of gene therapy for these conditions, now showing success in human clinical trials. Such models remain in use to dissect the molecular events of globin gene regulation and to identify novel treatments based upon the reactivation of developmentally silenced γ-globin. Here, we describe the development of animal models to investigate globin switching and the β-hemoglobinopathies, a field that has paralleled the emergence of modern molecular biology and clinical genetics.

Activation of Fetal γ-globin Gene Expression via Direct Protein Delivery of Synthetic Zinc-finger DNA-Binding Domains

Reactivation of γ-globin expression has been shown to ameliorate disease phenotypes associated with mutations in the adult β-globin gene, including sickle cell disease. Specific mutations in the promoter of the γ-globin genes are known to prevent repression of the genes in the adult and thus lead to hereditary persistence of fetal hemoglobin. One such hereditary persistence of fetal hemoglobin is associated with a sequence located 567 bp upstream of the Gγ-globin gene which assembles a GATA-containing repressor complex. We generated two synthetic zinc-finger DNA-binding domains (ZF-DBDs) targeting this sequence. The -567Gγ ZF-DBDs associated with high affinity and specificity with the target site in the γ-globin gene promoter. We delivered the -567Gγ ZF-DBDs directly to primary erythroid cells. Exposure of these cells to the recombinant -567Gγ ZF-DBDs led to increased expression of the γ-globin gene. Direct protein delivery of ZF-DBDs that compete with transcription regulatory proteins will have broad implications for modulating gene expression in analytical or therapeutic settings.

Intron 1 GATA site enhances ALAS2 expression indispensably during erythroid differentiation

The first intronic mutations in the intron 1 GATA site (int-1-GATA) of 5-aminolevulinate synthase 2 (ALAS2) have been identified in X-linked sideroblastic anemia (XLSA) pedigrees, strongly suggesting it could be causal mutations of XLSA. However, the function of this int-1-GATA site during in vivo development remains largely unknown. Here, we generated mice lacking a 13 bp fragment, including this int-1-GATA site (TAGATAAAGCCCC) and found that hemizygous deletion led to an embryonic lethal phenotype due to severe anemia resulting from a lack of ALAS2 expression, indicating that this non-coding sequence is indispensable for ALAS2 expression in vivo. Further analyses revealed that this int-1-GATA site anchored the GATA site in intron 8 (int-8-GATA) and the proximal promoter, forming a long-range loop to enhance ALAS2 expression by an enhancer complex including GATA1, TAL1, LMO2, LDB1 and Pol II at least, in erythroid cells. However, compared with the int-8-GATA site, the int-1-GATA site is more essential for regulating ALAS2 expression through CRISPR/Cas9-mediated site-specific deletion. Therefore, the int-1-GATA site could serve as a valuable site for diagnosing XLSA in cases with unknown mutations.

Overexpression of Lysine-Specific Demethylase 1 Is Associated With Tumor Progression and Unfavorable Prognosis in Chinese Patients With Endometrioid Endometrial Adenocarcinoma

OBJECTIVE

Lysine-specific demethylase 1 (LSD1) is a kind of flavin adenine dinucleotide-dependent amine oxidase that regulates normal cellular differentiation, gene activation, tumorigenesis, and progression. This study aims to detect the expression level of LSD1 in endometrial cancer and to explore its role in the progression and prognosis of endometrioid endometrial adenocarcinoma (EEA).

METHODS

Immunohistochemistry was used to examine the expression of LSD1 in 206 EEA specimens, 50 benign endometrial lesion specimens, and 45 normal endometrium specimens. χ Analysis, Kaplan-Meier method, and multivariate Cox proportional hazard analysis were applied for the statistical analysis.

RESULTS

Compared with normal endometrium and benign endometrial lesion (both P < 0.001), LSD1 was overexpressed in EEA. LSD1 expression was correlated with histological grade, International Federation of Gynecology and Obstetrics (FIGO) stage, vascular/lymphatic invasion, depth of myometrial invasion, and lymph node metastasis. Results of the Kaplan-Meier analysis indicated that LSD1 expression was associated with overall survival (OS) and disease-free survival (DFS) of EEA. The negative expression LSD1 group had longer OS and DFS than did the positive expression group. The difference was significant (both P < 0.001, log-rank test). Multivariate Cox regression analysis revealed that the LSD1 expression status was an independent prognostic factor for both OS (P = 0.027) and DFS (P = 0.016) of patients with EEA.

CONCLUSIONS

Overexpression of LSD1 may contribute to the progression of EEA and may thus serve as a new biomarker to predict the prognosis of EEA.

LSD1: biologic roles and therapeutic targeting

LSD1 (KDM1A; BHC110; AOF2) was the first protein reported to exhibit histone demethylase activity and has since been shown to have multiple essential roles in mammalian biology. Given its enzymatic activity and its high-level expression in many human malignancies, a significant recent focus has been the development of pharmacologic inhibitors. Here we summarize structural and biochemical knowledge of this important epigenetic regulator, with a particular emphasis on the functional and preclinical studies in oncology that have provided justification for the evaluation of tranylcypromine derivative LSD1 inhibitors in early phase clinical trials.

Forced chromatin looping raises fetal hemoglobin in adult sickle cells to higher levels than pharmacologic inducers

Overcoming the silencing of the fetal γ-globin gene has been a long-standing goal in the treatment of sickle cell disease (SCD). The major transcriptional enhancer of the β-globin locus, called the locus control region (LCR), dynamically interacts with the developmental stage-appropriate β-type globin genes via chromatin looping, a process requiring the protein Ldb1. In adult erythroid cells, the LCR can be redirected from the adult β- to the fetal γ-globin promoter by tethering Ldb1 to the human γ-globin promoter with custom-designed zinc finger (ZF) proteins (ZF-Ldb1), leading to reactivation of γ-globin gene expression. To compare this approach to pharmacologic reactivation of fetal hemoglobin (HbF), hematopoietic cells from patients with SCD were treated with a lentivirus expressing the ZF-Ldb1 or with chemical HbF inducers. The HbF increase in cells treated with ZF-Ldb1 was more than double that observed with decitabine and pomalidomide; butyrate had an intermediate effect whereas tranylcypromine and hydroxyurea showed relatively low HbF reactivation. ZF-Ldb1 showed comparatively little toxicity, and reduced sickle hemoglobin (HbS) synthesis as well as sickling of SCD erythroid cells under hypoxic conditions. The efficacy and low cytotoxicity of lentiviral-mediated ZF-Ldb1 gene transfer compared with the drug regimens support its therapeutic potential for the treatment of SCD.

Fetal haemoglobin in sickle-cell disease: from genetic epidemiology to new therapeutic strategies

Sickle-cell disease affects millions of individuals worldwide, but the global incidence is concentrated in Africa. The burden of sickle-cell disease is expected to continue to rise over the coming decades, adding to stress on the health infrastructures of many countries. Although the molecular cause of sickle-cell disease has been known for more than half a century, treatment options remain greatly limited. Allogeneic haemopoietic stem-cell transplantation is the only existing cure but is limited to specialised clinical centres and remains inaccessible for most patients. Induction of fetal haemoglobin production is a promising strategy for the treatment of sickle-cell disease. In this Series paper, we review scientific breakthroughs in epidemiology, genetics, and molecular biology that have brought reactivation of fetal haemoglobin to the forefront of sickle-cell disease research. Improved knowledge of the regulation of fetal haemoglobin production in human beings and the development of genome editing technology now support the design of innovative therapies for sickle-cell disease that are based on fetal haemoglobin.

Chemical Inhibition of Histone Deacetylases 1 and 2 Induces Fetal Hemoglobin through Activation of GATA2

Therapeutic intervention aimed at reactivation of fetal hemoglobin protein (HbF) is a promising approach for ameliorating sickle cell disease (SCD) and β-thalassemia. Previous studies showed genetic knockdown of histone deacetylase (HDAC) 1 or 2 is sufficient to induce HbF. Here we show that ACY-957, a selective chemical inhibitor of HDAC1 and 2 (HDAC1/2), elicits a dose and time dependent induction of γ-globin mRNA (HBG) and HbF in cultured primary cells derived from healthy individuals and sickle cell patients. Gene expression profiling of erythroid progenitors treated with ACY-957 identified global changes in gene expression that were significantly enriched in genes previously shown to be affected by HDAC1 or 2 knockdown. These genes included GATA2, which was induced greater than 3-fold. Lentiviral overexpression of GATA2 in primary erythroid progenitors increased HBG, and reduced adult β-globin mRNA (HBB). Furthermore, knockdown of GATA2 attenuated HBG induction by ACY-957. Chromatin immunoprecipitation and sequencing (ChIP-Seq) of primary erythroid progenitors demonstrated that HDAC1 and 2 occupancy was highly correlated throughout the GATA2 locus and that HDAC1/2 inhibition led to elevated histone acetylation at well-known GATA2 autoregulatory regions. The GATA2 protein itself also showed increased binding at these regions in response to ACY-957 treatment. These data show that chemical inhibition of HDAC1/2 induces HBG and suggest that this effect is mediated, at least in part, by histone acetylation-induced activation of the GATA2 gene.

The LSD1 inhibitor RN-1 recapitulates the fetal pattern of hemoglobin synthesis in baboons (P. anubis)

Increased fetal hemoglobin levels lessen the severity of symptoms and increase the lifespan of patients with sickle cell disease. Hydroxyurea, the only drug currently approved for the treatment of sickle cell disease, is not effective in a large proportion of patients and therefore new pharmacological agents that increase fetal hemoglobin levels have long been sought. Recent studies identifying LSD-1 as a repressor of γ-globin expression led to experiments demonstrating that the LSD-1 inhibitor RN-1 increased γ-globin expression in the sickle cell mouse model. Because the arrangement and developmental stage-specific expression pattern of the β-like globin genes is highly conserved between man and baboon, the baboon model remains the best predictor of activity of fetal hemoglobin-inducing agents in man. In this report, we demonstrate that RN-1 increases γ-globin synthesis, fetal hemoglobin, and F cells to high levels in both anemic and non-anemic baboons with activity comparable to decitabine, the most potent fetal hemoglobin-inducing agent known. RN-1 not only restores high levels of fetal hemoglobin but causes the individual 5' Iγ- and 3' Vγ-globin chains to be synthesized in the ratio characteristic of fetal development. Increased fetal hemoglobin was associated with increased levels of acetylated Histone H3, H3K4Me2, H3K4Me3, and RNA polymerase II at the γ-globin gene, and diminished γ-globin promoter DNA methylation. RN-1 is likely to induce clinically relevant levels of fetal hemoglobin in patients with sickle cell disease, although careful titration of the dose may be required to minimize myelotoxicity.

Hydroxymethylcytosine and demethylation of the γ-globin gene promoter during erythroid differentiation

The mechanism responsible for developmental stage-specific regulation of γ-globin gene expression involves DNA methylation. Previous results have shown that the γ-globin promoter is nearly fully demethylated during fetal liver erythroid differentiation and partially demethylated during adult bone marrow erythroid differentiation. The hypothesis that 5-hydroxymethylcytosine (5hmC), a known intermediate in DNA demethylation pathways, is involved in demethylation of the γ-globin gene promoter during erythroid differentiation was investigated by analyzing levels of 5-methylcytosine (5mC) and 5hmC at a CCGG site within the 5′ γ-globin gene promoter region in FACS-purified cells from baboon bone marrow and fetal liver enriched for different stages of erythroid differentiation. Our results show that 5mC and 5hmC levels at the γ-globin promoter are dynamically modulated during erythroid differentiation with peak levels of 5hmC preceding and/or coinciding with demethylation. The Tet2 and Tet3 dioxygenases that catalyze formation of 5hmC are expressed during early stages of erythroid differentiation and Tet3 expression increases as differentiation proceeds. In baboon CD34+ bone marrow-derived erythroid progenitor cell cultures, γ-globin expression was positively correlated with 5hmC and negatively correlated with 5mC at the γ-globin promoter. Supplementation of culture media with Vitamin C, a cofactor of the Tet dioxygenases, reduced γ-globin promoter DNA methylation and increased γ-globin expression when added alone and in an additive manner in combination with either DNA methyltransferase or LSD1 inhibitors. These results strongly support the hypothesis that the Tet-mediated 5hmC pathway is involved in developmental stage-specific regulation of γ-globin expression by mediating demethylation of the γ-globin promoter.

Cell signaling pathways involved in drug-mediated fetal hemoglobin induction: Strategies to treat sickle cell disease

The developmental regulation of globin gene expression has shaped research efforts to establish therapeutic modalities for individuals affected with sickle cell disease and β-thalassemia. Fetal hemoglobin has been shown to block sickle hemoglobin S polymerization to improve symptoms of sickle cell disease; moreover, fetal hemoglobin functions to replace inadequate hemoglobin A synthesis in β-thalassemia thus serving as an effective therapeutic target. In the perinatal period, fetal hemoglobin is synthesized at high levels followed by a decline to adult levels by one year of age. It is known that naturally occurring mutations in the γ-globin gene promoters and distant cis-acting transcription factors produce persistent fetal hemoglobin synthesis after birth to ameliorate clinical symptoms. Major repressor proteins that silence γ-globin during development have been targeted for gene therapy in β-hemoglobinopathies patients. In parallel effort, several classes of pharmacological agents that induce fetal hemoglobin expression through molecular and cell signaling mechanisms have been identified. Herein, we reviewed the progress made in the discovery of signaling molecules targeted by pharmacologic agents that enhance γ-globin expression and have the potential for future drug development to treat the β-hemoglobinopathies.

LSD1/KDM1A promotes hematopoietic commitment of hemangioblasts through downregulation of Etv2

The hemangioblast is a progenitor cell with the capacity to give rise to both hematopoietic and endothelial progenitors. Currently, the regulatory mechanisms underlying hemangioblast formation are being elucidated, whereas those controllers for the selection of hematopoietic or endothelial fates still remain a mystery. To answer these questions, we screened for zebrafish mutants that have defects in the hemangioblast expression of Gata1, which is never expressed in endothelial progenitors. One of the isolated mutants, it627, showed not only down-regulation of hematopoietic genes but also up-regulation of endothelial genes. We identified the gene responsible for the it627 mutant as the zebrafish homolog of Lys-specific demethylase 1 (LSD1/KDM1A). Surprisingly, the hematopoietic defects in lsd1(it627) embryos were rescued by the gene knockdown of the Ets variant 2 gene (etv2), an essential regulator for vasculogenesis. Our results suggest that the LSD1-dependent shutdown of Etv2 gene expression may be a significant event required for hemangioblasts to initiate hematopoietic differentiation.

Therapeutic fetal-globin inducers reduce transcriptional repression in hemoglobinopathy erythroid progenitors through distinct mechanisms

Pharmacologic augmentation of γ-globin expression sufficient to reduce anemia and clinical severity in patients with diverse hemoglobinopathies has been challenging. In studies here, representative molecules from four chemical classes, representing several distinct primary mechanisms of action, were investigated for effects on γ-globin transcriptional repressors, including components of the NuRD complex (LSD1 and HDACs 2-3), and the downstream repressor BCL11A, in erythroid progenitors from hemoglobinopathy patients. Two HDAC inhibitors (MS-275 and SB939), a short-chain fatty acid derivative (sodium dimethylbutyrate [SDMB]), and an agent identified in high-throughput screening, Benserazide, were studied. These therapeutics induced γ-globin mRNA in progenitors above same subject controls up to 20-fold, and increased F-reticulocytes up to 20%. Cellular protein levels of BCL11A, LSD-1, and KLF1 were suppressed by the compounds. Chromatin immunoprecipitation assays demonstrated a 3.6-fold reduction in LSD1 and HDAC3 occupancy in the γ-globin gene promoter with Benserazide exposure, 3-fold reduction in LSD-1 and HDAC2 occupancy in the γ-globin gene promoter with SDMB exposure, while markers of gene activation (histone H3K9 acetylation and H3K4 demethylation), were enriched 5.7-fold. These findings identify clinical-stage oral therapeutics which inhibit or displace major co-repressors of γ-globin gene transcription and may suggest a rationale for combination therapy to produce enhanced efficacy.

Amelioration of inflammation and tissue damage in sickle cell model mice by Nrf2 activation

Sickle cell disease (SCD) is an inherited disorder caused by a point mutation in the β-globin gene, leading to the production of abnormally shaped red blood cells. Sickle cells are prone to hemolysis and thereby release free heme into plasma, causing oxidative stress and inflammation that in turn result in damage to multiple organs. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a master regulator of the antioxidant cell-defense system. Here we show that constitutive Nrf2 activation by ablation of its negative regulator Keap1 (kelch-like ECH-associated protein 1) significantly improves symptoms in SCD model mice. SCD mice exhibit severe liver damage and lung inflammation associated with high expression levels of proinflammatory cytokines and adhesion molecules compared with normal mice. Importantly, these symptoms subsided after Nrf2 activation. Although hemolysis and stress erythropoiesis did not change substantially in the Nrf2-activated SCD mice, Nrf2 promoted the elimination of plasma heme released by sickle cells' hemolysis and thereby reduced oxidative stress and inflammation, demonstrating that Nrf2 activation reduces organ damage and segregates inflammation from prevention of hemolysis in SCD mice. Furthermore, administration of the Nrf2 inducer CDDO-Im (2-cyano-3, 12 dioxooleana-1, 9 diene-28-imidazolide) also relieved inflammation and organ failure in SCD mice. These results support the contention that Nrf2 induction may be an important means to protect organs from the pathophysiology of sickle cell-induced damage.