The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases.

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) in vitro. Mode of action investigations revealed that one compound, deferasirox, is a bona fide active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.

2-Oxoglutarate regulates binding of hydroxylated hypoxia-inducible factor to prolyl hydroxylase domain 2.

Prolyl hydroxylation of hypoxia inducible factor (HIF)-α, as catalysed by the Fe(ii)/2-oxoglutarate (2OG)-dependent prolyl hydroxylase domain (PHD) enzymes, has a hypoxia sensing role in animals. We report that binding of prolyl-hydroxylated HIF-α to PHD2 is ∼50 fold hindered by prior 2OG binding; thus, when 2OG is limiting, HIF-α degradation might be inhibited by PHD binding.

Lysine-241 Has a Role in Coupling 2OG Turnover with Substrate Oxidation During KDM4-Catalysed Histone Demethylation.

The JmjC histone lysyl demethylases (KDMs) play important roles in modulating histone methylation states and have the potential to be regulated by oxygen availability. Lys241 of the KDM4 subfamily is proposed to be important in oxygen binding by KDM4A. We report evidence that, although Lys241 is unlikely to be directly involved in oxygen binding, it has an important role in coupling 2-oxoglutarate cosubstrate oxidation with lysine demethylase activity. The results suggest that compounds promoting the uncoupling of substrate oxidation are of interest as JmjC-KDM inhibitors.

Studies on the Interaction of the Histone Demethylase KDM5B with Tricarboxylic Acid Cycle Intermediates.

Methylation of lysine-4 of histone H3 (H3K4men) is an important regulatory factor in eukaryotic transcription. Removal of the transcriptionally activating H3K4 methylation is catalyzed by histone demethylases, including the Jumonji C (JmjC) KDM5 subfamily. The JmjC KDMs are Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenases, some of which are associated with cancer. Altered levels of tricarboxylic acid (TCA) cycle intermediates and the associated metabolites D- and L-2-hydroxyglutarate (2HG) can cause changes in chromatin methylation status. We report comprehensive biochemical, structural and cellular studies on the interaction of TCA cycle intermediates with KDM5B, which is a current medicinal chemistry target for cancer. The tested TCA intermediates were poor or moderate KDM5B inhibitors, except for oxaloacetate and succinate, which were shown to compete for binding with 2OG. D- and L-2HG were moderate inhibitors at levels that might be relevant in cancer cells bearing isocitrate dehydrogenase mutations. Crystallographic analyses with succinate, fumarate, L-malate, oxaloacetate, pyruvate and D- and L-2HG support the kinetic studies showing competition with 2OG. An unexpected binding mode for oxaloacetate was observed in which it coordinates the active site metal via its C-4 carboxylate rather than the C-1 carboxylate/C-2 keto groups. Studies employing immunofluorescence antibody-based assays reveal no changes in H3K4me3 levels in cells ectopically overexpressing KDM5B in response to dosing with TCA cycle metabolite pro-drug esters, suggesting that the high levels of cellular 2OG may preclude inhibition. The combined results reveal the potential for KDM5B inhibition by TCA cycle intermediates, but suggest that in cells, such inhibition will normally be effectively competed by 2OG.

The Activity of JmjC Histone Lysine Demethylase KDM4A is Highly Sensitive to Oxygen Concentrations.

The JmjC histone lysine demethylases (KDMs) are epigenetic regulators involved in the removal of methyl groups from post-translationally modified lysyl residues within histone tails, modulating gene transcription. These enzymes require molecular oxygen for catalytic activity and, as 2-oxoglutarate (2OG)-dependent oxygenases, are related to the cellular oxygen sensing HIF hydroxylases PHD2 and FIH. Recent studies have indicated that the activity of some KDMs, including the pseudogene-encoded KDM4E, may be sensitive to changing oxygen concentrations. Here, we report detailed analysis of the effect of oxygen availability on the activity of the KDM4 subfamily member KDM4A, importantly demonstrating a high level of O2 sensitivity both with isolated protein and in cells. Kinetic analysis of the recombinant enzyme revealed a high KMapp(O2) of 173 ± 23 µM, indicating that the activity of the enzyme is able to respond sensitively to a reduction in oxygen concentration. Furthermore, immunofluorescence experiments in U2OS cells conditionally overexpressing KDM4A showed that the cellular activity of KDM4A against its primary substrate, H3K9me3, displayed a graded response to depleting oxygen concentrations in line with the data obtained using isolated protein. These results suggest that KDM4A possesses the potential to act as an oxygen sensor in the context of chromatin modifications, with possible implications for epigenetic regulation in hypoxic disease states. Importantly, this correlation between the oxygen sensitivity of the catalytic activity of KDM4A in biochemical and cellular assays demonstrates the utility of biochemical studies in understanding the factors contributing to the diverse biological functions and varied activity of the 2OG oxygenases.

Targeting Protein-Protein Interactions in the HIF System.

Animals respond to chronic hypoxia by increasing the levels of a transcription factor known as the hypoxia-inducible factor (HIF). HIF upregulates multiple genes, the products of which work to ameliorate the effects of limited oxygen at cellular and systemic levels. Hypoxia sensing by the HIF system involves hydroxylase-catalysed post-translational modifications of the HIF α-subunits, which 1) signal for degradation of HIF-α and 2) limit binding of HIF to transcriptional coactivator proteins. Because the hypoxic response is relevant to multiple disease states, therapeutic manipulation of the HIF-mediated response has considerable medicinal potential. In addition to modulation of catalysis by the HIF hydroxylases, the HIF system manifests other possibilities for therapeutic intervention involving protein-protein and protein-nucleic acid interactions. Recent advances in our understanding of the structural biology and biochemistry of the HIF system are facilitating medicinal chemistry efforts. Herein we give an overview of the HIF system, focusing on structural knowledge of protein-protein interactions and how this might be used to modulate the hypoxic response for therapeutic benefit.

Epigenetic regulation by histone demethylases in hypoxia.

The response to hypoxia is primarily mediated by the hypoxia-inducible transcription factor (HIF). Levels of HIF are regulated by the oxygen-sensing HIF hydroxylases, members of the 2-oxoglutarate (2OG) dependent oxygenase family. JmjC-domain containing histone lysine demethylases (JmjC-KDMs), also members of the 2OG oxygenase family, are key epigenetic regulators that modulate the methylation levels of histone tails. Kinetic studies of the JmjC-KDMs indicate they could also act in an oxygen-sensitive manner. This may have important implications for epigenetic regulation in hypoxia. In this review we examine evidence that the levels and activity of JmjC-KDMs are sensitive to oxygen availability, and consider how this may influence their roles in early development and hypoxic disease states including cancer and cardiovascular disease.

Hip fractures in people with idiopathic Parkinson's disease: incidence and outcomes.

The incidence of hip fracture and outcomes from hip surgery for people with Parkinson's disease (PD) are thought to be poorer than for people without PD. The aim of this audit of a prospective hip-fracture database was to establish the incidence of, and outcomes from, hip fracture in people with and without PD living in North East England. The number of people with PD living in the study area was estimated using data from two previous prevalence studies in the same geographical area. Using data collected prospectively for the National Hip Fracture Database for Northumbria Healthcare National Health Service Foundation Trust in the UK, the annual incidence of hip fracture in people with and without PD was calculated. Type of fracture, time to surgery, time to discharge, and 30-day outcomes from surgery were compared. Annual incidence of hip fracture was significantly higher in people with PD across all age bands. In those 60 years of age and over, it was 2,171 (95% confidence interval [CI]: 2,082-2,264) per 100,000 in people with PD and 551 (95% CI: 506-598) in people without PD. The experience of PD and non-PD patients within hospital was remarkably similar. However, PD patients had poorer mobility before hip fracture, took longer to be discharged to the community, and were less mobile postsurgery. Specific guidelines for managing people with PD who sustain a hip fracture may help to improve awareness of the potential complications of the condition and improve outcomes.

International practices in the provision of teratology information: a survey of international teratogen information programmes and comparisons with the North American model.

RATIONALE, AIMS AND OBJECTIVES: Teratology Information Services (TIS) provide health care professionals and the public with information regarding the safety and/or risk of exposures during pregnancy and lactation, mainly via telephone consultations. An international comparison of clinical practices at TIS has never been conducted. The survey objective was to compare international TIS to North American TIS, with an aim to identify strengths and challenges that can lead to service improvement. METHODS: Twenty-two international TIS were approached for participation during an international conference. TIS were surveyed on information in six categories: services, staffing, operations, data collection, knowledge transfer activities and additional information. Data were summarized using descriptive statistics. Statistical tests were conducted using SPSS®. RESULTS: Sixteen TIS from 12 countries participated. Survey results were compared with previously reported results from a similar survey of North American TIS (16 US, two Canadian). TIS exist in a variety of departments and settings, but most commonly are in university hospitals. Pregnant women were the most commonly counselled group worldwide. International TIS spent significantly more time fielding inquiries regarding medications, while North American TIS had a wider variety of inquiry categories. All TIS could improve budget tracking. CONCLUSIONS: Overall, service practices and goals were similar, although international TIS conducted more follow-up with service users than North American TIS. This report offers TIS the first ever opportunity to compare practices. Increased dialogue between TIS encourages sharing of best practices and improves the ability of these important public health programmes to support women and health care providers.

Providing information regarding exposures in pregnancy: a survey of North American Teratology Information Services.

PURPOSE: Teratology Information Services (TIS) provide information on exposures during pregnancy and breast-feeding. Maintaining ongoing funding is a challenge. The purpose was to gather descriptive information on current TIS operations. METHODS: All North American TIS (16 American, 2 Canadian) completed a detailed survey. RESULTS: Service goal ranked as most important was correction of risk misperceptions. Inquiries were primarily for medications (mean 43.5%, S.D. 14.1), lactation exposures, and workplace exposures. Median employees per TIS: three (range 1-12.5). Two TIS only counsel health care professionals (HCPs). Main callers to remaining TIS were pregnant women (mean 46.8%, S.D. 22.8), physicians, and nurses. Calls per week varied (median 20, range 4-600). Median annual budget: US dollars 69,000 (range dollars 3000-335,000). Seventeen TIS collect patient data for research. CONCLUSIONS: This survey was the first to document TIS operations in North America and demonstrates a spectrum of clinical and research activities, and provides data for a future cost-benefit analysis of TIS.

The effectiveness of Teratology Information Services (TIS).

BACKGROUND: Women and their health care providers have few reliable sources of information regarding the safety of exposures in pregnancy and lactation. Evidence-based information on these topics is provided by Teratology Information Services (TIS). Access to TIS, however, is limited in many regions, and many services have difficulty maintaining ongoing funding. The objective of this review is to highlight published reports of the effectiveness of TIS in improving maternal and neonatal health. METHODS: A search of the Pub Med and Econ Lit databases was performed with no date restriction, using the search terms teratology, information, counseling, pregnancy, effectiveness, birth defects. RESULTS: Information disseminated from TIS has been shown to prevent congenital malformations, unnecessary pregnancy terminations, and occupational risks. TIS support optimal nutritional supplementation in pregnancy and optimal drug therapy in pregnancy and breast-feeding. In addition, they correct misperceptions of risk and facilitate knowledge transfer and translation. TIS have the potential to provide health care cost savings. CONCLUSIONS: TIS are vital services in supporting optimal maternal and neonatal health. A formal economic evaluation of TIS is required in order to inform resource allocation decision-making and continued funding of these services.