Why should neuroscientists worry about iron? The emerging role of ferroptosis in the pathophysiology of neuroprogressive diseases

Gerwyn Morris, Michael Berk, André F. Carvalho, Michael Maes, Adam J. Walker, Basant K. Puri, Behavioural Brain Research, Available online 28 December 2017, ISSN 0166-4328, doi:10.1016/j.bbr.2017.12.036.

Ferroptosis is a unique form of programmed death, characterised by cytosolic accumulation of iron, lipid hydroperoxides and their metabolites, and effected by the fatal peroxidation of polyunsaturated fatty acids in the plasma membrane. It is a major driver of cell death in neurodegenerative neurological diseases. Moreover, cascades underpinning ferroptosis could be active drivers of neuropathology in major psychiatric disorders. Oxidative and nitrosative stress can adversely affect mechanisms and proteins governing cellular iron homeostasis, such as the iron regulatory protein/iron response element system, and can ultimately be a source of abnormally high levels of iron and a source of lethal levels of lipid membrane peroxidation. Furthermore, neuroinflammation leads to the upregulation of divalent metal transporter-1 on the surface of astrocytes, microglia and neurones, making them highly sensitive to iron overload in the presence of high levels of non-transferrin-bound iron, thereby affording such levels a dominant role in respect of the induction of iron-mediated neuropathology. Mechanisms governing systemic and cellular iron homeostasis, and the related roles of ferritin and mitochondria are detailed, as are mechanisms explaining the negative regulation of ferroptosis by glutathione, glutathione peroxidase 4, the cysteine/glutamate antiporter system, heat shock protein 27 and nuclear factor erythroid 2-related factor 2. The potential role of DJ-1 inactivation in the precipitation of ferroptosis and the assessment of lipid peroxidation are described. Finally, a rational approach to therapy is considered, with a discussion on the roles of coenzyme Q10, iron chelation therapy, in the form of deferiprone, deferoxamine (desferrioxamine) and deferasirox, and N-acetylcysteine.

Association between iron related gene polymorphisms and Friedreich’s ataxia (FRDA) disease and peripheral neuropathy in Indian cohort

I. Singh, S. Shakya, R.K. Singh, A. Istaq, V. Goyal, S. Garima, A.K. Srivastava; Journal of the Neurological Sciences Volume 381, Supplement, 15 October 2017, Pages 895 Doi: 10.1016/j.jns.2017.08.2519

Till date, this is the largest study investigating HFE variations in FRDA. The observed over representation of p.H63D variation in FRDA and its correlation with the occurrence of peripheral neuropathy is intriguing in the context of dysregulated iron metabolism in FRDA due to loss of function mutations in FXN.

Transcriptional regulators of redox balance and other homeostatic processes with the potential to alter neurodegenerative disease trajectory.

Scott W. Burnside, Giles E. Hardingham; Biochemical Society Transactions Nov 17, 2017, 45 (6) 1295-1303; DOI: 10.1042/BST20170013

Diverse neurodegenerative diseases share some common aspects to their pathology, with many showing evidence of disruption to the brain's numerous homeostatic processes. As such, imbalanced inflammatory status, glutamate dyshomeostasis, hypometabolism and oxidative stress are implicated in many disorders. That these pathological processes can influence each other both up- and downstream makes for a complicated picture, but means that successfully targeting one area may have an effect on others. This targeting requires an understanding of the mechanisms by which homeostasis is maintained during health, in order to uncover strategies to boost homeostasis in disease. A case in point is redox homeostasis, maintained by antioxidant defences co-ordinately regulated by the transcription factor Nrf2, and capable of preventing not only oxidative stress but also inflammation and neuronal loss in neurodegenerative disease models. The emergence of other master regulators of homeostatic processes in the brain controlling inflammation, mitochondrial biogenesis, glutamate uptake and energy metabolism raises the question as to whether they too can be targeted to alter disease trajectory.

NAD+ Intermediates: The Biology and Therapeutic Potential of NMN and NR

Jun Yoshino, Joseph A. Baur, Shin-ichiro Imai,  Cell Metabolism, Available online 14 December 2017, ISSN 1550-4131, doi:10.1016/j.cmet.2017.11.002.

Research on the biology of NAD+ has been gaining momentum, providing many critical insights into the pathogenesis of age-associated functional decline and diseases. In particular, two key NAD+ intermediates, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), have been extensively studied over the past several years. Supplementing these NAD+ intermediates has shown preventive and therapeutic effects, ameliorating age-associated pathophysiologies and disease conditions. Although the pharmacokinetics and metabolic fates of NMN and NR are still under intensive investigation, these NAD+ intermediates can exhibit distinct behavior, and their fates appear to depend on the tissue distribution and expression levels of NAD+ biosynthetic enzymes, nucleotidases, and presumptive transporters for each. A comprehensive concept that connects NAD+ metabolism to the control of aging and longevity in mammals has been proposed, and the stage is now set to test whether these exciting preclinical results can be translated to improve human health.

Friedreich and dominant ataxias: quantitative differences in cerebellar dysfunction measurements

Tanguy Melac A, Mariotti C, Filipovic Pierucci A on behalf of the EFACTS group, et al; J Neurol Neurosurg Psychiatry Published Online First: 26 December 2017. doi: 10.1136/jnnp-2017-316964

Cerebellar dysfunction, as measured with the CCFS and SARA scales, was more severe in FRDA than in patients with SCA, but with lower progression indexes, within the limits of these types of indexes. Ceiling effects may occur at late stages, for both scales. The CCFS scale is rater-independent and could be used in a multicentre context, as it is simple, rapid and fully automated.

The International Rare Diseases Research Consortium: Policies and Guidelines to maximize impact

Hanns Lochmüller, Josep Torrent i Farnell, Yann Le Cam, Anneliene H Jonker, Lilian PL Lau, Gareth Baynam, Petra Kaufmann, Hugh JS Dawkins, Paul Lasko, Christopher P Austin, Kym M Boycott & on behalf of the IRDiRC Consortium Assembly; European Journal of Human Genetics 25, 1293–1302 (2017) doi:10.1038/s41431-017-0008-z

The IRDiRC Policies and Guidelines are the first, detailed agreement of major public and private funding organizations worldwide to govern rare disease research, and may serve as a template for other areas of international research collaboration. While it is too early to assess their full impact on research productivity and patient benefit, the IRDiRC Policies and Guidelines have already contributed significantly to improving transparency and collaboration in rare disease research.

Exploring patient and family involvement in the lifecycle of an orphan drug: a scoping review

Andrea Young, Devidas Menon, Jackie Street, Walla Al-Hertani and Tania Stafinski; Orphanet Journal of Rare Diseases 201712:188 doi:10.1186/s13023-017-0738-6

Patients and their families have become more active in healthcare systems and research. The value of patient involvement is particularly relevant in the area of rare diseases, where patients face delayed diagnoses and limited access to effective therapies due to the high level of uncertainty in market approval and reimbursement decisions. It has been suggested that patient involvement may help to reduce some of these uncertainties. This review explored existing and proposed roles for patients, families, and patient organizations at each stage of the lifecycle of therapies for rare diseases (i.e., orphan drug lifecycle).

Early VGLUT1-specific parallel fiber synaptic deficits and dysregulated cerebellar circuit in the KIKO mouse model of Friedreich ataxia

Hong Lin, Jordi Magrane, Elisia M. Clark, Sarah M. Halawani, Nathan Warren, Amy Rattelle, David R. Lynch; Disease Models & Mechanisms 2017 10: 1529-1538; doi: 10.1242/dmm.030049

Here, we report early cerebellar VGLUT1 (SLC17A7)-specific parallel fiber (PF) synaptic deficits and dysregulated cerebellar circuit in the frataxin knock-in/knockout (KIKO) FRDA mouse model. At asymptomatic ages, VGLUT1 levels in cerebellar homogenates are significantly decreased, whereas VGLUT2 (SLC17A6) levels are significantly increased, in KIKO mice compared with age-matched controls. Additionally, GAD65 (GAD2) levels are significantly increased, while GAD67 (GAD1) levels remain unaltered. This suggests early VGLUT1-specific synaptic input deficits, and dysregulation of VGLUT2 and GAD65 synaptic inputs, in the cerebellum of asymptomatic KIKO mice. Immunohistochemistry and electron microscopy further show specific reductions of VGLUT1-containing PF presynaptic terminals in the cerebellar molecular layer, demonstrating PF synaptic input deficiency in asymptomatic and symptomatic KIKO mice. Moreover, the parvalbumin levels in cerebellar homogenates and Purkinje neurons are significantly reduced, but preserved in other interneurons of the cerebellar molecular layer, suggesting specific parvalbumin dysregulation in Purkinje neurons of these mice. Furthermore, a moderate loss of large principal neurons is observed in the dentate nucleus of asymptomatic KIKO mice, mimicking that of FRDA patients. Our findings thus identify early VGLUT1-specific PF synaptic input deficits and dysregulated cerebellar circuit as potential mediators of cerebellar dysfunction in KIKO mice, reflecting developmental features of FRDA in this mouse model.

Liquid Chromatography-High Resolution Mass Spectrometry Analysis of Platelet Frataxin as a Protein Biomarker for the Rare Disease Friedreich’s Ataxia

Lili Guo, Qingqing Wang, Liwei Weng, Lauren A. Hauser, Cassandra J. Strawser, Agostinho G. Rocha, Andrew Dancis, Clementina A Mesaros, David R. Lynch, and Ian Alexander Blair; Anal. Chem., Just Accepted Manuscript DOI: 10.1021/acs.analchem.7b04590 Publication Date (Web): December 22, 2017

Frataxin is undetectable in serum or plasma, and whole blood cannot be used because it is present in long-lived erythrocytes. Therefore, an assay was developed for analyzing frataxin in platelets, which have a half-life of 10-days. The assay is based on stable isotope dilution immunopurification two-dimensional nano-ultrahigh performance liquid chromatography/parallel reaction monitoring/mass spectrometry. The lower limit of quantification was 0.078 pg frataxin/μg protein and the assay had 100% sensitivity and specificity for discriminating between controls and FA cases. The mean levels of control and FA platelet frataxin were 9.4 2.6 pg/g protein and 2.4 0.6 pg/g protein, respectively. The assay should make it possible to rigorously monitor the effects of therapeutic interventions on frataxin expression in this devastating disease.

Somatic instability of the expanded GAA repeats in Friedreich’s ataxia

Ashlee Long, Jill S. Napierala, Urszula Polak, Lauren Hauser, Arnulf H. Koeppen, David R. Lynch, Marek Napierala; PLoS ONE 12(12): e0189990. Doi:10.1371/journal.pone.0189990

Friedreich’s ataxia (FRDA) is a genetic neurodegenerative disorder caused by transcriptional silencing of the frataxin gene (FXN) due to expansions of GAA repeats in intron 1. FRDA manifests with multiple symptoms, which may include ataxia, cardiomyopathy and diabetes mellitus. Expanded GAA tracts are genetically unstable, exhibiting both expansions and contractions. GAA length correlates with severity of FRDA symptoms and inversely with age of onset. Thus, tissue-specific somatic instability of long GAA repeats may be implicated in the development of symptoms and disease progression. Herein, we determined the extent of somatic instability of the GAA repeats in heart, cerebral cortex, spinal cord, cerebellar cortex, and pancreatic tissues from 15 FRDA patients. Results demonstrate differences in the lengths of the expanded GAAs among different tissues, with significantly longer GAA tracts detected in heart and pancreas than in other tissues. The expansion bias detected in heart and pancreas may contribute to disease onset and progression, making the mechanism of somatic instability an important target for therapy. Additionally, we detected significant differences in GAA tract lengths between lymphocytes and fibroblast pairs derived from 16 FRDA patients, with longer GAA tracts present in the lymphocytes. This result urges caution in direct comparisons of data obtained in these frequently used FRDA models. Furthermore, we conducted a longitudinal analysis of the GAA repeat length in lymphocytes collected over a span of 7–9 years and demonstrated progressive expansions of the GAAs with maximum gain of approximately 9 repeats per year. Continuous GAA expansions throughout the patient’s lifespan, as observed in FRDA lymphocytes, should be considered in clinical trial designs and data interpretation.