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2) - FRDA treatment
We therefore predicted as early as 1999 that the use of a mitochondrially-targeted antioxidant should lessen the consequences of frataxin depletion. We thus rapidly initiated the first clinical trial using idebenone, with some success at least on the heart hypertrophy frequently noticed in patients . Then, we suggested to use an alternative approach directly targeting the loss of frataxin function, the initial step of the disease. With this aim, we suggested attempting to increase the overall transcription of mitochondrial proteins and mitochondrial antioxidant components, including frataxin itself, by testing a PPAR gamma ligand. Thus we selected Pioglitazone a drug previously recommended to fight diabetes, but which was also shown to have protective effect in other neurological diseases. Following this suggestion, a double-blind placebo-controlled trial started in October 2008 in our hospital (2 years; 40 patients).
Our project: Identifying additional sensitive targets in Friedreich ataxia
By trialling the use of Pioglitazone and Idebenone, we targeted the initial and terminal steps of Friedreich ataxia. We now have the idea to target additional, intermediate and critical step(s) in the cellular consequences of frataxin depletion.
So far, it is quite difficult to order the different aspects of the cellular consequences of frataxin depletion, i.e. the loss of iron-sulfur clusters, the oxidative stress and the mitochondrial iron accumulation. Dealing with this latter, there is however a number of evidences, both in human and mouse defective in frataxin, suggesting that iron accumulation is rather a late phenomenon. Additionally, we recently provided evidence that chelating mitochondrial iron is a dangerous double-edged sword. Indeed severe mitochondrial iron depletion will result in the blockade of iron-requiring biosynthesis pathways (iron-sulfur and heme synthesis), ultimately resulting in cell death . As a consequence, any long-term use of chelators targeting mitochondrial iron might thus reveal quite dangerous in human.
Interestingly enough, the loss of iron-sulfur cluster has been shown to be oxygen-dependent in frataxin-depleted yeast mutants, and human fibroblasts with low frataxin displayed increased-sensitivity to oxidative insult, yet with normal activity of the iron-sulfur cluster containing enzymes. This suggested that hyper sensitivity to oxidative stress is a very early event, possibly preceding iron-sulfur cluster quantitative loss. We and other ascribed this hyper sensitivity to impaired superoxide dismutase induction upon oxidative insult [4; 7]. More recently we established that this originated from a more general impairment of phase II antioxidant enzymes by the transcription factor Nrf2 .
While several groups devote a lot of effort to decipher the function of frataxin in the biosynthesis of iron-sulphur clusters, we rather decided in this new project to focus our attention on the mechanism which might explain the loss of Nrf2 function associated with the frataxin depletion. This unknown mechanism might shade new light on the frataxin function, help to identify new targets and open the way to a novel way to counteract the disease.
This is a several years project which will involve a number of steps:
A) Deciphering the nature and composition of the protein complex binding the actin-anchored Nrf2 to the mitochondria. Attempt to perform this analysis will be done by studying various human cell lines (including cells derived from neural tissues such as SK-N-AS) and primary human cells (skin fibroblasts). To note, we already know some of the components of this complex which will help for the identification of its other members.
- 1. Study will include BN page analysis of the predicted complex under non-denaturating conditions, using the available series of antibodies targeting putative members of the complex. The complex will be obtained by standard pull-down methods starting by cellular disruption using mild conditions.
- 2. If required, mass spectrometry-based analysis of the putative complex either using tandem affinity purification of tagged proteins of interest (possibly increasing the signal-to-noise ratio via the generation of clean samples), or by stable isotopic labelling of proteins to possibly discriminate between contaminants and bona fide binding partners using quantitative MS techniques. The recent recruitment in our group of a specialist of these techniques will make them readily available for the project if needed, the machine being by the way available in our hospital.
- 3. Exclusion of the participation of a sub-pool of Frataxin might be at the end of this part, since such a putative sub-pool has been suggested to exist in cell cytosol.
- 4. Parallel study with a similar series of analyses will, in a second step, be performed on patient cell lines. We already established that the phenotype of these cells already indicates a loss of Nrf2 anchoring to the actin network .
B) Targeting the various members of the complex. In this part of the project we will assess/check the relative role of the various components of the complex, in particular their role in the sensitivity to oxidative stress
- 1. we will make use of shRNA to extinct the various targets (the components of the complex) in a cell line (Flp-In T-Rex HEK-293) which allows a unique and directed insertion at a defined locus which expression can be in addition modulated by doxycycline. We previously used this approach successfully to over express an allotopic protein in the respiratory chain . Extinction of the targeted gene expression will be checked by quantitative PCR and/or Western blotting.
- 2. the obtained cells will be extensively characterized for their phenotype, especially for potential hampering of their sensitivity to oxidative stress. This will give us the opportunity to modulate cell culture conditions to determine if we can not modulate the consequences, possibly including iron-sulfur clusters stability, in these various cells.
C) The missing link… In this part of the project, we will attempt to characterize the link existing between the mitochondrial-matrix located frataxin and the cytosolic-located Nrf2-containing complex. Several hypotheses can be drawn to explain the disorganisation of the complex associated with frataxin-depletion.
- 1. The first hypothesis is the over-production of oxidant species from frataxin-depleted mitochondria in patient fibroblasts. We will test this hypothesis by using redox-sensitive fluorescent probes, knowing that the flux of electrons in the respiratory chain of these frataxin-depleted cultured cells is not quantitatively affected. A whole set of respiratory chain deficient cells already known as producing such oxidant species will be used as positive controls.
- 2. The second hypothesis would require the existence of an iron-sulfur protein in the Nrf2-binding complex which would be exquisitely sensitive (as compared to other ISP) to a decrease of the mitochondrial frataxin content. Indication about the occurrence of such protein could arise from the first part of this study. A protein as GRX2 which binds iron-sulfur cluster to dimerize would have been a perfect candidate, but we previously established that it is not affected in frataxin-depleted fibroblasts .
D) Restoring the normal response to oxidative insult. We previously established that trapping hydrogen peroxides (one of the oxidant compound released by mitochondria), restore Nrf2 normal function in patient fibroblasts. However, trapping hydrogen peroxide can have a whole series of consequences not necessarily restricted to or mediated by an effect on the Nrf2-binding complex, we would like to:
- 1. Analyse/demonstrate the consequence of trapping the peroxide on the stability of the complex.
-2. Identify new compounds able to relocated Nrf2 in frataxin-depleted cells. For these part of the study we will used patient derived fibroblasts (immortalized fast growing cell line), using oxidant-induced cell death (tracing restored Nrf2 localization) as a criterion, and use the bank of compounds (80 000) we previously tested in previous research programs we were involved in.
Final deliverables might (should!) include:
- a better understanding of the hampered response of frataxin-depleted cell to oxidative stress;
- characterization of a protein complex (and associated signaling pathway) which might well play a considerable role in Friedreich ataxia and other neurodegenerative conditions as well;
- identification of new target(s) and new compound(s) to be trialled to counteract Friedreich ataxia
1. Campuzano V, Montermini L, Molto MD, Pianese L, Cossee M, Cavalcanti F, Monros E, Rodius F, Duclos F, Monticelli A, Zara F, Canizares J, Koutnikova H, Bidichandani SI, Gellera C, Brice A, Trouillas P, De Michele G, Filla A, De Frutos R, Palau F, Patel PI, Di Donato S, Mandel JL, Cocozza S, Koenig M, Pandolfo M. Friedreich's ataxia: autosomal recessive disease caused by an intronic GAA triplet repeat expansion. Science 1996; 271; 1423-1427
2. Rotig A, de Lonlay P, Chretien D, Foury F, Koenig M, Sidi D, Munnich A, Rustin P. Aconitase and mitochondrial iron-sulphur protein deficiency in Friedreich ataxia. Nat Genet 1997; 17; 215-217
3. von Kleist-Retzow JC, Chantrel-Groussard K, Rotig A, Munnich A, Rustin P. [Friedreich ataxia. 3 years after the identification of the gene a glimmer of hope for therapy]. Dtsch Med Wochenschr 2000; 125; 293-295
4. Chantrel-Groussard K, Geromel V, Puccio H, Koenig M, Munnich A, Rotig A, Rustin P. Disabled early recruitment of antioxidant defenses in Friedreich's ataxia. Hum Mol Genet 2001; 10; 2061-2067
5. Rustin P, von Kleist-Retzow JC, Chantrel-Groussard K, Sidi D, Munnich A, Rotig A. Effect of idebenone on cardiomyopathy in Friedreich's ataxia: a preliminary study. Lancet 1999; 354; 477-479
6. Goncalves S, Paupe V, Dassa EP, Rustin P. Deferiprone targets aconitase: implication for Friedreich's ataxia treatment. BMC Neurol 2008; 8; 20
7. Jiralerspong S, Ge B, Hudson TJ, Pandolfo M. Manganese superoxide dismutase induction by iron is impaired in Friedreich ataxia cells. FEBS Lett 2001; 509; 101-105
8. Paupe V, Dassa EP, Goncalves S, Auchere F, Lonn M, Holmgren A, Rustin P. Impaired nuclear Nrf2 translocation undermines the oxidative stress response in Friedreich ataxia. PLoS ONE 2009; 4; e4253
9. Dassa EP, Dufour E, Goncalves S, Paupe V, Hakkaart G, Jacobs HT, Rustin P. Expressing the alternative oxidase complements cytochrome c oxidase deficiency in human cells. EMBO Mol Med 2009; 1; 30-36
10. Dassa EP, Paupe V, Goncalves S, Rustin P. The mtDNA NARP mutation activates the actin-Nrf2 signaling of antioxidant defenses. Biochem Biophys Res Commun 2008; 368; 620-624
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The life of Marie Schlau, a German Jewish girl born in 1833 hides great unsolved mysteries: accidents, disappearances, enigmas, unknown diagnoses, disturbing murders, love, tenderness, greed, lies, death ... alternatively a different story unfolds every time and takes us closer to the present. Thus, there are two parallel stories unravelling, each in a different age and place, which surprisingly converge in a revelatory chapter.
Paperback and Kindle versions for "The legacy of Marie Schlau" available for sale at Amazon now!
Currently, BabelFAmily is financing two promising research projects aimed at finding a cure for Friedreich's Ataxia. Whenever you make a donation to us or purchase a copy of "The legacy of Marie Schlau", this is where all funds raised will be devoted to:
1) Gene Therapy for Friedreich's Ataxia research project:
The project is the result of an initiative of Spanish people affected by this rare disease who are grouped in GENEFA in collaboration with the Spanish Federation of Ataxias and the BabelFAmily. The Friedreich’s Ataxia Research Alliance (FARA), one of the main patients’ associations in the United States now joins the endeavour.
2) Frataxin delivery research project:
The associations of patients and families Babel Family and the Asociación Granadina de la Ataxia de Friedreich (ASOGAF) channel 80,000 euros of their donations (50% from each organisation) into a new 18-month project at the Institute for Research in Biomedicine (IRB Barcelona). The project specifically aims to complete a step necessary in order to move towards a future frataxin replacement therapy for the brain, where the reduction of this protein causes the most damage in patients with Friedreich’s Ataxia.
The study is headed by Ernest Giralt, head of the Peptides and Proteins Lab, who has many years of experience and is a recognised expert in peptide chemistry and new systems of through which to delivery drugs to the brain, such as peptide shuttles—molecules that have the capacity to carry the drug across the barrier that surrounds and protects the brain. Since the lab started its relation with these patients’ associations in 2013*, it has been developing another two projects into Friedrich’s Ataxia.