Friedreich's Ataxia & Iron
Accumulation
This article submitted by on 11/8/97.
FRIEDREICH'S ATAXIA: FRATAXIN AND IRON ACCUMULATION IN THE
MITOCHONDRIA
Fraser J. Goodmurphy, London, Canada
Massimo Pandolfo, Centre de Recherche Louis-Charles Simard,
Montreal, Canada
In the 8 March 1996 issue of SCIENCE, Doctor Massimo
Pandolfo and his colleagues in Houston, Texas and around the
world announced that they had cloned the gene responsible
for Friedreich's Ataxia (FRDA), a recessively inherited
neurodegenerative disorder characterized by a wide range of
symptoms including cardiac, muscular-skeletal, and metabolic
complications. Its cause has remained a mystery and has been
untreatable since it was first identified by Nicholaus
Friedreich, a Professor of Medicine in Heidelberg, Germany,
over 120 years ago. Since relocating to Montreal, Canada,
Doctor Pandolfo and a number of laboratories in Canada, the
United States, France, Italy, and Belgium have clarified how
lack of FRATAXIN - the protein expressed by the FRDA gene
X25 - appears to cause FRDA and how this cause MIGHT
eventually be treated. Although the connection between the
role of Frataxin and the cause of FRDA is based on THEORY
and OBSERVATION at the moment, it may eventually lead to a
clinical trial. NO drugs are currently available to safely
and effectively treat or cure the cause of this disorder but
this research remains a significant breakthrough. It offers
us a new and valid reason to hope that a treatment to halt
or slow the progression of FRDA might be on the horizon.
During the past year, laboratories around the world have
observed that Frataxin is apparently a mitochondrial
protein, concentrated in the tiny structures inside cells
which convert food into energy. When Doctor Jerry Kaplan and
his colleagues at the University of Utah "knocked out" a
gene in Baker's Yeast (Yeast Frataxin Homologue 1, YFH1)
which is genetically similar to X25, iron accumulates in the
mitochondria causing mitochondrial disfunction, possibly by
catalyzing the production of free radicals; by "chemically
helping" the formation of unstable molecules which destroy
nerves and organs. These observations, which appear in the
Friday 13 June 1997 issue of SCIENCE in an article
co-authored by Doctor Pandolfo, suggest that the process of
iron accumulation in the mitochondria could be studied
within FRDA cells grown in a test tube, and if the
accumulation appears to cause the degeneration
characteristic of FRDA, the efficacy of iron chelators -
drugs which remove iron from cells - could be evaluated for
protecting these cells. If the relationship proves to be
valid and reliable, an investigation of the therapeutic
benefits of iron chelating drugs alone or in combination
with antioxidants such as Vitamin E among individuals who
have been diagnosed with FRDA may be considered.
While this news is very exciting, a number of caveats about
the hypothesis itself and the method in which it ought to be
tested need to be addressed before it can be applied,
especially among humans. Obviously, our cells are infinitely
more complicated than Yeast cells. Because we cannot live
without functional mitochondria and because our cells
contain a varying amount of them, unlike yeast, the
connection between iron accumulation and the degeneration
characteristic of FRDA may not be as straightforward as it
first appears. Furthermore, as all of us who have been
diagnosed with FRDA express some amount of residual Frataxin
no matter how much our DNA differs from the norm,
observations drawn from Yeast cells may not be entirely
compatible with the processes that cause FRDA in humans. A
number of laboratories around the world are diligently
working on developing a "transgenic" model of FRDA in mice
in order to study how Frataxin functions in organisms that
are closer to humans but none of them have published results
to date.
Although a published result indicates
that a single individual has been successfully treated for
Aceruloplasminemia, an autosomal-recessive neurodegenerative
disorder characterized by iron overload in the Central
Nervous System, with an iron chelator, the particular drug
has a number of drawbacks. It is very expensive, it is not
overly effective in children, and occasionally it has some
toxic side effects. Furthermore, it is not administered
orally, but injected or infused by a small pump. An oral
medication is currently in Clinical Trials in Canada and
Europe but evidence of its safety and effectiveness in
chelating iron - eliminating it from iron-overloaded cells -
remains inconclusive. The problem of measuring the extent of
iron overload and free radical damage among those of us with
FRDA is equally complicated. Minerals cannot be easily
visualized by non-invasive investigative techniques such as
Magnetic Resonance Imaging (MRI), which actually images
structures according to their difference in water content.
Similarly, free radical production and damage are impossible
to quantify in living organisms at the moment. Procedures
may be developed, however, to increase the sensitivity of
MRI to iron, and experiments aimed at extending free radical
assessment beyond tissue samples and cultured cells to those
of us with FRDA are currently underway.
These latter concerns need to be
addressed because the severity and symptoms of FRDA vary so
much. Before anyone who has been diagnosed with FRDA can be
treated with an iron chelator or an antioxidant, we need to
confirm beyond a reasonable doubt that iron accumulation in
the mitochondria is indeed the primary cause of the
progression of FRDA, and that this kind of treatment is safe
and effective. A number of circumstances however, warrant
optimism. Another Neurologist at the University of
Sherbrooke in Quebec observed iron accumulation in the
mitochondria of the heart cells among those of us with FRDA
almost 20 years ago. Up to this year, the cause of the
accumulation remained a mystery - until genetic science
advanced far enough to reveal that the protein expressed by
X25 appears to cause the iron accumulation which seems to
produce FRDA. At the recent First International Symposium on
Inherited Ataxias held in Montreal, Doctor Pandolfo took the
names of over 20 Neurologists and Geneticists from Canada,
the United States, England, Italy, Spain, France, Germany,
Australia, and Russia who are interested in investigating
the possibilities of treating this accumulation with iron
chelators and antioxidants.
This global committee needs to meet a
number of critical aims before rushing into Clinical Trials:
development of a working model of FRDA in mice, development
of a safe and effective iron chelator, selection of an
appropriate antioxidant, and development of meaningful
measurements of effects. According to Doctor Pandolfo, the
committee wants to "do this right". They urge you to refrain
from asking your Doctor for any sort of iron chelator, and
they advise you not to attempt to completely eliminate iron
from your diet because iron deprivation directly causes a
number of other disorders which are just as serious as FRDA.
We have all been waiting a long time for this news.
Encouraging results may be published sooner than you might
expect. In the meantime, because FRDA research is not well
supported, you may want to consider helping fund this
project by donating your time or money to one of the
organizations which fund Ataxia research in your country.
Speaking as someone who has been coping with FRDA for 20
years, I believe that we all have a valid reason to be
optimistic about the possibility of a viable treatment
becoming available in the near future.
--
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