Subject: IRON DEPRIVATION

ABSTRACT
The recent finding of the beneficial effects of iron deprivation in the
outcome of muscle necrosis in an animal model of genetic myopathy served
as the basis of this commentary. Here, "taking away" iron by controlled
dietary deprivation is proposed as a reasonable, feasible, cheap, and
efficient clinical approach to many diverse diseases, all of which have a
free radical component. Indeed, iron potentiates the generation of the
highly reactive and toxic hydroxyl radical, and , thus , of oxidative
damage. Iron deprivation may represent the first really efficient
antioxidant, preventing oxidative stress in all subcellular compartments,
tissues, and organs. Iron/iron deprivation also modulates programmed cell
death (apoptosis) , which should be the subject of further studies to
better define the mechanisms mediating these complex effects. Finally,
related to its antioxidant effects, iron deprivation may find applications
in the anti-aging field , whether programmed or premature aging and
whether in cosmetics or in gerontology.
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Classical pharmacotherapy usually ends by giving the patient some magic in
the form of a lively , colored , modernly shaped , and shiny pill:
something was missing, something good is being administered. Here we
propose that many diseases as diverse as myocardial infarction or stroke ,
inflammatory conditions such as bleomycin-induced pulmonary fibrosis,
bacterial infections and malaria, or DMD, all of which have a free radical
component, would actually benefit most from taking away - in this case ,
iron. Iron deprivation appears to be more efficient and more feasible than
any classical antioxidant therapy. Indeed , the latter has been limited by
the heterogeneity of the clinical courses of the many diseases in which
oxidative stress plays as role, and by homeostatic mechanisms that
complicate the specificity of tissue and subcellular targeting of
antioxidants. Thus , alternative approaches such as dietary deprivation or
iron chelation are being considered as attractive therapeutic avenues,
more likely to provide both efficient and safe antioxidant protection than
any scavengers, vitamins , or trace elements.

ROS, IRON , AND FERRITIN

ROS include the free radicals , superoxide and hydroxyl , the non-radical
intermediates singlet oxygen and hydrogen peroxide, as well as nitric
oxide and peroxynitrites. At low concentrations , ROS can act as second
messengers, gene regulators , and mediators for cell activation. But under
conditions of excessive production  or reduced availability or efficiency
of antioxidant mechanisms, ROS may accumulate to unbalanced levels and may
then damage almost all cellular components, whether proteins (unfolding,
aggregation , desolubilization , and loss of function) , lipids
(peroxidaton of cell and subcellular membranes), DNA, or mitochondria.
  Iron , although indispensable to the function of many proteins,
including enzymes involved in fundamental processes such as mitochondrial
respiration, plays a major role in oxidative  stress via Fenton chemistry,
where iron (II) , producing OH. Thus , among the ROS , the highly reactive
and extremely toxic OH is produced whenever (and wherever) iron is
available for the Haber-Weiss reaction , which is particularly the case in
the vicinity of DNA or in the mitochondria; indeed, normal cellular
respiration is associated with the production of O2 and H2O2 , thus
providing the substrates, in the presence of iron, for OH generation.
Furthermore, iron contributes to redox cycling of cytoxic compounds such
as Adriamycin or bleomycin, which have a high affinity for DNA. The
central role of iron in oxygen toxicity and the ability of iron
deprivation to prevent OH formation by inhibiting the iron-driven
Haber_Weiss reaction provides a strong rationale for the use of iron
chelators or iron-deficient diets in the prevention of oxidative stress.
  Endogenously, the availability of iron is tightly regulated within
mammalian cells, in particular by the expression of ferritin [2, 3].
Ferritin plays a central role in the cellular protection mechanisms
against iron-mediated oxidative injury, and it has been proposed that
ferritin should be considered as part of the stress protein families [4].
As other stress proteins, ferritin is ubiquitous and highly conserved.
Ferritin specifically binds - "chaparones" - iron, thus protecting cells
from the deleterious consequences of iron-catalyzed free radical
reactions. Ferritin expression is regulated post-transcriptionally by an
iron-dependent mechanism consisting of the cis-acting IRE and trans-acting
IRE binding proteins, IRP1 and IRP2 {2, 3]. In iron-replete cells, IRP1
fulfills the role of a cytostolic aconitase bound to a 4Fe-4S cluster ,
while in iron-depleted cells, IRP1 is associated with ferritin mRNA ,
repressing the translation of ferritin. Transition between the two forms
is regulated by the redox status of the cluster. Interestingly, it has
been suggested recently that at least part of the beneficial effects of
low-dose aspirin in the prevention of artherosclerosis, one of the key
manifestations of oxidative stress in humans, could be related to an
increase in ferritin synthesis in endothelial cells [5].

IRON AND APOPTOSIS

Apoptosis , from the Greek "falling off" (the tree leaves) , is a
sophisticated system for programmed cell death and is involved in a number
of fundamental biological processes such as metamorphosis , embryonic
morphogenesis, development, and removal of superfluous, damaged, or
transformed cells. Apoptosis occurs as a counterpart of proliferation in
growth regulation and has been associated with pathological processes such
as cancer , infections, and chronic inflammation[6, 8]. Apoptosis can be
induced by a large variety of agents , but , regardless of the inducing
agent , the apoptotic process is usually divided into three phases;
induction, control , and executions/degradation , all of which have
distinct biochemical and morphological features [9-11].
  The role of iron in apoptosis remains controversial. In particular, the
relationships between ROS , iron , and apoptosis are complex. On the one
hand , iron contributes to oxidative stress, a well-characterized inducer
of apoptosis [12], and, indeed, iron has, for example, been shown to
accelerate endothelial cell apoptosis via a ROS-dependent mechanism [13].
On the other hand , iron is essential for cell growth and viability, and
leads to an increased expression of antiapoptotic proteins of the Bcl-2
family, and thus, most likely , in at least partial prevention of
apoptosis. It will be of great interest to examine whether iron has the
potential to prevent apoptosis in the case of oxidative stress, or whether
it potentiates it, via an increased generation of OH. With respect to iron
deprivation , most data are in favor of a proapoptotic effect, and it has
been established that indeed it leads to the distinctive morphological
and biochemical features of apoptosis [9, 10, 14, 15]. The phases{s} of
apoptosis in which iron deprivation intervenes is not known, and should
also be the subject of further studies.

TAKING AWAY IRON: WHICH DISEASES MIGHT BENEFIT?

Human beings have evolved a critical equilibrium with iron. Iron
deficiency anemia affects 20% of the world's population , and any "therapy
by taking away" should be followed up with all necessary care so as not to
lead to an aggravation of these numbers. In contrast, the toxic effects of
iron in terms of oxidative injury are best exemplified by the pathology of
patients with primary or secondary hemochromatosis. Hemochromatosis is the
most frequent inherited disease in European populations homozygosity for
the hemochromatosis genes, a recessive trait that leads to iron excess in
tissues, occurs in 0.3% of individuals [16], while hemochromatosis
secondary to hypertransfusion is an iatrogenic model for iron overload. In
both genetically determined and iatrogenic hemochromatosis , the major
complication is cardiac failure. The control of iron levels , by iron
chelators such as desferrioxamine, or more r(HOME)ecently IRCO11 [17], or by
controlled iron deficiency, can prevent oxidative stress and ROS toxicity.
  But the beneficial effects of iron deprivaton are not restricted to
situations of known iron overload, and iron deprivation also represents
an efficient approach for cardio-protection in non-iron-overloaded
organisms. A considerable number of studies , whether in rats , rabbits ,
or dogs, have established the beneficial effects of iron deprivation in
ischemia-reperfusion and post-ischemic damage, whether in the brain or the
heart [reviewed in Ref. 18], which is in agreement with an ROS-dependent
mechanism for reperfusion injury [19].
  Furthermore, beneficial effects of iron deprivation have been
established or suggested in diseases as diverse as anthracycline
dardiotoxicity, organ transplantation, diseases with an inflammatory
component such as bleomycin-induced pulmonary fibrosis, bacterial
infections and malaria, and , more recently, in DMD [18, 20]. All of these
diseases have an oxidative component to their pathogenesis, which suggests
that iron deprivation might be beneficial in many other diseases as well.
One of the most impressive studies on the beneficial effects of "taking
away" reports an 85% prevention of paraplegia secondary to spinal cord
injury in swine [21]. Still another example is Alzheimer disease , in
which iron also represents an essential source of brain oxidative
alterations [22]. Finally, the contribution of iron to the toxic effects
of tobacco smoke on atherosclerosis has not been considered before,
although iron may mediate a great part of the toxicity of tobacco smoke,
whether carcinogenesis or cardiovascular side-effects [23].

IRON IN INFLAMMATION

ROS are among the major mediators of inflammation , and antioxidant
therapy has been proposed in many acute or chronic inflammatory diseases,
although with limited success. Interestingly , although chronic
inflammatory conditions are often associated with iron-deficient anemia,
nutritional iron deficiency has been reported to relieve inflammation in a
number of these conditions, in particular in adjuvant-induced joint
inflammation [24]. Iron-deficient diet has been shown to decrease
inflammation significantly in bleomycin-induced pulmonary fibrosis in
hamsters [25], a condition mediated by ROS and in particular OH , and by
TNF. Like anthracyclines, bleomycin has high affinity for DNA and enters
iron-dependent oxidation-reduction dycles, generating high levels of OH,
while at the same time activating NF-kB, as reflected by TNF release by
alveolar macrophages, thus preventing apoptosis of intrapulmonary
inflammatory cells.
  The outcome of inflammation strongly depends upon the apoptosis of the
inflammatory cells [8, 11]. Thus, since iron deprivation increases
apoptosis, its beneficial effects on inflammation could depend upon dual
target mechanisms: prevention of oxidative damage on the one hand, and
promotion of apoptosis on the other. Iron deprivation may also exert more
specific beneficial effects on the immune response leading to
inflammation, such as blocking interleukin-2 receptor expression on T
lymphocytes, thus controlling T cell proliferation [26].

IRON AND INFECTIOUS DISEASES

Iron removal may have distinct therapeutic effects in bacterial
infections. Indeed , iron is an indispensable nutrient for many bacteria,
to the point that bacteria have evolved mechanisms to acquire and secure
iron from host cells during host-pathogen interactions [27].
Myocobacteria, whether tuberculosis or paratuberculosis, are paradigmatic
for such requirements. The multiplication of the bacteria appears greatly
enhanced within iron-replete macrophages , whether murine [28] or human
(Boshoff T, Bachelet M, Polla BS and Bornman L, unpublished results). Iron
levels of the host thus appear as an essential determinant in the outcome
of infectious disease. In humans, this has been particularly well studied
for tuberculosis. Indeed, a relationship between death from tuberculosis
and iron overload of the liver and mononuclear-macrophage system (the
latter having the strongest association) has been established [29], based
on observations from the early twentieth century on iron overload in South
African blacks [30]. This condition appears to result from an interaction
between the amount of dietary iron and a gene distinct from the HLA-linked
iron-loading locus responsible for hereditary hemochromatosis, and has
been proposed as an essential component of the increased incidence of
tuberculosis in South Africa.
  Further supporting a role for iron in bacterial virulence, nutritional
iron deficiency attenuates Salmonella typhimurium infection in mice as
compared with both iron-substituted and normal diet control animals [31].
In malaria, iron deprivation might exert dual beneficial effects, by
acting both on the plasmodium itself and on the syndromes caused by the
infection, in which ROS-dependent mechanisms again play a key role [32].
In candidiasis, iron deprivation has been shown to restore antifungal
effector functions of phagocytic cells [33].
  In light of these data , although scarce as yet , the possibilty that
moderate iron deprivation may represent an additional approach for the
limitation of pathogenicity and spreading of infectious disease, including
AIDS, should be carefully considered.

IRON DEPRIVATION IN DMD

DMD is a severe genetic disorder due to mutations in the dystrophin gene
at Xp21, which prevent the expression of this cytoskeletal ,
membrane-associated protein in affected individuals , leading to
progressive muscle wasting [45]. While the absence of dystrophin is
clearly responsible for the DMD phenotype, the exact role of its
deficiency in the pathobiochemistry of DMD has remained elusive. One of
the approaches taken in several studies to the pathogenesis of DMD has
been to consider free radical reactions. Classical antioxidant therapeutic
trials , however , have been inconclusive. We thus hypothesized that iron
removal may provide a useful starting point for controlling free radical
reactions in DMD. This hypothesis was tested in the murine model for DMD,
the mdx C57BL/10ScSc inbred mice [35], which are genetically homolgous to
DMD. Although the use of desferrioxamine has been proposed for DMD before
[36] , we tested dietary iron deprivation as the method of choice for
decreasing iron levels, because chelating agents such as desferrioxamine 
might exert specific effects distinct from iron deprivation. The results
were reported by Bornman et al. [20]: there is a significant decrease in
necrotic fibers in iron-deprived mdx mice, which may imply that the
iron-driven generation of OH does indeed play a role in necrosis of
dystrophin-deficient muscle fibers and the consequent attraction of
inflammatory cells. This reduction in muscle necrosis in the mdx mouse
following iron deprivation provides a basis for new approaches in the
treatment of DMD patients , which is particularly exciting because of the
lack of therapy for DMD and the  current failure of a timely application
of gene therapy. Something as simple as iron deprivation should be
examined without delay in other animal models as well in clinical trials ,
in all myopthies with an oxidative component including those in which
classical antioxidants have not proven efficient [37, 38]

IRON DEPRIVATION AS AN ANTI-AGING FACTOR

Cellular , tissue, and organismal aging has been convincingly associated
with a progressive oxidant/antioxidant imbalance , and decreasing
oxidative stress together with increasing antioxidant defenses has
provided the source for most 'fountains of youth'. 
  The increased longevity of woman as compared with men has been proposed
to be related to behavioral components such as a lower exposure to sources
of oxidants including tobacco smoke. I would like to propose here that
this evolutionary advantage rather relates to chronic iron deficiency in
women during their reproductive life, secondary to menstruation,
pregnancies and deliveries. If indeed oxidative stress and progressive
oxidant/antioxidant imbalance is a major component of aging , then iron
deprivation might prevent much of the cellular, tissue, and organismal
lesions associated with aging and contribute to successful aging. [39]
  Skin aging , a most efficient witness of general premature aging, also
presents as an oxidant/antioxidant imbalance, favored by UV radiation
exposure [40]. Iron is involved in UV-induced connective tissue
degradation and DNA damage [41, 42], and the possibility that moderate
iron deprivation might protect skin from UV-induced premature aging and
cancer should thus be considered both in experimental animal models and in
human cosmetic pharmacotherapy.
  If our hypothesis holds true, moderate iron deprivation might shortly
add to other anti-aging "miracles" such as fruits and vegetables ,
supplementation in vitamin E , selenium , and others, and increase
individual potential for successful aging, whether skin or organismal
aging.

CONCLUSION

In conclusion, therapy by taking away (iron) has a great potential for
many different diseases, all of which share ROS-mediated mechanisms. The
development of new, non-toxic , easily administrable iron chelators such
as IRCO11 may shortly become the most efficient and fashionable
antioxidant, anti-aging, anti-infectious, and anti-inflammatroy therapy.
In the meantime, although taking away by controlled dietary deprivation is
less attractive , it should be considered in all of the above, as well as
in the currently incurable, devastating genetic or acquired myopathies
such as DMD.




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