CIPYP   05508
CENTRO DE INVESTIGACIONES SOBRE PORFIRINAS Y PORFIRIAS
Unidad Ejecutora - UE
capítulos de libros
Título:
Preface
Autor/es:
BATLLE, ALCIRA; ROSSETTI, MARIA VICTORIA
Libro:
PORPHYRIAS AND ASSOCIATED PATHOLOGIES. BIOCHEMISTRY AND MOLECULAR BIOLOGY CELLULAR AND MOLECULAR BIOLOGY, VOL. 55, PART II
Editorial:
CMB edition
Referencias:
Lugar: Noisy Le Grand; Año: 2009; p. 1 - 7
Resumen:
To begin with, we wish to thank again
Professor Dr. Raymond Wegmann The Founding
President and Professor Dr. Jean-Michel
Maixent, The President, Editors-in-Chief of
Cellular and Molecular BiologyTM for their
generous invitation to become Guest- Editor and
Co-Guest Editor of this special theme issue on
Porphyrias and associated pathologies.
Biochemistry and Molecular Biology, which has
been published in two Volumes, Part I, appeared
in February 16 th, 2009 and now, Part II, scheduled
for July 1 st 2009.
Although Cellular and Molecular BiologyTM
has already published three others special issues on
this subject, one in 1997, and two in January and
December 2002,
to have another issue on
Porphyrins and Porphyrias is not too much,
since it belongs to one of the modern problems for
which orphan drugs are requested
(quoted
from Professor Dr. Raymond Wegmann, Cellular
and Molecular BiologyTM, , 2002, 48, 823).
We also wish to thank again Mr Mourad
Fares, Executive Editor of CMB, for his support,
composition and editing of the papers.
The articles put together in Part II of this
theme issue, come from the highest experts in the
world in this field, biologists, physicians, chemists,
physics, all of them leading porphyrinologists,
which will assure, to make Part II as well as it was
with Part I, a highly important reference issue for
the future. Therefore we are also deeply thankful to
all the authors for their contributions and most
important for their collaboration in making
possible the production of this theme CMB issue
on Porphyrias and associated pathologies.
Biochemistry and Molecular Biology
Porphyrins and Porphyrias, since the middle
of the 50s, porphyrinologists from all over the
world have been meeting at least once or later
more than once a year, mostly in Europe and USA,
to discuss about the latest innovative results on the
biochemistry, molecular biology, regulation and
functional mechanisms of the enzymes involved at
each step of the porphyrins biosynthesis, which
have been isolated, cloned and even chrystalized,
and its related diseases: the Porphyrias.
In 1997, Professor Robert Aquaron, attempted
to list a number of the International Porphyrins and
Porphyrias Meetings, mostly hold in Europe, since
1955, until then. However we should also recall
and include the Gordon Research Conferences,
started in 1968, occurring in USA, every two
years ( about 22) which were just mentioned as
well as the Tetrapyrrole Discussion Group
Meetings, gathering somewhere in Europe, much
more often in UK, every nine months since 1967
(by now there have been about 33 meetings).
Porphyrins and Porphyrias, certainly, one of
the most important and endless theme for
discussion. Some of us have had the honour and
pleasure of having been closely associated, known
and being personally involved in Porphyrins and
Porphyrias research for nearly 50 years by now,
also having had the pionners in this field as our
mentors, something to celebrate, so we will, after
reading this special issue of CMB.
Porphyrins synthesis is one of the most
fundamental attributes of all living cells.
Central to the fundamental processes of
photosynthesis and respiration, are chlorophylls
and haem, respectively, which are porphyrins,
that is the reason why, Lemberg and Ledge in
1949, coined the expression porphyrins are the
pigments of life, could it be anything more
important than that?.
We would wish to partially quote one of us
(Batlle, CMB TM, 2002, 48, 823), when saying that
porphyrins are unique and intriguing molecules,
historically having a geologic and a biologic
medical chapter. The former going back many
millions of years, when the formation of
porphyrin-like compounds and porphyrins was
contemporary with the development of life on
earth. The latter started at the beginning of
nineteen century when iron-free hematin was
obtained by Scherer in 1941, after treating dried blood with concentrated sulphuric acid. This
pigment was later purified by Thudichum in 1867,
who named it cruentine and described for the
first time its splendid blood-red fluorescence.
The term porphyrin was soon after coined by
Hoppe Seyler in 1871.
As already stated, porphyrin biosynthesis is
one of the most fundamental attributes of all living
cells. Classical isotope tracer studies from the
laboratories of Shemin, Rimington, Granick and
Neuberger, identified the precursors and
intermediates in the haem biosynthetic pathway
marking the beginning of a whole new field of
research in the biogenesis of these pigments.
Then, most of the eight enzymatic steps involved
were identified. Today all the enzymes have been
cloned and sequenced and most of them have also
been crystallized.
The porphyrin pathway is very finelly
controlled. In most tissues and species,
Aminolevulic Acid Synthetase (ALA-S) is the
regulatory enzyme. Regulation occurs by feed back
inhibition of ALA-S, so haem deficiency, owing to
blocking the pathway at some step, as it happens in
the Porphyrias, releases this inhibition. The term
porphyria, gradually emerged after
Stokvis(1889) reporting the death of an elderly
women, excreting dark red urine after having
received sulfonal.
Human porphyrias are specific inherited or
acquired defects, each representing a partial failure
of one of the seven enzymes beyond ALA-S and
they are characterised by a typical excretion
pattern of porphyrin intermediates.
We would like to recall that porphyrins are the
only photosensitizers synthesized in the cells and
the best examples of these endogenous sensitizers
are the porphyrin intermediates formed and
accumulated in the cutaneous porphyrias,
producing the characteristic skin
photosensitization.
Photodynamic Therapy (PDT) is a promising
new modality of cancer treatment, which involves
the combination of a photosensitizing agent, which
is taken up selectively and retained by tumoural
cells, and light of an appropriate wavelength.
Separately, each of these factors is harmless by
itself, though, when combined, in the presence of
oxygen, cytotoxic reactive oxygen species are
produced, leading to irreversible cellular damage,
causing cell death and tumor destruction.
After either exogenous administration or
endogenous synthesis, porphyrins finally
accumulate in higher proliferative cells. Light
energy absorbed by the photosensitizer (PS) can
produce fluorescence. The tumour localizing
properties of the PS have been extensively
employed for the Photodetection (PD) and
diagnosis, as well as for the PDT of tumours.
Photodynamic properties of porphyrins are a
well known characteristic of these compounds. As
already stated, a clear demonstration of their
powerful photosensitizing properties, can be seen
in the cutaneous porphyrias, where abnormal
quantities of circulating porphyrins result in the
typical skin photosensitivity.
One of the main developments in PDT, has
been the novel approach using the precursor 5-
Aminolevulinic Acid (ALA), leading to the
endogenous synthesis of the active photosensitizer
(PS) Protoporphyrin IX (PPIX), the so called ALA
based PDT or ALA-PDT.
Besides PPIX, other PSs have been
synthesized or extracted from natural products, to
be used in PD or PDT.
In the paper Endogenous and exogenous
Porphyrins as Photosensitizers in the HEP-2
Human Carcinoma Cell Line by M.G.Alvarez,
N.E. Milanesio, V. Rivarola, E. Durantini, A.
Battle and H. Fukuda, the photodynamic activity of
three PSs: ALA-induced PPIX, the porphyrin
derivative 5-(4-trimethylammoniumphenyl)-10, 5,
20-tris (2,4,6-trimethoxyphenyl) porphyrin (CP)
and the molecular dyad porphyrin-C60 (P-C60),
the last two incorporated into liposomal vesicles,
was evaluated on Hep-2 human larynx carcinoma
cell line.
When photosensitized with ALA and P-C60,
chromatine condensation characteristic of
apoptotic cell death was found; instead, 58 % of
necrotic cells were observed with CP. The results
show that in the Hep-2 cells, of the three PSs
analyzed, the molecular dyad P-C60 was more
efficient than CP and PPIX, and confirm that PDT
can induce different mechanisms of cell death
depending on the PS and the irradiation dose.
In the next paper ROS production by
endogenously generated Protoporphyrin IX in
murine leukemia cells, by B. Diez, R. Cordo
Russo, M.J. Teijo, S. Hajos, A. Batlle and H.
Fukuda, they studied the efficiency of PpIX
synthetized from ALA on ROS generation, in the
Vincristine resistant (LBR-V160), Doxorubicin
resistant (LBR-D160) and sensitive (LBR-) murine
leukemia cell lines. Cells were incubated with 1
mM ALA and then irradiated during different
times with fluorescent light. Then, production of
ROS was analyzed by flow cytometry using
different fluorescent probes. It was found that superoxide anion
production in the three cell lines increased with
irradiation time whereas no peroxide hydrogen was
detected. Mitochondrial damage also increased in
an irradiation time dependent manner, being higher
in the Vincristine resistant line. Because the
apoptotic cell death increased with irradiation time,
the authors have shown that ROS are critical in
ALA-PDT efficiency to kill malignant cells.
Clinical manifestation of porphyrias are often
associated with exposure to precipitating agents,
including polyhalogenated aromatic hydrocarbons,
alcohol abuse, estrogens and steroids ingestion,
stress and infection with Hepatitis C virus (HCV),
less frequently, Hepatitis B virus (HBV). and
association with infection with the Human
Immunodeficiency virus (HIV).
The role that steroids play in the expression
of housekeeping 5-Aminolevulic Acid Synthetase
(ALA-S1) has been the subject of scrutiny for a
number of years. The very earlier studies from
Granick and others, showed that in addition to a
female preponderance of acute attacks, numerous
steroids of both natural and pharmaceutical origins
could be linked to induction of attacks and to
changes in the activity of ALA-S. In the paper
Functional analysis of the 5 regulatory region of
the 5-aminolevulinate synthase (ALAS1) gene in
response to estrogen BY N. du Plessis, M
Kimberg, M G Zaahl, A Sadie, M Venter, L van
der Merwe, A Louw & L Warnich, the authors
investigated some factors influencing the clinical
expression of porphyrias, primarily by altering the
rate of heme synthesis. To date, no genotypephenotype
correlation has been made to explain the
variable penetrance observed in variegate
porphyria (VP) and other acute hepatic porphyrias.
As first and rate determining gene in the heme
pathway, ALAS1, appears to be an ideal candidate
modifier. Previous studies established critical
mechanisms for ALAS1 regulation and a direct
transcriptional response to drugs by defined drugresponsive
enhancer sequences. They evaluated the
effects of a possible oestrogen binding receptor at
the five-prime end of ALAS1 gene. Its role appears
to be in increasing the transcriptional response
when oestradiol is present.
It is also known that in some porphyrias, mild
to moderate hepatic iron overload plays a key role
in its pathogenesis. Hemochromatosis is the
commonest cause of primary iron overload and
some mutations in the hemochromatosis gene
(HFE), associated with hereditary
Hemochromatosis, have been found to be more
frequent in PCT.
M.V. Rossetti, M. Méndez, S. Afonso, E.
Gerez, A. Batlle, A. Muñoz and V. Parera in their
paper HFE gene mutations in patients with
altered iron metabolism in Argentina have
investigated the prevalence of C282Y, H63D and
S65C mutations in 95 individuals bearing iron
metabolism alterations to establish an early
diagnosis of Hereditary Hemochromatosis (HH).
Among this population, 58% carried mutations in
the HFE gene. H63D mutation was found in 32.6%
of the subjects (29.5% in heterozygocity, 3.15% in
homozygocity). S65C mutation was only detected
in the heterozygous form (5.3% of the patients), 2
of them carried also H63D mutation. C282Y in
heterozygocity was found in 15.8% of the
individuals. Their findings were consistent with the
Mediterranean origins of the population of
Argentina, where the commonest mutation was
H63D.
Association of porphyrias with other
pathologies, such as diabetes, lupus, leukaemia,
Hansens disease, cancer and autism has been
reported. There is also association of porphyrias
with the treatments used for other pathologies,
such as estrogen-therapy in prostate cancer and
hemodialysis in patients with renal failure.
Porphyrias are often multifactorial, therefore,
knowledge of all risk or etiological factors in each
patient is most important for the management of
the disease.
The paper Association between Porphyria
Cutanea Tarda and Beta Thalassemia Major By
L. Barbieri, A. Macri, G.L. Palmieri, C. Aurizi and
G. Biolcati, describes the first two cases of
porphyria cutanea tarda (PCT) associated with
beta-thalassemia major. The clinical course of two
female patients affected by beta-thalassemia major
was complicated by the onset of PCT. Both
patients were also suffering from hepatitis C virus
infection, iron overload and anaemia. The authors
discuss about the role performed by some of these
conditions in triggering overt PCT. An
improvement of the clinical and biochemical
picture of PCT was obtained with chloroquine
therapy.
Porphyria cutanea tarda (PCT) is caused by
inhibition of uroporphyrinogen decarboxylase
(URO-D) activity in hepatocytes. Subnormal
URO-D activity results in accumulation and
urinary excretion of highly carboxylated
porphyrins, uroporphyrin and heptacarboxyl
porphyrin. Heterozygosity for mutations in the
URO-D gene can be found in the familial form of
PCT (F-PCT). Over 70 mutations of URO-D have
been described so far, but very few have been
characterized structurally. In the paper Structural and kinetic characterization of mutant human
uroporphyrinogen decarboxylases, C. A. Warby,
J. D. Phillips, H. A. Bergonia, F. G. Whitby, C. P.
Hill, and J. P. Kushner, characterized 3 mutations
in the URO-D gene found in patients with F-PCT.
G318R, K297N and D306Y mutations. Expression
of the D306Y mutation resulted in an insoluble
recombinant protein. G318R and K297N have
little effect on the structure or activity of
recombinant URO-D, but the proteins displayed
reduced stability in vitro.
A number of murine models of PCT centered
around the administration of iron and compounds
that induce transcription of cytochrome P450s have
been developed. So, the influence of porphyrins
and porphyrinogens themselves on metabolic
alterations in hepatocytes has been difficult to
distinguish from the effects of the compounds
precipitating the porphyric state. The Utah team
had previously developed a genetic murine model
of PCT by crossing porphyria-susceptible Urod+/-
mice with mice homozygous for deletion of the
hemochromatosis gene (Hfe). The Urod+/-, Hfe-/-
mouse spontaneously develops uroporphyria and
allows studying the effects of porphyrinogen and
porphyrin accumulation on enzymes and
transporters involved in tetrapyrrole disposition
without the confounding effects of exogenous
factors. In their paper "Longitudinal Study of a
Mouse Model of Familial Porphyria Cutanea
Tarda", D-D.Arch, H.A. Bergonia, L. Hathaway, J.
P. Kushner, J.D. Phillips and M.R. Franklin,
describe for the first time, a longitudinal study of
Urod+/-, Hfe-/- from 8 weeks to 1 year.
The authors have shown that the first sigh of
abnormal porphyrin biosynthesis in the Urod+/-,