The Role of Erythropoietin and its Receptor in the
Immune, Central Nervous and Cardiovascular Systems
Katarzyna
Aleksandra Lisowska
Katarzyna
Aleksandra Lisowska, Department of Pathophysiology, Medical University of Gdańsk,
Dębinki 7, 80-211 Gdańsk, Poland
Correspondence to: Katarzyna
Aleksandra Lisowska, Department of Pathophysiology, Medical University of Gdańsk,
Dębinki 7, 80-211 Gdańsk, Poland
Email: katlis@gumed.edu.pl
Telephone: +48583491510
Received: March 5,
2015
Revised: April 16, 2015
Accepted: April 21, 2015
Published online: July 6, 2015
ABSTRACT
Primary role of
erythropoietin (EPO) is to protect red blood cell progenitors from apoptosis
and to stimulate their growth and differentiation by binding to its receptor
(EPOR). However, the expression of EPOR has been identified on other human
cells, such as granulocytes, monocytes, lymphocytes, endothelial cells and
neurons. Its presence on these cells suggests that beyond erythropoietic
function EPO might have some other properties. Various studies show that
recombinant human erythropoietin (rhEPO) used in the treatment of anemia
associated with chronic kidney disease (CKD) has potentially beneficial
influence on cellular processes such as proliferation and apoptosis of cells
other than erythrocyte progenitors. It can modulate the activity of immune cells,
protect neurons from apoptosis and even stimulate angiogenesis, but also it has
a pro-thrombotic properties. This review presents current knowledge on the role
of EPO and its receptor in the immune, central nervous and cardiovascular
systems in various pathophysiological situations.
© 2015 ACT. All
rights reserved.
Key words: Erythropoietin, Erythropoietin
Receptor, Lymphocytes, Neurons, Endothelial Cells, Apoptosis, Neuroprotection
Lisowska KA. The Role of
Erythropoietin and its Receptor in the Immune, Central Nervous and
Cardiovascular Systems. International
Journal of Hematology Research 2015; 1(2): 42-51 Available from: URL:
http://www.ghrnet.org/index.php/ijhr/article/view/1099
INTRODUCTION
Interest in erythropoietin (EPO) reaches late 80s, when its recombinant
analogue has been approved by the US Food and Drug Administration for the
treatment for anemia in patients suffering from chronic kidney disease (CKD).
In healthy people, EPO is produced in peritubular capillary epithelial kidney
cells under hypoxic conditions[1]. It is not stored in kidneys and
therefore requires activation of gene expression. The sequence preceding the
EPO gene promoter is characterized by the presence of DNA sequences which
determine its tissue specificity (KIE – kidney inducible element, NRE –
negative regulatory element)[2]. Enhancer sequence responsible for
the hypoxia-dependent expression of EPO gene is located at its 3’ end where
HIF-1 (hypoxia inducible factor 1) and HNF-4 (hepatocyte nuclear factor 4) bind[2].
HIF-1 is a heterodimer composed of two subunits: HIF-1α and HIF-1β[3],
activity of which is regulated posttranscriptionally[4]. Under
normal oxygen concentration, HIF-1α subunit is modified by an oxidative α-prolyl
hydroxylase, which allows attachment of ubiquitin ligase complex, degradation
of HIF-1α and thereby inhibition of the synthesis of EPO. In hypoxic
conditions, the enzyme is inactive, which allows to create complex of HIF-1α
and HIF-1β that binds to the enhancer sequence and initiates EPO gene
transcription[3,5]. EPO produced in the kidney passes to the blood
plasma and then to the bone marrow, where it protects erythroid progenitors
from apoptosis and promotes their proliferation and differentiation by binding
to its receptor (EPOR) on cells at the BFU-E (erythroid burst-forming unit) and
CFU-E (erythroid colony-forming unit) stages of erythropoiesis[6].
EPO binding to EPOR results in receptor homodimerization followed by an
activation of JAK (Janus kinase) family members[7] and
phosphorylation of several signaling proteins, including signal transducer and
activator of transcription 5 (STAT5)[8], phosphatidylinositol
3-kinase (PI-3K)[9], protein kinase C (PKC)[10] and
mitogen-activated protein kinase (MAPK)[11] (Figure 1).
Erythropoietin
was isolated from urine of patients with pernicious anemia in 1977[12].
This step allowed for the cloning of the gene encoding EPO, which was achieved
by Lin and Jacobs in 1985[13,14]. Two years later Eschbach et al[15]
presented the results of phase I and II of clinical trials with recombinant
human erythropoietin (rhEPO), which showed an increase in hematocrit in
patients with end-stage renal disease (ESRD). Principles of treatment of anemia
with rhEPO in ESRD patients were defined for the first time in 2000[16]
and, currently, specific recommendations for the use of rhEPO are updated by
ERBP (European Renal Best Practice) and NKF DOQI (National Kidney Foundation
Dialysis Outcomes Quality Initiative). Since the introduction of the drug, many
articles describing other, beyond correction of anemia, positive effects of
rhEPO therapy have been published. This was related to, among other things, the
discovery of receptor expression in cells other than erythroid progenitors,
including polymorphonuclear leukocytes (PMNLs)[17], monocytes and
lymphocytes[18], endothelial cells[19,20], neurons[21,22]
and some tumors cells[23]. Multiple studies suggest that rhEPO/EPO
can protect brain tissue from hypoxic damage or prevent ischemia-reperfusion
myocardial injury, stimulate angiogenesis and modulate immune responses.
However, its exact effect on these cells is not as clear as its role in
erythropoiesis.
Role of
erythropoietin and its receptor in modulating immune responses
Anemia in ESRD patients is mainly a consequence of kidney damage,
although several other factors, including chronic blood loss, iron deficiency
and presence of pro-inflammatory cytokines also affects its development. In
addition to the disturbances in water and electrolyte balance, acid-base
balance, calcium-phosphate or hormonal balance, these patients also present
defects in both innate and acquired immunity resulting in an increased
susceptibility to infections, which are a frequent cause of death, especially
among hemodialyzed (HD) patients[24]. Studies have shown that the
complement system components and immune cells, especially neutrophils and
macrophages, are activated when blood flows through the dialyzer, which leads
to the release of large amounts of pro-inflammatory cytokines, mainly
interleukin (IL-) 1, IL-6 and tumor necrosis factor alpha (TNF-α)[25].
Moreover, CD4+ T lymphocytes from HD patients are characterized by a
reduced expression of key surface antigens (especially co-stimulatory CD28 and
activation markers: CD69 and CD25), impaired proliferation parameters
(decreased percentage of proliferating cells and number of divisions, long
period of time required to enter the first phase of cell cycle) and a decreased
production of a key cytokine IL-2 in response to stimulation with mitogen[26,27].
Since the function of B cells largely depends on the activation of CD4
lymphocytes, their impaired activity can support the progression of immune
deficiency manifested as the reduced response of HD patients to vaccination
against hepatitis B[28] and frequent infections[24]. In
the late 90's, first publications describing the effect of treatment with rhEPO
on immunological parameters in patients on dialysis have been published.
Studies showed an increase of IL-2 concentration after stimulation of whole
blood cells cultures of HD patients with phytohemagglutinin (PHA) as well as
with rhEPO in the same concentration as the physiological concentration of EPO
in blood, which is 0.05 U/mL[29,30]. After few months of rhEPO
therapy decreased production of pro-inflammatory cytokines (IL-6 and TNF-α) and
elevated secretion of anti-inflammatory IL-10 in whole blood cell cultures
stimulated with PHA were also observed[30,31]. There were also
studies showing higher concentration of TNF-α in serum of HD patients receiving
rhEPO[32] but its level was determined after the dialysis procedure,
during which the release of large amount of pro-inflammatory cytokines occurs[25].
Bryl et al[29,31] and Trzonkowski et al[30]
demonstrated that rhEPO acts directly on production of cytokines by whole blood
cells in vitro. It has also been demonstrated that rhEPO directly
enhances B lymphocytes antibody (IgG, IgM and IgA) production in serum-free
medium[33]. However, at that time some authors suggested that
rhEPO-induced immunomodulation is mainly dependent on general improvement of
patients’ condition after few months of rhEPO treatment because an elevation of
hematological parameters is accompanied by a simultaneous increase in the
number naive T lymphocytes[34].
Expression of
EPOR on the surface of granulocytes was first described more than a decade ago
pointing towards a possible role of EPO and its receptor in the immune
responses. Sela et al[17] and Kristal et al[35]
showed that there is a strong positive correlation between the percentage of
EPOR-positive cells and the level of EPO in the serum which suggested that
presence of hormone up-regulates the expression of receptor. Moreover,
following few weeks of rhEPO treatment, in HD patients, the rate of superoxide
release from granulocytes fell significantly when compared with the
pretreatment values. Authors concluded that rhEPO reduces the extent of
inflammation by interaction with granulocytes through the receptor present on
their cell surface. Similar results were obtained in patients on continuous
ambulatory peritoneal dialysis (CAPD)[36] and ESRD patients not
treated with renal replacement therapy[37]; in vitro,
incubation of granulocytes from CAPD patients with increasing concentration of
rhEPO also resulted in a significant reduction superoxide release.
EPOR belongs
to the same family of type I cytokine receptors as IL-2, IL-4, IL-6, IL-7,
IL-12, IL-13 or GM-CSF (Figure 2), which transmit signals through JAK-STAT
pathway using common signaling chain[38]. It has been demonstrated
that IL-2 as well as rhEPO stimulate STAT5 by inducing phosphorylation of the
same tyrosine residue and that these IL-2- and EPO-induced STATs have an
identical DNA binding specificity and immunoreactivity[39]. Some
other studies have revealed activation of specific pathway containing STAT5 in
EPOR-transfected lymphoid cell line by rhEPO which suggested that lymphocytes
could contain a machinery necessary for signal transduction from this receptor[40].
Therefore, using molecular methods and quantitative flow cytometry, few years
ago we tested whether peripheral blood mononuclear cells (PBMCs) express EPOR.
Our studies have shown that every PBMC type tested ex vivo (CD4+ and
CD8+ T lymphocytes, B lymphocytes and monocytes) demonstrate some
basic level of EPOR expression with the CD4+ cells presenting the
lowest (about 50-100) number of receptor molecules per cell on their surface[18].
At the same time we observed low percentage of lymphocytes expressing very high
number of EPOR reaching about 1500 molecules per cell[18]. Our
further studies have shown that, although the level of EPOR on the surface of
CD4+ cells is very low, stimulation with an immobilized monoclonal
anti-CD3 antibody results in its increase to a value as high as 1000 molecules
per cell[18,41] which is reported to be typical for the most
immature erythroid cells[42]. Our findings were also confirmed by
other authors; Spaan et al[43] showed that human monocytes
not only express EPOR mRNA, but also are responsive to rhEPO in a cell culture.
In vitro, exposure of PBMC from individuals to rhEPO in the presence of
lipopolysacccharide (LPS) showed a significant reduction of monocytes producing
pro-inflammatory cytokines[43]. Last year, Cravedi et al[44]
have published results which confirmed that resting CD4+ and CD8+
cells express low level of EPOR on their surface but its expression is
up-regulated after few days of stimulation with anti-CD3 and anti-CD28
antibodies. EPOR up-regulation on T lymphocytes is probably, at least in part,
a consequence of an increased EPOR gene expression[44,45] which
seems to be dependent on the expression of specific transcription factors[45].
This raises the question about the role
of the receptor for erythropoiesis-stimulating hormone in the cells of the
immune system. Various studies show that the presence of rhEPO in the culture
of mononuclear cells modulates the levels of pro- and anti-inflammatory
cytokines produced by either monocytes or lymphocytes[29-31,46]. It
seems that rhEPO itself does not influence T lymphocytes proliferation, at
least not directly[34]. However, according to Cravedi et al[44],
rhEPO inhibits expansion and proliferation of T lymphocytes by uncoupling IL-2R
signaling in vitro. In their studies, rhEPO inhibited phosphorylation of
PI-3K-AKT signaling pathway without affecting STAT5, while our studies have
shown that rhEPO in low doses stimulates phosphorylation of STAT5 depending on
stimulation through T cell receptor (TCR)/CD3 complex[41]. Different
results seem to be largely dependent on the doses of rhEPO used in vitro
– we used a concentrations similar to the physiological concentration of EPO in
blood serum (0.1, 0.5 U/mL), while Cravedi et al. used a very high doses
(1,000-2,000 U/mL). This shows how the experimental design can affect the
results of research. On the other hand, observation that rhEPO is able to
inhibit expansion of T lymphocytes in response to polyclonal stimulation would
explain its protective effects in kidney transplant recipients[47].
This may be one of the factors, in addition to correction of hemoglobin levels
during rhEPO therapy, that support prolonged graft survival and slow down the
progression of chronic graft nephropathy. Experiments performed using animal
model showed that treatment with rhEPO, not the normalization of
post-transplant hemoglobin levels by blood transfusions, prevents chronic renal
allograft injury[48].
In HD
patients, rhEPO therapy lasting for at least several months not only corrects
the anemia state but also normalizes activation phenotype of CD4+ T
lymphocytes and their proliferative capacity[26]. It is associated,
among other things, with the increased expression of CD28 and CD69 antigens on
lymphocytes’ surface[26]. Surface antigens not only are involved in
maintaining contact between T lymphocytes and other cells, including B cells
(for example, through CD40L antigen) or antigen presenting cells (APCs), but
also influence proliferation and cytokine production. CD28, for example,
regulates IL-2 production on the transcriptional level[49]; its
lower expression on CD4+ cells would explain reduced levels of IL-2
in response to mitogenic stimulation in HD patients[29,30]. At the
same time, expression of antigens depends on many factors, including the level
of various cytokines secreted by lymphocytes themselves and other cells in
their area. A good example is the relationship between the level of CD28 expression
on T lymphocytes and the level of TNF-α, which was shown to regulate
transcription of CD28 gene directly[50]. Chronically high levels of
TNF in HD patients could therefore reduce the level of CD28 on CD4+
cells, which in turn would lead to a reduction in the concentration of IL-2.
Our studies demonstrated that in vitro incubation of activated PBMCs of
HD patients with rhEPO in a concentration similar to the physiological (0.1
U/mL) decreased the level of TNF- while increasing the levels of IFN- and IL-10[46]. However,
similar experiment carried out in a group of healthy people showed no changes
in Th1 or Th2 cytokine levels when rhEPO was added to cell culture. It means
that effect of rhEPO is dependent on the initial concentration of cytokines in
an individual; the level of TNF- was decreased while the level of IL-10 and IFN- was increased in
healthy people compared to HD patients[46]. In our opinion,
long-term rhEPO administration could regulate the functioning of immune cells
of ESRD patients on chronic dialysis (Figure 3). Although the mechanism of
action of rhEPO on T lymphocytes is still unclear, it seems that their improved
(normalized) phenotype and proliferation capacity in HD patients depends mainly
on changes in the concentrations of pro- and anti-inflammatory cytokines, which
can be regulated by the presence of relevant concentrations of EPO in the
serum. Our own studies[18,39] and results of Cravedi et al[44]
have shown that the presence of rhEPO may affect the activity of various
signaling molecules (e.g., JAK2, AKT or STAT5) in human T lymphocytes
stimulated through the CD3/TCR complex in a dose dependent manner and its role
in the modulation of T cell activity is probably also related to the number of
EPOR molecules on their surface. However, further studies are required in order
to explore the mechanisms of the impact of EPO on T lymphocytes.
Erythropoietin and its receptor in the
cardiovascular system
Much more is known about potential role of erythropoietin in human
cardiovascular system. Many studies show that administration of rhEPO may have
an important impact on the development of hypertension by increasing viscosity,
vasoconsctriction and enhancing vascular reactivity. However, at the same time
it seems that EPO/rhEPO can protect the myocardium against ischemia-induced
damage.
The
relationship between the endothelium and hematopoiesis has been known since the
90s, when it was shown that endothelial cells produce proteins which support
growth and differentiation of BFU-E and CFU-E colonies[51]. In 1990,
Anagnostou et al[20] showed that endothelial cells have on
their surface about 30000 molecules of EPOR per cell. Studies of EPOR
expression on erythroid progenitors and activated T lymphocytes have shown only
a small number of surface receptors (usually about 1,000 molecules per cell).
However, different authors speculated that receptors present on erythroid
progenitor cells have high affinity for EPO which is sufficient for its differentiating
effect on these cells despite the small number of receptor molecules on their
surface[52,53]. Anagnostou et al[20] showed that
endothelial cells express a high number of relatively low-affinity receptors
and demonstrated that rhEPO at the concentration of 5 to 20 U/mL enhances the
migration of endothelial cells and stimulates their proliferation (Table 1).
Studies
performed in patients with advanced renal failure and in healthy individuals
have also shown that rhEPO can regulate proliferation and differentiation of
endothelial progenitor cells (EPCs)[54,55]. These authors
demonstrated that the number of circulating peripheral blood hematopoietic
progenitor cells increases, especially at the beginning of rhEPO treatment with
a standard therapeutic dose[54]. In vitro, the effect of
rhEPO on EPCs was dose-dependent and led to the activation of the AKT signaling
pathway and enhanced formation of tube-like structures[54,55].
George et al[56] partly confirmed their observations
examining the effect of chronic treatment with rhEPO on the numbers and
functional properties of EPCs in patients with congestive heart failure (CHF).
Although they did not demonstrated changes in the number of circulating EPCs,
they showed that adhesive and proliferative properties of EPCs are enhanced
during rhEPO treatment. Also, the presence of rhEPO in cell culture increases
proliferation of EPCs in a dose-dependent manner[56]. These effects
suggested that EPO or its recombinant analogue can regulate the process of
vascular repair and neoangiogenesis by mobilizing EPCs. At the same time, it
has been shown that rhEPO stimulates the production of endothelin 1 (ET-1)[57]
and plasminogen activator inhibitor-1 (PAI-1)[58], both involved in
the increasing of vascular resistance, which is one of the factors contributing
to the development of hypertension in CKD patients. Moreover, rhEPO also
directly suppresses activity of endothelial nitric oxide synthase (eNOS), a
primary controller of smooth muscle tone[59]. It is very important
information, since the hematocrit value increased during rhEPO therapy is not
itself associated with an increased risk for hypertension as long as
endothelial NOS production and the level of nitric oxide (NO) are adequate.
So far, at
least eight genes has been shown to be up-regulated by rhEPO in endothelial
cells which included proteins implicated in the regulation of vascular
functions (thrombospondin-1 and myosin regulatory light chain), gene products
involved in gene transcription and/or translation (c-myc purine-binding
transcription factor PuF, tryptophanyl-tRNA synthetase and S19 ribosomal
protein), subunits of mitochondrial enzymes related to energy transfer (NADH
dehydrogenase subunit 6 and cytochrome C oxidase subunit 1) and regulators of
signal transduction (protein tyrosine phosphatase G1)[60].
EPO has also
an impact on vascular smooth muscle cells, as demonstrated for animal models.
It has been shown that rhEPO alone or in the company of norepinephrine,
angiotensin II and ET-1 raises the cytosolic concentration of calcium by
stimulating PKC and MAPK signaling pathways[61,62]. However, studies
in renal failure patients confirmed that rhEPO therapy enhances vascular
responsiveness to norepinephrine, which explains development of hypertension
during treatment[63]. Although there are no studies confirming the
presence of EPOR on human smooth muscle cells, its presence has been
demonstrated in human skeletal muscle cells[64]. Rundqvist et al[64]
have shown that both satellite cells and skeletal muscle fibers express the
receptor. Expression of EPOR in these cells increases after exercises
simultaneously with the expression of vascular endothelial growth factor (VEGF)
A, which would support the thesis that EPO could influence process of
angiogenesis[54,55,64]. Authors also suggested that another reason
for EPOR activation in skeletal muscle would be protection against apoptosis
induced by reversible ischemia.
As in the case
of smooth muscle cells, numerous articles described the effect of EPO/rhEPO on
cardiac myocytes using animal models. In vitro studies demonstrated
activation of multiple signaling pathways in rhEPO-induced cardioprotection,
including JAK1/2, STAT3 and STAT5A, PI-3K and their downstream kinases, AKT, PKC
and MAP[65,66]. Moreover, Shi et al[66] showed
that rhEPO mediates resistance to myocardial ischemia not only by PKC and MAP
kinases, but also by activation of two potassium (KATP) channels and the
calcium-activated potassium (KCa) channel. Studies of Parsa et al[67]
revealed that rhEPO treatment can protect the ischemic and infarcted heart by
inhibition of apoptosis of cardiac myocytes and augmented cardiac contractility
and relaxation, even when rhEPO was given at the time of myocardial infarction.
Westenbrink et al[68] demonstrated that rhEPO promotes VEGF
expression predominantly in cardiomyocytes through STAT3 pathway, which in turn
stimulates myocardial endothelial proliferation and incorporation of EPCs.
According to their results, the direct effects of rhEPO on endothelial
sprouting is VEGF independent. Cardioprotective effects of rhEPO have also been
demonstrated in experimental autoimmune myocarditis (EAM)[69]. The
expression of EPOR was up-regulated in the myocardium of EAM and rhEPO reduced
the level of pro-inflammatory cytokines (IL-6 and TNF-α) and apoptotic
cardiomyocytes. These studies show that rhEPO can reduce myocardial
inflammation and heart failure, at least in part, by modulating the
inflammatory cytokine profiles and protecting myocytes from apoptosis.
Anemia is a
risk factor for increased mortality in patients with congestive heart failure.
Tissue hypoxia worsens the natural history of CHF by causing systemic
vasodilatation and reduction of arterial and perfusion process, which leads to
reflex vasoconstriction and tachycardia through activation of sympathetic
nervous system and activation of renin-angiotensin system (RAS) leading to
sodium and water retention. The increased plasma volume contributes to
peripheral edema and increases cardiac load resulting in progressive heart
remodeling and left ventricular hypertrophy (LVH). In dialysis patients, anemia
is also associated with increased frequency of LVH, mainly due to activation of
RAS. In both groups of patients rhEPO treatment not only increases hemoglobin
level, but also enhances cardiac output, reduces sympathetic activation,
improves coronary circulation and induces LHV regression[70-73].
Silverberg et al[74] draws attention to the need for close
cooperation between nephrologists, cardiologists and internists in recognizing
and treating the anemia, which would allow prevent the deterioration of the
CHF, chronic kidney disease and the anemia itself. At the same time, one must
be aware of the other effects of the use of rhEPO, mainly an increased blood
viscosity as a result of increased red blood cell mass but also intensified
production of ET-1[57] and PAI-1[58] in endothelial cells
and raised calcium concentrations in vascular smooth muscle cells[61-63],
since all these mechanisms promote an increased risk of thrombotic events.
Erythropoietin
and its receptor as potential neuroprotectors
In 1997, the EPO has been detected in ventricular cerebrospinal fluid
(CSF) of patients with traumatic brain injuries[75]. These studies
also revealed that EPO does not cross the intact blood-brain barrier (BBB),
implying that it is produced in the brain itself, probably in an
oxygen-dependent manner. Springborg et al[76] not only have
confirmed these observations in patients with subarachnoid haemorrhage 5 years
later, but also established the EPO concentration in CSF which was about 1
mU/mL.
Both EPO and
EPOR has been identified in undifferentiated neuroepithelial cells in human
embryos; their expression pattern showed a specific distribution changing
during fetal development[77]. In adults, EPOR expression is found
mainly in neurons, astrocytes and microglia, while EPO is produced only by
astrocytes[78]. Furthermore, presence of pro-inflammatory cytokines
(IL-1, IL-6 and TNF-α) decreased expression of EPO and its receptor in
astrocytes[78]. In the same way pro-inflammatory cytokines suppress
renal EPO production and thereby erythropoiesis in patients with cancer or
chronic inflammatory diseases, which leads to development of pro-inflammatory
cytokine-mediated anemia[79]. It has also been shown that TNF-α
down-regulates EPOR expression in erythroid cell lines probably through
decreasing expression and binding activity of GATA1[80], which is
known to be one of the main transcription factors regulating the expression of
the EPOR gene in erythroid cells[81]. Pro-inflammatory cytokines
have been shown to be involved very early in the course of cerebral palsy (CP);
they may cause brain damage through promoting toxic substances, like free
radicals, increasing activity and aggregation of platelet and activating blood
coagulation, or destroying BBB[82-84]. It has been demonstrated that
the amount of EPO was decreased while IL-6 and TNF-α was simultaneously
increased in CP children[85]. According to Tao et al[85],
although CP children have BBB injury, the long-time secretion of EPO in CNS
mostly depends on brain tissue. Authors hypothesized that early in CP HIF-1
activated by inflammatory stimulation enhances the secretion of EPO in the
brain. However, deepening of hypoxia or increased severity of infection induces
the release of many pro-inflammatory cytokines which compete with EPO through
the JAK/STAT pathway and consequently abolish its neuroprotective effect[85].
As in the
kidneys, the expression of EPO mRNA and the production of EPO in the central
nervous system (CNS) are stimulated by hypoxia and ischemia[86,87].
According to Chin et al[88], the neuroprotective effect of
EPO and its receptor requires the induction of EPO production by hypoxia and an
increase in EPOR expression in neurons resulting in increased sensitivity to
EPO, which is in contrast to erythropoiesis, where erythroid progenitor cells
already exhibit high levels of EPOR and are directly responsive to EPO
stimulation in hypoxic conditions. Their studies have also shown that hypoxia
induces EPOR expression, which appears to be a consequence of increased EPOR
gene transcription from the upstream region and proximal promoter[88].
As in the case
of vascular smooth muscle cells or cardiac myocytes, knowledge of the potential
functions of EPO in the brain is based on animal models and the available data
on the action of the hormone on erythropoiesis progenitors. Several
direct-acting mechanisms, by which EPO may protect neurons, has been proposed,
including modulation of synaptic transmission, protection from oxidative
stress, apoptosis and inflammatory factors or stimulation of angiogenesis
(Figure 4). It is generally believed that EPO in nervous cells activates
exactly the same signaling pathways as in the erythroid progenitors. Various
experimental models have demonstrated that EPO regulates many neural cell
functions, including regulation of the flow of calcium, membrane depolarization
or neurotransmitter synthesis. Koshimura et al[89] showed
that rhEPO increases uptake and intracellular calcium concentration in a
dose-related manner, induces membrane depolarization, activates MAPK and
stimulates dopamine release from neurons. Although rhEPO had no effect on
maximal activity of NOS, the increase in the level of NO was also observed.
Since NO is reported to stimulate release of different neurotransmitters[90],
authors suggested that EPO stimulates dopamine release, partly, by increasing
NO production. Other studies have shown that rhEPO inhibits calcium-dependent
glutamate release from neurons and at the same time it increases
desensitization of glutamate receptors thereby protecting cells from ischemic
damage[91-93]. However, Yamasaki et al[93]
determined, by comparing the effects of rhEPO and brain-derived neurotrophic
factor (BDNF), that the rhEPO itself is not sufficient to promote cell
survival, although it is useful in protecting neurons from glutamate- or
NO-induced toxicity. On the other hand, studies of Chong et al[94]
showed that, although endogenous EPO is not sufficient to maintain neuron
survival during free radical injury, administration of rhEPO at the
concentration of 1 U/mL prevents neuronal cell death by activation of AKT with
subsequent phosphorylation of the Bcl-2 family pro-apoptotic member Bad.
Additionally, the presence of rhEPO in neuronal cell culture protects neurons
from DNA fragmentation and membrane phosphatidylserine (PS) exposure through
the modulation of cysteine protease activities. Authors also demonstrated that
rhEPO prevents the induction of apoptotic protease-activating factor-1 (Apaf-1)
and enhances the expression of
anti-apoptotic Bcl-xL[95]. Anti-apoptotic properties of
erythropoietin in nervous central system has also been demonstrated by Um et
al[96] who showed that rhEPO prevents apoptosis of
differentiated human neuroblastoma cells expressing small numbers of
high-affinity EPOR by activating the STAT5, AKT and MAPK signaling pathways.
As mentioned
above, pro-inflammatory cytokines decrease EPO and its receptor expression in
nervous tissue, specifically in astrocytes[78]. However, EPO itself
can also interfere with the inflammatory process by reducing the expression of
pro-inflammatory cytokines, such as IL-6 and TNF-α in neuronal injury. Villa et
al[97] have demonstrated that rhEPO markedly reduces the
recruitment of leukocytes and microglia to the nerve tissue deprived of oxygen
supply. The production of the TNF-α, IL-6 and monocyte chemoattractant protein
(MCP) was decreased by more that 50% after rhEPO administration. Similar
results were obtained in the experimental autoimmune encephalomyelitis (EAE);
rhEPO not only diminished inflammation by reducing the level of IL-6, and glial
activation and proliferation in the spinal cord, but also delayed the onset of
EAE[98].
Indirectly,
EPO may act in neuroprotective manner by stimulating angiogenesis which
increases the transport capability of oxygen-carrying blood, provides extra
oxygen to brain and counteracts the effect of ischemia on neurons[99].
This is related to the above mentioned presence of EPOR on endothelial cells.
Brain endothelial cells not only express receptor but also proliferate, migrate
and differentiate in the presence of rhEPO[99,100]. Sirén et al[87]
demonstrated that hypoxic brain damage is associated with vascular EPOR
expression accompanied by increased expression of EPO and its receptor in
astrocytes. Authors showed that administration of rhEPO dramatically reduces
the volume of infarction through the inhibition of apoptosis of cells in the
tissue directly adjacent to the site damaged by cerebral occlusion causing
hypoxic injury[101]. Other studies have shown that rhEPO antagonizes
VEGF-induced permeability of the BBB by restoring changes in the distribution
pattern of inter-endothelial junction proteins and decreases the levels of eNOS[102].
The
above-described effects of EPO on brain tissue suggest a potential use of rhEPO
as a neuroprotective agent in a variety of disorders of the central nervous
system, especially in chronic neurodegenerative disorders like Alzheimer
disease (AD), Parkinson’s disease (PD) or multiple sclerosis. Epidemiological
studies in USA have shown that AD is less common in states with higher
geographic altitude suggesting that individual level of EPO can be of
importance in the development of the disease[103]. Indeed, Assaraf et
al[104] showed that the expression of EPOR is significantly increased
in human AD and mild cognitive impairment temporal cortex compared to no
cognitive impairment brain tissue. The number of EPOR-positive astrocytes in
temporal and hippocampal regions was correlated with clinical,
neuropsychologic, and neuropathologic indices[104]. In the authors'
opinion, the high expression of the receptor in astrocytes is probably an
adaptive response to oxidative stress that reaches its maximum intensity in
preclinical and the very earliest stages of sporadic AD. In 2012, Zhi-Kun et
al[105] demonstrated that rhEPO can protect cells from apoptosis
induced by neurotoxic decapeptide Aβ 25–35 which was associated with the
activation of PI-3K-AKT signaling pathway. On the other hand, studies of Jang et
al[106] revealed that rhEPO administration for 12 months has
beneficial effects on non-motor symptoms in PD patients according to the NMS
Scale (NMSS) and the 39-Item Parkinson's Disease Questionnaire (PDQ-39). Since
oxidative stress, apoptosis, excitotoxicity, protein mishandling, inflammation
and microglial activation are part of the processes that eventually result in
neurodegeneration, it is possible that rhEPO could provide a useful therapeutic
strategy for these diseases.
Conlusions
The use of rhEPO significantly improved the health and quality of life
of ESRD patients. This is related not only to the improvement of parameters of
red blood cells, but probably also the potential impact of rhEPO on other cells
and tissues, especially monocytes, lymphocytes, endothelial cells and neurons.
Studies show that it has potentially beneficial influence on cellular processes
such as proliferation or angiogenesis. However, one must carefully draw
conclusions from the research results that can be found in the scientific
literature because not all of the observations have been confirmed in human
material. While the effects of EPO on the immune system in many cases have been
reported in human immune cells and have been conducted mainly in patients
treated with rhEPO, knowledge of hormone action on the central nervous or
cardiovascular system is based largely on animal models. In 2012, Elliott et
al[107] demonstrated that only erythroid cells have high levels
of EPOR mRNA and protein while in nonhematopoietic tissues (like brain or
heart) and other hematopoietic cell types its expression is undetectable. In
addition, they have failed to demonstrate the effect of rhEPO on angiogenesis
or survival of different cell types[107]. The authors drew attention
to the fact that the cytoprotective or angiogenic properties of rhEPO observed
in animal studies does not necessarily translate into the clinic. In fact, the
promising results from some experiments conducted in animal models of stroke
led to clinical trials that had failed in phase II/III because patients demonstrated
many different complications, including intercerebral hemorrhage, brain edema
or thrombotic events[108]. Also, a higher death rate was observed in
patients receiving EPO, particularly in those who were pretreated with
thrombolysis[108]. Similarly concerns apply to studies on the effect
of rhEPO/EPO in the immune system; significant differences between mouse and
human immunology have been described for years[109]. However, in
light of so many studies, the effect of EPO on cells other than erythroid
progenitors cannot be underestimated. But surely, the potential role of EPO
beyond erythropoiesis requires a well-planned experiments on human material.
Until then, rhEPO will be still indicated for treatment of anemia in patients
with chronic kidney disease.
CONFLICT OF INTERESTS
The authors have no conflicts of interest to declare.
REFERENCES
1. Schuster
SJ, Badiavas EV, Costa-Giomi P, Weinmann R, Erslev AJ, Caro J. Stimulation of
erythropoietin gene transcription during hypoxia and cobalt exposure. Blood 1998; 73: 13-16.
2. Lacombe
C, Mayeux P. Biology of erythropoietin. Haematologica 1998;
83: 724-732.
3. Wang
GL, Semenza GL. Characterization of hypoxia-inducible factor 1 and regulation
of DNA binding activity by hypoxia. J Biol Chem 1993; 268:
21513-21518.
4. Kallio
PJ, Pongratz I, Gradin K, McGuire J, Poellinger L. Activation of
hypoxia-inducible factor 1 alpha: posttranscriptional regulation and
conformational change by recruitment of the Arnt transcription factor. Proc Natl Acad Sci USA 1997; 94: 5667-5672.
5. Salceda
S, Caro J. Hypoxia-inducible factor 1 alpha (HIF-1 alpha) protein is rapidly
degraded by the ubiquitin-proteasome system under normoxic conditions. Its
stabilization by hypoxia depends on redox-induced changes. J
Biol Chem 1997; 272: 22642-22647.
6. Fisher
JW. Erythropoietin: physiologic and pharmacologic update. Exp Biol Med 2003; 228:1-14.
7. Witthuhn
BA, Quelle FW, Silvennoinen O, Yi T, Tang B, Miura O, Ihle JN. JAK2 associates
with the erythropoietin receptor and is tyrosine phosphorylated and activated
following stimulation with erythropoietin. Cell 1993; 74:
227-236.
8. Wakao
H, Harada N, Kitamura T, Mui AL, Miyajima A. Interleukin 2 and erythropoietin
activate STAT5/MGF via distinct pathways. EMBO J 1995; 14:
2527-2535.
9. Damen
JE, Mui ALF, Puil L, Pawson T, Krystal G. Phosphatidylinositol 3-kinase
associates, via its Src homolgy 2 domains, with the activated erythropoietin
receptor. Blood 1993; 81: 3204-3210.
10. Myklebust
JH, Smeland EB, Josefsen D, Sioud M. Protein kinase C-alpha isoform is involved
in erythropoietin-induced erythroid differentiation of CD34(+) progenitor cells
from human bone marrow. Blood 2000; 95: 510-518.
11. Sui
X, Krantz SB, You M, Zhao Z. Synergistic activation of MAP kinase (ERK1/2) by
erythropoietin and stem cell factor is essential for expanded erythropoiesis. Blood 1998; 92: 1142-1149.
12. Miyake
T, Kung CKH, Goldwasser E. Purification of human erythropoietin. J Biol Chem 1977; 252: 5558-5564.
13. Jacobs
K, Shoemaker C, Rudersdorf R, Neill SD, Kaufman RJ, Mufson A, Seehra J, Jones
SS, Hewick R, Fritsch EF. Isolation and characterization of genomic and cDNA
clones of human erythropoietin. Nature 1985; 313: 806-810.
14. Lin
FK, Suggs S, Lin CH, Browne JK, Smalling R, Egrie JC, Chen KK, Fox GM, Martin
F, Stabinsky Z, Badrawi SM, Lai PH, Goldwasser E. Cloning and expression of the
human erythropoietin gene. Proc Natl Acad Sci USA 1985; 82:
7580-7584.
15. Eschbach
JW, Egrie JC, Downing MR, Browne JK, Adamson JW. Correction
of the anemia of end-stage renal disease with recombinant human erythropoietin.
N Engl J Med 1987; 316: 73-78.
16. Eschbach
JW. Current concepts of anemia management in chronic renal failure: impact of
NKF-DOQI. Semin Nephrol 2000; 20: 320-329.
17. Sela
S, Shurtz-Swirski R, Sharon R, Manaster J, Chezar J, Shkolnik G, Shapiro G,
Shasha SM, Merchav S, Kristal B. The polymorphonuclear
leukocyte – a new target for erythropoietin. Nephron 2001; 88: 205-210.
18. Lisowska KA, Debska-Slizien A, Bryl E,
Rutkowski B, Witkowski JM. Erythropoietin receptor is expressed on
human peripheral blood T and B lymphocytes and monocytes and is modulated by
recombinant human erythropoietin treatment. Artif Organs 2010; 348: 654-662.
19. Anagnostou
A, Liu Z, Steiner M, Chin K, Lee ES, Kesseimian N, Noguchi CT. Erythropoietin
receptor mRNA expression in human endothelial cells. Proc
Natl Acad Sci USA 1994; 91: 3974-3978.
20. Anagnostou
A, Lee ES, Kessimian N, Levinson R, Steiner M. Erythropoietin has a mitogenic
and positive chemotactic effect on endothelial cells. Proc
Natl Acad Sci USA 1990; 87: 5978-5982.
21. Chin
K, Yu X, Beleslin-Cokic B, Liu C, Shen K, Mohrenweiser HW, Noguchi CT.
Production and processing of erythropoietin receptor transcripts in brain. Mol
Brain Res 2000; 81: 29-42.
22. Nagai
A, Nakagawa E, Choi HB, Hatori K, Kobayashi S, Kim SU. Erythropoietin
and erythropoietin receptors in human CNS neurons, astrocytes, microglia, and
oligodendrocytes grown in culture. J Neuropathol Exp Neurol 2001; 60:
386-392.
23. Farrell
F, Lee A. The erythropoietin receptor and its expression in
tumor cells and other tissues. The Oncologist 2004; 9: 18-30.
24. Berman
SJ. Infections in patients with end-stage renal disease.
An overview. Infect Dis Clin North Am 2001; 15:
709-720.
25. Rysz
J, Banach M, Cialkowska-Rysz A, Stolarek R, Barylski M, Drozdz J, Okonski P.
Blood serum levels of IL-2, IL-6, IL-8, TNF-alpha and IL-1beta in patients on
maintenance hemodialysis. Cell Mol Immunol 2006; 3: 151-154.
26. Lisowska
KA, Dębska-Ślizień A, Radzka M, Witkowski JM, Rutkowski B, Bryl E. Recombinant
human erythropoietin treatment of chronic renal failure patients normalizes
altered phenotype and proliferation of CD4-positive T lymphocytes. Artif Organs
2010; 34: e77-e84.
27. Lisowska
KA, Dębska-Ślizień A, Jasiulewicz A, Heleniak Z, Bryl E, Witkowski JM.
Hemodialysis affects phenotype and proliferation of CD4-positive T lymphocytes.
J Clin Immunol 2012; 1: 189-200.
28. Allegra
V, Vasile A, Maschio M, Mengozzi G. Immune response after vaccination with
recombinant hepatitis surface antigen in maintenance hemodialysis patients and
healthy controls. Nephron 1992; 61: 339-340.
29. Bryl
E, Myśliwska J, Dębska-Ślizień A, Trzonkowski P, Rachoń D, Bułło B, Zdrojewski
Z, Myśliwski A, Rutkowski B. Recombinant human erythropoietin stimulates
production of interleukin 2 by whole blood cell cultures of hemodialysis
patients. Artif Organs 1999; 23: 809-816.
30. Trzonkowski
P, Myśliwska J, Dębska-Ślizień A, Bryl E, Rachoń D, Myśliwski A, Rutkowski B.
Long-term therapy with recombinant human erythropoietin decreases percentage of
CD152(+) lymphocytes in primary glomerulonephritis haemodialysis patients. Nephrol
Dial Transplant 2002; 17: 1070-1080.
31. Bryl
E, Myśliwska J, Dębska-Ślizień A, Rachoń D, Bułło B, Lizakowski S, Myśliwski A,
Rutkowski B. The influence of recombinant human erythropoietin on tumor
necrosis factor α and interleukin 10 production by whole blood cell cultures of
hemodialysis patients. Artif Organs 1998; 22: 177-184.
32. William
J, Saad N, Salib M, Riad H, Mahran KS, Iskander I, Cozma G, Barsoum R. The acute effect of intravenously administered recombinant human
erythropoietin on the immune response of uremic patients maintained on regular
hemodialysis. Artif Organs 1998; 22: 192-196.
33. Kimata
H, Yoshida A, Ishioka C, Masuda S, Sasaki R, Mikawa H. Human recombinant
erythropoietin directly stimulates B cells immunoglobulin production and
proliferation in serum-free medium. Clin Exp Immunol 1991;
85: 151-156.
34. Ueki
Y, Nagata M, Miyake S, Tominaga Y. Lymphocyte subsets in hemodialysis patients
treated with recombinant human erythropoietin. J Clin Immunol
1993; 13: 279-287.
35. Kristal
B, Shurtz-Swirski R, Shasha SM, Manaster J, Shapiro G, Furmanov M, Hassan K,
Weissman I, Sela S. Interaction between erythropoietin and peripheral
polymorphonuclear leukocytes in hemodialysis patients. Nephron
1999; 81: 406-413.
36. Shurtz-Swirski
R, Kristal B, Shasha SM, Shapiro G, Geron R, Sela S. Interaction between
erythropoietin and peripheral polymorphonuclear leukocytes in continuous
ambulatory dialysis patients. Nephron 2002; 91: 759-761.
37. Kristal
B, Shurtz-Swirski R, Tanhilevski O, Shapiro G, Shkolnik G, Chezar J, Snitkovsky
T, Cohen-Mazor M, Sela S. Epoetin-alpha: preserving
kidney function via attenuation of polymorphonuclear leukocyte priming. Isr Med
Assoc J 2008; 10: 266-272.
38. Lee
S, Margolin K. Cytokines in cancer immunotherapy. Cancers 2011; 3: 3856-3893.
39. Wakao
H, Harada N, Kitamura T, Mui AL, Miyajima A. Interleukin 2 and erythropoietin
activate STAT5/MGF via distinct pathways. EMBO J 1995; 14:
2527-2535.
40. Pallard
C, Goulleux F, Charon M, Groner B, Gisselbrecht S, Dusanter-Fourt I.
Interleukin-3, erythropoietin and prolactin activate a STAT-5-like factor in
lymphoid cells. J Biol Chem 1995; 270: 15942-15945.
41. Lisowska
KA, Debska-Slizien A, Jasiulewicz A, Jóźwik A, Rutkowski B, Bryl E, Witkowski JM.
Flow cytometric analysis of STAT5 phosphorylation and CD95 expression in CD4+ T
lymphocytes treated with recombinant human erythropoietin. J Recept Signal
Transduct Res 2011; 31: 241-246.
42. Shinjo
K, Takeshita A, Higuchi M, Ohnishi K, Ohno R. Erythropoietin receptor
expression on human bone marrow erythroid precursor cells by a newly-devised
quantitative flow-cytometric assay. Br J Haematol 1997; 96:
551-558.
43. Spaan
M, Groothuismink ZM, Koning L, Roomer R, Janssen HL, De Knegt RJ, Boonstra A.
Erythropoietin administration suppresses human monocyte function in vitro
and during therapy-induced anemia in HCV patients. Antiviral Res 2013; 98:
469-475.
44. Cravedi
P, Manrique J, Hanlon KE, Reid-Adam J, Brody J, Prathuangsuk P, Mehrotra A,
Heeger PS. Immunosuppressive effects of erythropoietin on human alloreactive T
cells. J Am Soc Nephrol 2014; 25: 2003-2015.
45. Lisowska
KA, Frackowiak JE, Mikosik A, Witkowski JM: Changes in the expression of
transcription factors involved in modulating the expression of EPO-R in
activated human CD4-positive lymphocytes. PLoS One 2013; 8: e60326.
46. Lisowska
KA, Debska-Slizien A, Jasiulewicz A, Daca A, Bryl E, Witkowski JM. The influence of recombinant human erythropoietin on apoptosis and
cytokine production of CD4+ lymphocytes from hemodialyzed patients. J
Clin Immunol 2013; 33: 661-665.
47. Choukroun
G, Kamar N, Dussol B, Etienne I, Cassuto-Viguier E, Toupance O, Glowacki F,
Moulin B, Lebranchu Y, Touchard G, JaureguyM, Pallet N, Le Meur Y, Rostaing L,
Martinez F, CAPRIT Study Investigators. Correction of postkidney transplant
anemia reduces progression of allograft nephropathy. J Am SocNephrol 2012; 23:
360-368.
48. Cassis
P, Gallon L, Benigni A,MisterM, Pezzotta A, Solini S, Gagliardini E, Cugini D,
Abbate M, Aiello S, Rocchetta F, Scudeletti P, Perico N, Noris M, Remuzzi G.
Erythropoietin, but not the correction of anemia alone, protects from chronic
kidney allograft injury. Kidney Int 2012; 81: 903-918.
49. Shapiro
VS, Truitt K, Imboden JB, Weiss A. CD28 mediates transcriptional upregulation
of the interleukin-2 (IL-2) promoter
through a composite element containing the CD28RE and NF-IL-2B AP-1
sites. Mol Cell Biol 1997; 17: 4501-4508.
50. Bryl
E, Vallejo AN, Weyand CM, Goronzy JJ. Down-regulation of CD28
expression by TNF-alpha. J Immunol 2001; 167: 3231-3238.
51. Ascensao
JL, Vercellotti GM, Jacob HS, Zanjani ED. Role of endothelial cells in human
hematopoiesis: modulation of mixed colony growth in vitro. Blood 1984; 63: 553-558.
52. Graber
SE, Krantz SB. Erythropoietin: biology and clinical use. Hematol Oncol Clin
North Am 1989; 3: 369-400.
53. Sawyer ST, Krantz SB, Sawada K. Receptors
for erythropoietin in mouse and human erythroid cells and placenta. Blood 1989; 74: 103-109.
54. Bahlmann
FH, De Groot K, Spandau JM, Landry AL, Hertel B, Duckert T, Boehm SM, Menne J,
Haller H, Fliser D. Erythropoietin regulates endothelial progenitor cells.
Blood 2004; 103: 921-926.
55. Bahlmann
FH, DeGroot K, Duckert T, Niemczyk E, Bahlmann E, Boehm SM, Haller H, Fliser D.
Endothelial progenitor cell proliferation and differentiation is regulated by
erythropoietin. Kidney Int 2003; 64: 1648-1652.
56. George
J, Goldstein E, Abashidze A, Wexler D, Hamed S, Shmilovich H, Deutsch V, Miller
H, Keren G, Roth A. Erythropoietin promotes endothelial progenitor cell
proliferative and adhesive properties in a PI 3-kinase-dependent manner.
Cardiovasc Res 2005; 68: 299-306.
57. Carlini
RG, Gupta A, Liapis H, Rothstein M. Endothelin-1 release by erythropoietin
involves calcium signaling in endothelial cells. J Cardiovasc
Pharmacol 1995; 26: 889-892.
58. Nagai
T, Akizawa T, Kohjiro S, Koiwa F, Nabeshima K, Niikura K, Kino K, Kanamori N,
Kinugasa E, Ideura T. rHuEPO enhances the production of plasminogen activator
inhibitor-1 in cultured endothelial cells. Kidney Int 1996;
50: 102-107.
59. Wang XQ, Vaziri ND.
Erythropoietin depresses nitric oxide synthase expression by human endothelial
cells. Hypertension 1999; 33: 894-899.
60. Födinger
M, Fritsche-Polanz R, Buchmayer H, Skoupy S, Sengoelge G, Hörl WH, Sunder-Plassmann G. Erythropoietin-inducible immediate-early genes
in human vascular endothelial cells. J Investig Med 2000; 48: 137-149.
61. Akimoto
T, Kusano E, Fujita N, Okada K, Saito O, Ono S, Ando Y, Homma S, Saito T, Asano
Y. Erythropoietin modulates angiotensin II- or noradrenaline-induced Ca(2+)
mobilization in cultured rat vascular smooth-muscle cells. Nephrol Dial
Transplant 2001; 16: 491-499.
62. Kusano
E, Akimoto T, Umino T, Yanagiba S, Inoue M, Ito C, Ando Y, Asano Y. Modulation
of endothelin-1-induced cytosolic free calcium mobilization and
mitogen-activated protein kinase activation by erythropoietin in vascular
smooth muscle cells. Kidney Blood Press Res 2001; 24: 192-200.
63. Hand
MF, Haynes WG, Johnstone HA, Anderton JL, Webb DJ. Erythropoietin
enhances vascular responsiveness to norepinephrine in renal failure. Kidney Int 1995; 48: 806-813.
64. Rundqvist
H, Rullman E, Sundberg CJ, Fischer H, Eisleitner K, Ståhlberg M, Sundblad P,
Jansson E, Gustafsson T. Activation of the erythropoietin receptor in human
skeletal muscle. Eur J Endocrinol 2009; 161: 427-434.
65. Rafiee
P, Shi Y, Su J, Pritchard KA Jr, Tweddell JS, Baker JE. Erythropoietin protects
the infant heart against ischemia-reperfusion injury by triggering multiple
signaling pathways. Basic Res Cardiol 2005; 100: 187-197.
66. Shi
Y, Rafiee P, Su J, Pritchard KA Jr, Tweddell JS, Baker JE. Acute
cardioprotective effects of erythropoietin in infant rabbits are mediated by
activation of protein kinases and potassium channels. Basic Res Cardiol 2004;
99: 173-182.
67. Parsa CJ, Matsumoto A, Kim J, Riel RU,
Pascal LS, Walton GB, Thompson RB, Petrofski JA, Annex BH, Stamler JS, Koch WJ. A novel protective effect of erythropoietin in the infarcted heart.
J Clin Invest 2003; 112: 999-1007.
68. Westenbrink
BD, Ruifrok WP, Voors AA, Tilton RG, van Veldhuisen DJ, Schoemaker RG, van
Gilst WH, de Boer RA. Vascular endothelial growth factor is crucial for
erythropoietin-induced improvement of cardiac function in heart failure.
Cardiovasc Res 2010; 87: 30-39.
69. Mitsuma
W, Ito M, Kodama M, Fuse K, Okamura K, Minagawa S, Kato K, Hanawa H, Toba K,
Nakazawa M, Aizawa Y. Cardioprotective effects of recombinant human
erythropoietin in rats with experimental autoimmune myocarditis. Biochem
Biophys Res Commun 2006; 344: 987-994.
70. Goldberg
N, Lundin AP, Delano B, Friedman EA, Stein RA. Changes in left ventricular
size, wall thickness, and function in anemic patients treated with recombinant
human erythropoietin. Am Heart J 1992; 124: 424-427.
71. Linde
T, Wikström B, Andersson LG, Danielson BG. Renal anaemia treatment with
recombinant human erythropoietin increases cardiac output in patients with
ischaemic heart disease. Scand J Urol Nephrol 1996; 30:
115-120.
72. Löw-Friedrich
I, Grützmacher P, März W, Bergmann M, Schoeppe W. Long-term echocardiographic
examinations in chronic hemodialysis patients substituted with recombinant
human erythropoietin. Blood Purif 1990; 8: 272-278.
73. Silverberg
DS, Wexler D, Blum M, Keren G, Sheps D, Leibovitch E, Brosh D, Laniado S,
Schwartz D, Yachnin T, Shapira I, Gavish D, Baruch R, Koifman B, Kaplan C,
Steinbruch S, Iaina A. The use of subcutaneous erythropoietin and intravenous
iron for the treatment of the anemia of severe, resistant congestive heart
failure improves cardiac and renal function and functional cardiac class, and
markedly reduces hospitalizations. J Am Coll Cardiol 2000; 35: 1737-1744.
74. Silverberg
DS, Wexler D, Blum M, Schwartz D, Wollman Y, Iaina A. Erythropoietin should be
part of congestive heart failure management. Kidney Int Suppl 2003; 87:
S40-S47.
75. Marti
HH, Gassmann M, Wenger RH, Kvietikova I, Morganti-Kossmann MC, Kossmann T,
Trentz O, Bauer C. Detection of erythropoietin in human liquor: intrinsic
erythropoietin production in the brain. Kidney Int 1997; 51:
416-418.
76. Springborg
JB, Sonne B, Frederiksen HJ, Foldager N, Poulsgaard L, Klausen T, Jørgensen OS,
Olsen NV. Erythropoietin in the cerebrospinal fluid of patients with aneurysmal
subarachnoid haemorrhage originates from the brain. Brain Res 2003; 984:
143-148.
77. Juul
SE, Yachnis AT, Rojiani AM, Christensen RD. Immunohistochemical localization of
erythropoietin and its receptor in the developing
human brain. Pediatr Dev Pathol 1999; 2: 148-158.
78. Nagai
A, Nakagawa E, Choi HB, Hatori K, Kobayashi S, Kim SU. Erythropoietin
and erythropoietin receptors in human CNS neurons, astrocytes, microglia, and
oligodendrocytes grown in culture. J Neuropathol Exp Neurol 2001; 60:
386-392.
79. Morceau
F, Dicato M, Diederich M. Pro-inflammatory cytokine-mediated anemia: regarding
molecular mechanisms of erythropoiesis. Mediators Inflamm 2009; 2009: 405016.
80. Buck
I, Morceau F, Cristofanon S, Reuter S, Dicato M,
Diederich M. The inhibitory effect of the proinflammatory cytokine TNFalpha on
erythroid differentiation involves erythroid transcription factor modulation.
Int J Oncol 2009; 34: 853-860.
81. Chin
K, Oda N, Shen K, Noguchi CT. Regulation of transcription of the human
erythropoietin receptor gene by proteins binding to GATA-1 and Sp1 motifs. Nucleic Acids Res 1995; 23: 3041-3049.
82. Leviton
A, Dammann O. Coagulation, inflammation, and the risk of neonatal white matter
damage. Pediatr Res 2004; 55: 541-545.
83. Murthy
V, Kennea NL. Antenatal infection/inflammation and fetal
tissue injury. Best Pract Res Clin Obstet Gynaecol 2007; 21: 479-489.
84. Phares
TW, Kean RB, Mikheeva T, Hooper DC. Regional differences in
blood-brain barrier permeability changes and inflammation in the apathogenic
clearance of virus from the central nervous system. J Immunol 2006; 176:
7666-7675.
85. Tao
W, Wen F, Zhang H, Liu G. The signal transduction mediated by erythropoietin
and proinflammatory cytokines in the JAK/STAT pathway in the children with
cerebral palsy. Brain Dev 2009; 31: 200-207.
86. Sakanaka
M, Wen TC, Matsuda S, Masuda S, Morishita E, Nagao M, Sasaki R. In vivo
evidence that erythropoietin protects neurons from ischemic damage. Proc Natl Acad Sci USA 1998; 95: 4635-4640.
87. Sirén
AL, Knerlich F, Poser W, Gleiter CH, Brück W, Ehrenreich H. Erythropoietin and
erythropoietin receptor in human ischemic/hypoxic brain. Acta Neuropathol 2001;
101: 271-276.
88. Chin
K, Yu X, Beleslin-Cokic B, Liu C, Shen K, Mohrenweiser HW, Noguchi CT.
Production and processing of erythropoietin receptor transcripts in brain.
Brain Res Mol Brain Res 2000; 81: 29-42.
89. Koshimura
K, Murakami Y, Sohmiya M, Tanaka J, Kato Y. Effects of erythropoietin on
neuronal activity. J Neurochem 1999; 72: 2565-2572.
90. Zhu
X, Luo L. Effect of nitroprusside (nitric oxide) on endogenous dopamine release
from rat striatal slices. J Neurochem 1992; 59: 932-935.
91. Kawakami
M, Sekiguchi M, Sato K, Kozaki S, Takahashi M. Erythropoietin receptor-mediated
inhibition of exocytotic glutamate release confers neuroprotection during
chemical ischemia. J Biol Chem 2001; 276: 39469-39475.
92. Morishita
E, Masuda S, Nagao M, Yasuda Y, Sasaki R. Erythropoietin receptor is expressed
in rat hippocampal and cerebral cortical neurons, and erythropoietin prevents in
vitro glutamate-induced neuronal death. Neuroscience
1997; 76: 105-116.
93. Yamasaki
M, Mishima HK, Yamashita H, Kashiwagi K, Murata K, Minamoto A, Inaba T.
Neuroprotective effects of erythropoietin on glutamate and nitric oxide toxicity
in primary cultured retinal ganglion cells. Brain Res 2005; 1050: 15-26.
94. Chong
ZZ, Kang JQ, Maiese K. Erythropoietin fosters both intrinsic and extrinsic
neuronal protection through modulation of microglia, Akt1, Bad, and
caspase-mediated pathways. Br J Pharmacol 2003; 138: 1107-1118.
95. Chong
ZZ, Kang JQ, Maiese K. Apaf-1, Bcl-xL, cytochrome c, and caspase-9 form the
critical elements for cerebral vascular protection by erythropoietin. J Cereb
Blood Flow Metab 2003; 23: 320-330.
96. Um
M, Gross AW, Lodish HF. A "classical" homodimeric erythropoietin
receptor is essential for the antiapoptotic effects of erythropoietin on
differentiated neuroblastoma SH-SY5Y and pheochromocytoma PC-12 cells. Cell
Signal 2007; 19: 634-645.
97. Villa
P, Bigini P, Mennini T, Agnello D, Laragione T, Cagnotto A, Viviani B,
Marinovich M, Cerami A, Coleman TR, Brines M, Ghezzi P. Erythropoietin
selectively attenuates cytokine production and inflammation in cerebral
ischemia by targeting neuronal apoptosis. J Exp Med 2003; 198: 971-975.
98. Agnello
D, Bigini P, Villa P, Mennini T, Cerami A, Brines ML, Ghezzi P. Erythropoietin
exerts an anti-inflammatory effect on the CNS in a model of experimental
autoimmune encephalomyelitis. Brain Res 2002; 952: 128-134.
99. Marti
HH, Bernaudin M, Petit E, Bauer C. Neuroprotection and Angiogenesis: Dual Role
of Erythropoietin in Brain Ischemia. News Physiol Sci 2000; 15: 225-229.
100. Yamaji
R, Okada T, Moriya M, Naito M, Tsuruo T, Miyatake K, Nakano Y. Brain capillary
endothelial cells express two forms of erythropoietin receptor mRNA. Eur J Biochem 1996; 239: 494-500.
101. Sirén
AL, Fratelli M, Brines M, Goemans C, Casagrande S, Lewczuk P, Keenan S, Gleiter
C, Pasquali C, Capobianco A, Mennini T, Heumann R, Cerami A, Ehrenreich H,
Ghezzi P. Erythropoietin prevents neuronal apoptosis after cerebral ischemia
and metabolic stress. Proc Natl Acad Sci USA 2001; 98: 4044-4049.
102. Martínez-Estrada
OM, Rodríguez-Millán E, González-De Vicente E, Reina M, Vilaró S, Fabre M. Erythropoietin protects the in vitro
blood-brain barrier against VEGF-induced permeability. Eur J Neurosci 2003; 18:
2538-2544.
103. Ismailov
RM. Erythropoietin and epidemiology of Alzheimer disease. Alzheimer Dis Assoc
Disord 2013; 27: 204-206.
104. Assaraf
MI, Diaz Z, Liberman A, Miller WH Jr, Arvanitakis Z, Li Y, Bennett DA, Schipper
HM. Brain erythropoietin receptor expression in Alzheimer disease and mild
cognitive impairment. J Neuropathol Exp Neurol. 2007; 66:
389-398.
105. Zhi-Kun
S, Hong-Qi Y, Zhi-Quan W, Jing P, Zhen H, Sheng-Di C.
Erythropoietin prevents PC12 cells from beta-amyloid-induced apoptosis via PI3K⁄Akt
pathway. Transl Neurodegener 2012; 1: 7.
106. Jang
W, Park J, Shin KJ, Kim JS, Kim JS, Youn J, Cho JW, Oh E, Ahn JY, Oh KW, Kim
HT. Safety and efficacy of recombinant human erythropoietin treatment of
non-motor symptoms in Parkinson's disease. J Neurol Sci 2014; 337: 47-54.
107. Elliott
S, Sinclair AM. The effect of
erythropoietin on normal and neoplastic cells. Biologics 2012; 6:
163-189.
108. Ehrenreich
H, Weissenborn K, Prange H, Schneider D, Weimar C, Wartenberg K, Schellinger
PD, Bohn M, Becker H, Wegrzyn M, Jähnig P, Herrmann M, Knauth M, Bähr M, Heide
W, Wagner A, Schwab S, Reichmann H, Schwendemann G, Dengler R, Kastrup A,
Bartels C, and for the EPO Stroke Trial Group. Recombinant
Human Erythropoietin in the Treatment of Acute Ischemic Stroke. Stroke
2009; 40: e647-e656.
109. Mestas
J and Hughes C. Of Mice and Not Men: Differences between Mouse and Human
Immunology. J Immunol 2004; 172: 2731-2738.
Peer reviewers: Elena
Masselli, MD, Hematology and BMT Unit, Parma University Hospital, Parma, Italy;
Periklis Dousdampanis, MD, PhD, Consultant Nephrologist, Hemodialysis Unit,
Kyanos Stavros, Patras,Greece.
Refbacks
- There are currently no refbacks.