Localization of specific erythropoietin binding sites in defined areas of the mouse brain.

Abstract

The main physiological regulator of erythropoiesis is the hematopoietic growth factor erythropoietin (EPO), which is primarily produced in the kidney of adult mammals and is induced in response to hypoxia. Binding of EPO to the EPO receptor (EPO-R), a member of the cytokine receptor superfamily, controls the terminal maturation of red blood cells. So far, EPO has been reported to act mainly on erythroid precursor cells. However, we have detected mRNA encoding both EPO and EPO-R in mouse brain by reverse transcription-PCR. Exposure to 0.1% carbon monoxide, a procedure that causes functional anemia, resulted in a 20-fold increase of EPO mRNA in mouse brain as quantified by competitive reverse transcription-PCR, whereas the EPO-R mRNA level was not influenced by hypoxia. Binding studies on mouse brain sections revealed defined binding sites for radioiodinated EPO in distinct brain areas. The specificity of EPO binding was assessed by homologous competition with an excess of unlabeled EPO and by using two monoclonal antibodies against human EPO, one inhibitory and the other noninhibitory for binding of EPO to EPO-R. Major EPO binding sites were observed in the hippocampus, capsula interna, cortex, and midbrain areas. Functional expression of the EPO-R and hypoxic upregulation of EPO suggest a role of EPO in the brain.Erythropoietin (EPO) is a 30.4-kDa glycoprotein which represents the major regulator of erythropoiesis (reviewed in refs. 1-3). The main site of EPO production switches during development from the fetal liver to the adult kidney. Fibroblast-like type I interstitial cells have been identified as the EPO-producing cell population in the kidney (4, 5). In the liver, both a subset of hepatocytes and the nonparenchymal Ito cells, also known as fat-storing or perisinusoidal cells, have been reported to be the source of EPO production (6, 7). EPO gene expression is regulated in an oxygen-dependent manner: hypoxic exposure results in elevated EPO production in mammals and in the EPO-producing human hepatoma cell lines HepG2 and Hep3B (1-3). Binding of EPO to the EPO receptor (EPO-R), a member of the cytokine receptor superfamily (8), leads to enhanced red blood cell production by suppressing programmed cell death of erythroid progenitor cells (reviewed in ref. 9). So far, EPO has been shown to act mainly on erythroid cells. However, apart from its key function in erythropoiesis, EPO may also influence the functional behavior of nonerythroid cells: EPO might have mitogenic and chemotactic effects on endothelial cells (10) and fetal liver stromal cells (11), both cell types harboring the EPO-R (12, 11). Stimulation of differentiation and increased DNA synthesis in response to EPO has been observed in megakaryocytes in vitro (13,14), which is consistent with functional expression of EPO-R The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. on those ce...

Comparison of neuroprotective effects of erythropoietin (EPO) and carbamylerythropoietin (CEPO) against ischemia-like oxygen–glucose deprivation (OGD) and NMDA excitotoxicity in mouse hippocampal slice cultures

“…In the mature brain, expression of EPO appears to be upregulated by oxidative or nitrosative stress (Bernaudin et al, 1999(Bernaudin et al, , 2000Chong et al, 2003;Digicaylioglu et al, 1995). Within the brain, functional EPORs are expressed by different cell types such as neurons, glial cells and brain capillary endothelial cells (Genc et al, 2004a,b), while the main source of EPO within the CNS itself appears to be the astroglial cells (Bernaudin et al, 2000;Digicaylioglu et al, 1995;Juul et al, 1998;Marti et al, 1996;Masuda et al, 1993). Despite its extensive glycosylation and large size, EPO has been shown in multiple experimental species and in man to cross the blood brain barrier (BBB) when administered peripherally (Ehrenreich et al, 2004).…”

Erythropoietin and erythropoietin receptor expression in human prostate cancer

“…[9][10][11] In the brain where neurons express erythropoietin receptor and astrocytes express erythropoietin in a hypoxiainducible manner, erythropoietin was shown to protect against neuronal injury associated with ischemia. [12][13][14][15] In the uterus, erythropoietin-erythropoietin receptor function was shown to be involved in the regulation of cyclic uterine angiogenesis. 16 In another example of the diverse nonhematopoietic biological effects of erythropoietin-erythropoietin receptor, our recent studies have shown that erythropoietin is a cytokine that promotes angiogenesis and modulates the physiologic wound-healing cascade.…”

Erythropoietic neuroprotection: Holy Grail or potential to fail?

“…EPO and its receptor have been found in hematopoietic and several non-hematopoietic tissues including central nervous system, endothelium, cardiac myocytes, kidney, liver and some solid cancer cell lines [4]. Upon binding with EpoR an intricate series of intracellular signaling pathways are activated via Janus kinase 2 (Jak2) which increases the activity of intracellular mediators including signal transducer and activator of transcription 5 (STAT5), phosphoinositol 3 kinase (PI3K), mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK) and nuclear factor kappa B (NF-jB) [5][6][7]. These signaling pathways may promote neuronal survival by a number of putative mechanisms including: (1) neuroprotection, (2) neurogenesis, (3) antiinflammation, (4) angiogenesis and stabilization of neurovascular function, and (5) reduced oxidative stress.…”