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Endocrinology Vol. 148, No. 10 4711-4715
Copyright © 2007 by The Endocrine Society

Erythropoietin Inhibits Basal and Stimulated Corticotropin-Releasing Hormone Release from the Rat Hypothalamus via a Nontranscriptional Mechanism

Giuseppe Tringali, Giacomo Pozzoli, Lucia Lisi and Pierluigi Navarra

Institute of Pharmacology, Catholic University Medical School, 00168 Rome, Italy

Address all correspondence and requests for reprints to: Pierluigi Navarra, M.D., Institute of Pharmacology, Catholic University Medical School, Largo Francesco Vito 1, 00168 Rome, Italy. E-mail: pnavarra{at}rm.unicatt.it.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Brain hypoxia-ischemia induces a local increase in the levels of erythropoietin (EPO) and vascular endothelial growth factor (VEGF); this condition is also associated with acute activation of the hypothalamo-pituitary-adrenal (HPA) axis, suggesting that increased levels of EPO and VEGF in the hypothalamus may play a role in the control of HPA function. Thus, in this study we used rat hypothalamic explants to investigate whether EPO and VEGF can directly modulate CRH release; the latter was assessed by RIA measurement of the peptide in the incubation medium and hypothalamic tissue. EPO and VEGF effects were studied in short-term (1–3 h) experiments under basal conditions or after stimulation with 56 mM KCl or 10 µM veratridine. We observed that EPO (1–10 nM) significantly reduced CRH release and, in parallel, increased intrahypothalamic CRH content. VEGF tended to reduce CRH release without reaching statistical significance. Moreover, EPO, but not VEGF, inhibited KCl- and veratridine-stimulated CRH release and counteracted the parallel decrease in intrahypothalamic CRH induced by the two secretagogues. EPO effects were not mediated by modification of CRH gene expression, either in the absence or the presence of KCl or veratridine; in this paradigm, KCl and veratridine per se did not modify CRH gene expression. Our findings suggest that EPO contributes to the regulation of the HPA axis activation; in pathological conditions such as brain ischemia, this growth factor may control the HPA axis function, preventing possible detrimental effects of HPA overactivation.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
THE ERYTHROID GROWTH factor erythropoietin (EPO) displays various biological actions within the central nervous system (CNS) that are only in part related to its effect on erythropoiesis. EPO enters the rat brain via active uptake by astrocytes (1), being also synthesized within the CNS by neuronal and glial cells (2, 3, 4). These cells also express the EPO receptor both in human and rat brains. EPO was found to exert neuroprotective and neurotrophic actions in various animal models of brain injury; under ischemic conditions, protection by EPO was obviously related to counteraction of hypoxia (5, 6). Moreover, EPO exerts neuroprotective effects in different models of CNS inflammation (1, 7). In these conditions, neuroprotection has been attributed to antiinflammatory and/or antiapoptotic effects on neurons and glia, exerted by EPO independently from modulation of erythropoiesis (6, 7, 8, 9, 10). Pharmacological evidence strongly suggests that EPO neuroprotection is mediated by the activation of a receptor subtype devoid of erythropoietic activity (11).

Similar to EPO, vascular endothelial growth factor (VEGF) possesses neuroprotective and neurotrophic properties that are only partially related to its angiogenic activity because direct effects on neurons and glial cells have been clearly established (12). Native VEGF, a protein with 165 amino acid residues, exerts its mitogenic, angiogenic, and neurotrophic activities via the binding and activation of the VEGF receptor type 2 (13, 14). EPO, VEGF, and their receptors belong to different families of proteins that are not structurally related to each other; under certain conditions EPO even antagonizes the central effects of VEGF (15). However, the two growth factors share a common pattern of activation in the CNS, which is triggered by brain hypoxia and mediated by hypoxia-inducible transcription factors (16, 17).

Brain ischemia-hypoxia is also associated with activation of the stress responses and increased activity of the hypothalamo-pituitary-adrenal (HPA) axis either in humans (18, 19) or in experimental hypoxia of the rat (20); in both conditions, the activation of HPA is associated with increased neuronal vulnerability and poorer clinical outcome (21, 22, 23). The increases of EPO and VEGF occurring within the CNS as a consequence of ischemia-hypoxia might participate in the control of HPA axis function. However, no specific study has been performed thus far to investigate the possible relationships between brain EPO and VEGF, and the central control of HPA axis. In this study we have investigated the effects of EPO and VEGF on the gene expression, production, and release of CRH from rat hypothalamic explants, under basal conditions as well as after stimulation induced by Na+- and Ca2+-operated mechanisms.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Materials
A commercially available preparation of recombinant human EPO (Eprex; Janssen-Cilag SPA, Milan, Italy) was used. Recombinant human EPO is approximately 80% homologous to rodent EPO, and it has been biologically active in rodents for erythropoietic and other functions (1). EPO was diluted to working concentrations in incubation medium or 56 mM KCl medium. Native human VEGF and veratridine were purchased from Sigma Chemical Co. (St. Louis, MO). VEGF and veratridine were dissolved in 0.05 M PBS with 0.1% BSA or ethanol, respectively, and further diluted to working concentrations in incubation medium or 56 mM KCl medium when appropriated. All drugs tested did not interfere with the CRH assay.

Animals
Male Wistar rats (200–300 g) were used. They were kept four per cage and maintained at a temperature of 23 ± 1.5 C, with a relative humidity of 65 ± 2%. The animals were exposed to 12-h light (0600–1800 h) followed by 12-h dark, and had free access to food and water. The use of animals for this experimental work has been approved by the Italian Ministry of Health (licensed authorization to P.N.).

Hypothalamic incubation
Hypothalamic explants were performed as previously described (24). The hypothalami were then incubated in a 24-well plate (one hypothalamus per well), at 37 C in a humidified atmosphere consisting of 5% CO2 and 95% O2, in 300 µl MEM with Earle’s salts and stable glutamine (Biochrom AG, Berlin, Germany), supplemented with 0.2% BSA, 0,005% ascorbic acid, and 20 IU/ml aprotinin (pH 7.4). In these experimental conditions, hypothalamic tissues remained viable and functional, as assessed at the end of experiments by measurement of the lactic dehydrogenase activity taken as a marker of cytotoxicity (25). Thus, variations in CRH release did not appear to be related to nonspecific tissue damage.

After a 60-min preincubation period (during which the medium was changed every 20 min), the medium was replaced with fresh medium alone (control), or medium containing test substances at appropriate concentrations. At the end of the experiments, hypothalami were weighted and the incubation media collected and stored at –35 C until the measurement of CRH immunoreactivity. To measure intrahypothalamic CRH, the hypothalami were snap frozen and kept at –80 C, and then homogenized in 1 ml Tris-HCl 50 mM (pH 7.4), supplemented with 0.2% BSA and 40 IU/ml aprotinin, using a Teflon glass homogenizer (DuPont Co., Wilmington, DE). For RNA analysis, hypothalami were stored in 2 ml RNA Later TM solution (Ambion, Austin, TX) at –20 C until RNA extraction.

CRH RIA
CRH was measured by RIA as previously described (26). The detection limit of the assay was 1 pg/tube (100-µl sample volume for incubation media), with intraassay and interassay coefficients of variation of 5% and 10%, respectively. The amounts of both intrahypothalamic and released CRH were expressed as pg/mg wet tissue.

RNA extraction
Total RNA was extracted by the guanidine thiocyanate lysis method of Chomczynski and Sacchi (27). The average yield of RNA was 45–55 µg/hypothalamus.

RNase protection assay
CRH mRNA expression was measured by the RNase protection assay as previously described in detail (26).

Statistical analysis
All results are presented as the mean ± SEM of at least three different experiments performed in triplicate, unless otherwise specified. Data were analyzed by one-way ANOVA, and post hoc Dunnett or Newman-Keuls tests for comparison between group means, or else Student’s t test when appropriate, using Prism software (GraphPad, San Diego, CA). Differences were considered significant if P < 0.05.


   Results
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 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
In experiments looking at CRH release, data were expressed as pg of CRH/mg of wet hypothalamic tissue. Furthermore, total CRH content for each hypothalamus was calculated as the sum of the intrahypothalamic peptide and the released fraction; subsequently, the released and intrahypothalamic fractions were expressed as percentage of total CRH content. In 1-h experiments under basal conditions, EPO reduced CRH release from hypothalamic explants, with statistical significance reached at 1 nM, and, in parallel, increased CRH contents within the tissue (Fig. 1Go). Total CRH content (released + intrahypothalamic) did not vary in a significant manner among experimental groups.


Figure 1
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  		FIG. 1. EPO inhibits basal CRH secretion from hypothalamic explants. Left, EPO reduces in a concentration-dependent manner the percent fraction of CRH released in the incubation media compared with untreated controls. Right, EPO increases in a concentration-dependent manner the percent fraction of CRH localized in hypothalamic tissues. Data are expressed as the means ± SEM of 10 replicates per group (five hypothalami per group in two independent experiments). Total hypothalamic CRH contents were [data expressed as pg CRH/mg wet tissue; the mean ± SEM of (n) replicates per group]: controls 3.206 ± 0.315 (10 ), EPO 0.1 nM 2.988 ± 0.312 (10 ), EPO 1 nM 2.931 ± 0.455 (10 ), and EPO 10 nM 2.678 ± 0.563 (10 ). *, P < 0.05 vs. controls.

 
We did not observe any modification of CRH mRNA levels up to 3-h incubation in the presence of 10 nM EPO (Fig. 2Go), thus the reduction of CRH release induced by EPO was not related to down-regulation of CRH gene expression.


Figure 2
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  		FIG. 2. Effects of EPO on CRH mRNA levels in the rat hypothalamus. Hypothalamic explants were incubated for 1 or 3 h as indicated with medium alone [control (C)] or with medium containing 10 nM EPO and total RNA extracted. Results showed in the graph are from densitometric analysis of two independent experiments. A representative experiment is shown in the inset. rCRH, Rat CRH; rGAPDH, rat glyceraldehyde-3-phosphate dehydrogenase.

 
In experiments with KCl, hypothalami were treated with medium alone (control), 56 mM KCl alone, or 56 mM KCl in the presence of 1–10 nM EPO; whenever KCl was used, MEM was replaced by a solution consisting of 56 mM KCl and 67 mM NaCl, with the same concentration of the other ions as found in MEM. One-hour exposure to KCl significantly increased CRH release and, in parallel, significantly reduced CRH intrahypothalamic content (Fig. 3Go). In this paradigm, 1 and 10 nM EPO significantly inhibited the stimulatory action of KCl on CRH release, as well as KCl-induced reduction of intrahypothalamic peptide levels. Similar to basal experiments, total CRH content did not vary in a significant manner among experimental groups (Fig. 3Go). Another series of experiments was conducted using the Na+-channel opener veratridine as CRH secretagogue, and very similar results were obtained (Fig. 4Go). Consistent with the fact that 56 KCl and veratridine treatments did not increase the total amount of CRH per hypothalamus, we found that 1-h exposures to both secretagogues did not modify CRH mRNA levels (Fig. 5Go, left panel); such (lack of) effect was not modified at all by the addition of 10 nM EPO (Fig. 5Go, right panel).


Figure 3
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  		FIG. 3. EPO inhibits 56-mM stimulated CRH secretion from hypothalamic explants. Left, EPO reduces in a concentration-dependent manner the increase in the percent fraction of secreted CRH elicited by 56 mM KCl. Right, EPO counteracts in a concentration-dependent manner the depletion of intrahypothalamic CRH content elicited by 56 mM KCl. Data are the means ± SEM of 18 replicates per group (three hypothalami per group in six independent experiments). Total hypothalamic CRH contents were [data expressed as pg CRH/mg wet tissue; the mean ± SEM of (n) replicates per group]: controls 1.827 ± 0.175 (18 ); 56 mM KCl 2.097 ± 0.162 (18 ); 56 mM KCl + EPO 1 nM 1.925 ± 0.166 (18 ); and 56 mM KCl + EPO 10 nM 2.013 ± 0.200 (18 ). ***, P < 0.001 vs. controls. °°°, P < 0.001 vs. KCl alone.

 

Figure 4
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  		FIG. 4. EPO inhibits veratridine-stimulated CRH secretion from hypothalamic explants. Left, EPO reduces the increase in the percent fraction of secreted CRH elicited by 10 µM veratridine. Right, EPO counteracts the depletion of intrahypothalamic CRH content elicited by 10 µM veratridine. Data are the means ± SEM of 15 replicates per group (three hypothalami per group in five independent experiments). Total hypothalamic CRH contents were [data expressed as pg CRH/mg wet tissue; the mean ± SEM of (n) replicates per group]: controls 2.123 ± 0.280 (15 ); µM veratridine 2.039 ± 0.156 (15 ); 10 µM veratridine + EPO 1 nM 1.833 ± 0.160 (15 ); and µM veratridine + EPO 10 nM 1.849 ± 0.200 (15 ). ***, P < 0.001 vs. controls. °, P < 0.05 and °°, P < 0.01 vs. 10 µM veratridine.

 

Figure 5
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  		FIG. 5. Effect of 56 mM KCl or veratridine, alone or in the presence of EPO, on CRH mRNA levels in the rat hypothalamus. Hypothalamic explants were incubated for 1 h with vehicle, 56 mM KCl, or 10 µM veratridine, each given alone (left panel) or in combination with 10 nM EPO (right panel), and total RNA extracted. Results showed in the graph are from densitometric analysis of two independent experiments. A representative experiment is shown in the inset. rCRH, Rat CRH; rGAPDH, rat glyceraldehyde-3-phosphate dehydrogenase.

 
A series of experiments was performed using VEGF in the range of concentrations 5–100 ng/ml, under basal conditions or after stimulation by 56 mM KCl or veratridine, assessing both released and intrahypothalamic CRH levels. Similar to EPO, VEGF tended to reduce CRH secretion, but this effect did not attain statistical significance. Results are summarized in Table 1Go.


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  		TABLE 1. VEGF does not modify basal and stimulated CRH secretion from hypothalamic explants

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
In this study we found that EPO affects normal CRH secretion mechanisms, resulting in a concentration-dependent decrease of the released amounts of peptide and in a parallel accumulation within the hypothalamus. This phenomenon was observed either under basal condition or after stimulation by two CRH secretagogues, i.e. the sodium-channel opener veratridine and media containing high KCl concentrations (26). Both secretagogues, when given alone, increased significantly the fraction of peptide released in 1-h experiments, whereas reduced the intrahypothalamic levels; such shift occurred with no change in total CRH amounts, which is consistent with the observation that CRH mRNA levels were not modified during this time. Particularly in the 1- to 3-h time frame, all changes in CRH secretion induced by EPO, 56 mM KCl, and/or veratridine (given alone or in combination) were never associated with changes in CRH gene expression. VEGF tended to reduce the percentage of CRH released from the hypothalamus without a parallel increase in intrahypothalamic levels. The analysis of experimental results as adopted in the present study revealed that the net inhibitory effect of VEGF on CRH release did not reach statistical significance.

We have previously investigated the effects of various agents (drugs, endogenous factors, and related substances) on CRH release from the isolated hypothalamus, focusing on the fraction of the peptide released in the bath solution. In the present study, for the first time, we performed the simultaneous determination of the released and intrahypothalamic fractions in each hypothalamus, and expressed the results as percentage of total CRH content. This approach allows to distinguish between different conditions of reduced release, e.g. whether reduced release is accompanied by reduced tissue levels, which indirectly indicate decreased production, or conversely by increased levels, which point out possible interference with the secretion machinery. Thus, together with the assessment of CRH mRNA levels, this approach improved the evaluation of the effects of test substances on hypothalamic CRH turnover.

Evidence presented here indicates that EPO acutely inhibits CRH secretion from the hypothalamus through a nontranscriptional mechanism. This suggests that EPO might act via an interference with ion fluxes involved in the process of CRH secretion. In this regard, the pattern of inhibition upon the effects of the two secretagogues used in this study might provide some indication. In fact, veratridine elicits the release of neurotransmitters and neuropeptides stored in synaptic vesicles by increasing first Na+ ions influx, followed by an influx of Ca2+ ions, whereas high K+ concentrations act primarily by increasing Ca2+ ions inward currents (26); in this paradigm we have showed that factors affecting primarily Na+ currents, such as the antiepileptic drug lamotrigine, inhibit veratridine-, but not K+-, induced CRH release. Conversely, the present data would indicate that EPO acts by interfering with Ca2+ influx, i.e. the pathway shared by veratridine and 56 mM KCl. An effect of EPO on Ca2+ influx has been characterized in erythrocytes by Cheung (28), Chu (29), and Tong (30) et al.; these authors found that EPO elicits an increase in intracellular Ca2+, favoring ion flux through voltage-independent transient receptor potential channel 2 (TRPC2) Ca2+ channels. However, such evidence has been obtained in nonneural, nonexcitable cells and does not appear do be related to our experimental model, in which an increase in intracellular free Ca2+ would be rather associated with increased peptide secretion. Considering closer experimental paradigms, our findings are consistent with the data reported by Kawakami et al. (31), who showed that EPO reduces Ca2+-induced glutamate release from cultured cerebellar and hippocampal neurons; evidence from this group and others (3) suggests that neuroprotection afforded by EPO in vivo may be at least in part associated with a reduction of Ca2+-mediated excitotoxicity.

Here we showed that EPO treatments reduce both baseline and stimulated secretion of CRH from the isolated hypothalamus. The possible correlation between the present finding and the in vivo paradigm remains to be clarified; most of the studies on the relationships between EPO treatments and the regulation of HPA axis have been performed in patients receiving long-term EPO therapies because of kidney disease, a condition scarcely related to the acute in vitro rat paradigm. Kokot et al. (32) found that long-term treatments with EPO reduce ACTH and cortisol circulating levels in hemodialyzed patients, both under resting conditions and after hypoglycemic stimulus. Interestingly, these authors observed that the endocrine effects of exogenous EPO were not associated with changes in hemoglobin and hematocrit levels, suggesting that the effects of EPO were not, or they were only in part, a consequence of anemia improvement. Diez et al. (33) found a delayed peak of insulin-induced hypercortisolemia in hemodialysis patients receiving EPO compared with untreated controls, but there were no differences between the areas under the curve of total cortisol secreted during 120 min. Thus, notwithstanding huge differences between the experimental paradigms, it would appear that EPO treatments induce a blunted reactivity of the HPA axis in the clinical setting as well.

Concerning brain ischemia-hypoxia, EPO treatments afforded neuroprotection in ischemia after middle cerebral artery occlusion in the rat (6, 10), an effect mediated at least in part through an antiinflammatory action (10); it should be pointed out that the antiinflammatory properties of EPO bear no resemblance to the action mechanism of classical antiinflammatory agents because EPO has no effect on the production and release of proinflammatory cytokines and other mediators of inflammation from immune-inflammatory cells in vitro (8, 10). Indeed, the antiinflammatory action observed in vivo has been explained in terms of a secondary effect after the decrease in neuronal apoptosis (10). In this framework the putative inhibition of HPA axis by EPO has no direct relationship with so-called EPO antiinflammatory effects: the reduced glucocorticoid output would rather exacerbate any inflammatory phenomena.

On the other hand, it is well established that the activation of HPA axis occurring under hypoxic-ischemic conditions is associated with an increase in hypoxic neuronal injury, and higher cortisol levels are associated with poorer outcome and increased mortality in humans (18, 19, 20, 21, 22, 23). Thus, the putative ability of EPO to oppose HPA overactivation should be thought of as an additional mechanism accounting for EPO protection against neuronal damage during experimental brain hypoxia-ischemia, thereby reinforcing the rationale for trying the clinical efficacy of EPO, or its nonerythropoietic derivatives (11), in stroke and related diseases.


   Footnotes
 
This work was supported by Fondi di Ateneo 2006 (to G.T.).

Disclosure Information: The authors have nothing to declare.

First Published Online July 5, 2007

Abbreviations: CNS, Central nervous system; EPO, erythropoietin; HPA, hypothalamo-pituitary-adrenal; VEGF, vascular endothelial growth factor.

Received April 3, 2007.

Accepted for publication June 21, 2007.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Brines ML, Ghezzi P, Keenan S, Agnello D, de Lanerolle NC, Cerami C, Itri LM, Cerami A 2000 Erythropoietin crosses the blood-brain barrier to protect against experimental brain injury. Proc Natl Acad Sci USA 97:10526–10531[Abstract/Free Full Text]
  2. Masuda S, Okano M, Yamagishi K, Nagao M, Ueda M, Sasaki R 1994 A novel site of erythropoietin production. Oxygen-dependent production in cultured rat astrocytes. J Biol Chem 269:19488–19493[Abstract/Free Full Text]
  3. Morishita E, Masuda S, Nagao M, Yasuda Y, Sasaki R 1997 Erythropoietin receptor is expressed in rat hippocampal and cerebral cortical neurons, and erythropoietin prevents in vitro glutamate-induced neuronal death. Neuroscience 76:105–116[Medline]
  4. Nagai A, Nakagawa E, Choi HB, Hatori K, Kobayashi S, Kim SU 2001 Erythropoietin and erythropoietin receptors in human CNS neurons, astrocytes, microglia, and oligodendrocytes grown in culture. J Neuropathol Exp Neurol 60:386–392[Medline]
  5. Sakanaka M, Wen TC, Matsuda S, Masuda S, Morishita E, Nagao M, Sasaki R 1998 In vivo evidence that erythropoietin protects neurons from ischemic damage. Proc Natl Acad Sci USA 95:4635–4640[Abstract/Free Full Text]
  6. Siren 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 2001 Erythropoietin prevents neuronal apoptosis after cerebral ischemia and metabolic stress. Proc Natl Acad Sci USA 98:4044–4049[Abstract/Free Full Text]
  7. Agnello D, Bigini P, Villa P, Mennini T, Cerami A, Brines ML, Ghezzi P 2002 Erythropoietin exerts an anti-inflammatory effect on the CNS in a model of experimental autoimmune encephalomyelitis. Brain Res 952:128–134[CrossRef][Medline]
  8. Vairano M, Dello Russo C, Pozzoli G, Battaglia A, Scambia G, Tringali G, Aloe-Spiriti MA, Preziosi P, Navarra P 2002 Erythropoietin exerts anti-apoptotic effects on rat microglial cells in vitro. Eur J Neurosci 16:584–592[CrossRef][Medline]
  9. Digicaylioglu M, Lipton SA 2001 Erythropoietin-mediated neuroprotection involves cross-talk between Jak2 and NF-{kappa}B signalling cascades. Nature 412:641–647[CrossRef][Medline]
  10. Villa P, Bigini P, Mennini T, Agnello D, Laragione T, Cagnotto A, Viviani B, Marinovich M, Cerami A, Coleman TR, Brines M, Ghezzi P 2003 Erythropoietin selectively attenuates cytokine production and inflammation in cerebral ischemia by targeting neuronal apoptosis. J Exp Med 198:971–975[Abstract/Free Full Text]
  11. Leist M, Ghezzi P, Grasso G, Bianchi R, Villa P, Fratelli M, Savino C, Bianchi M, Nielsen J, Gerwien J, Kallunki P, Larsen AK, Helboe L, Christensen S, Pedersen LO, Nielsen M, Torup L, Sager T, Sfacteria A, Erbayraktar S, Erbayraktar Z, Gokmen N, Yilmaz O, Cerami-Hand C, Xie QW, Coleman T, Cerami A, Brines M 2004 Derivatives of erythropoietin that are tissue protective but not erythropoietic. Science 305:239–242[Abstract/Free Full Text]
  12. Greenberg DA, Jin K 2005 From angiogenesis to neuropathology. Nature 438:954–959[CrossRef][Medline]
  13. Ferrara N, Davis-Smith T 1997 The biology of vascular endothelial growth factor. Endocr Rev 18:4–25[Abstract/Free Full Text]
  14. Ferrara N, Gerber H-P, LeCouter J 2003 The biology of VEGF and its receptors. Nat Med 9:669–676[CrossRef][Medline]
  15. Martinez-Estrada OM, Rodriguez-Millan E, Gonzalez-De Vicente E, Reina M, Vilaro S, Fabre M 2003 Erythropoietin protects the in vitro blood-brain barrier against VEGF-induced permeability. Eur J Neurosci 18:2538–2544[CrossRef][Medline]
  16. Bernaudin M, Tang Y, Reilly M, Petit E, Sharp FR 2002 Brain genomic response following hypoxia and re-oxygenation in the neonatal rat. Identification of genes that might contribute to hypoxia-induced ischemic tolerance. J Biol Chem 277:39728–39738[Abstract/Free Full Text]
  17. Marti HH 2004 Erythropoietin and the hypoxic brain. J Exp Biol 207:3233–3242[Abstract/Free Full Text]
  18. Fassbender K, Schmidt R, Mossner R, Daffertshofer M, Hennerici M 1994 Pattern of activation of the hypothalamic-pituitary-adrenal axis in acute stroke. Relation to acute confusional state, extent of brain damage, and clinical outcome. Stroke 25:1105–1108[Abstract]
  19. Johansson A, Olsson T, Carlberg B, Karlsson K, Fagerlund M 1997 Hypercortisolism after stroke-partly cytokine-mediated? J Neurol Sci 147:43–47[CrossRef][Medline]
  20. Chen XQ, Du JZ, Wang YS 2004 Regulation of hypoxia-induced release of corticotropin-releasing factor in the rat hypothalamus by norepinephrine. Regul Pept 119:221–228[CrossRef][Medline]
  21. Strijbos PJ, Relton JK, Rothwell NJ 1994 Corticotrophin-releasing factor antagonist inhibits neuronal damage induced by focal cerebral ischaemia or activation of NMDA receptors in the rat brain. Brain Res 656:405–408[CrossRef][Medline]
  22. Krugers HJ, Knollema S, Kemper RH, Ter Horst GJ, Korf J 1995 Down-regulation of the hypothalamo-pituitary-adrenal axis reduces brain damage and number of seizures following hypoxia/ischaemia in rats. Brain Res 690:41–47[CrossRef][Medline]
  23. Marklund N, Peltonen M, Nilsson TK, Olsson T 2004 Low and high circulating cortisol levels predict mortality and cognitive dysfunction early after stroke. J Intern Med 256:15–21[CrossRef][Medline]
  24. Navarra P, Tsagarakis S, Faria MS, Rees LH, Besser GM, Grossman AB 1991 Interleukins-1 and -6 stimulate the release of corticotropin-releasing hormone-41 from rat hypothalamus in vitro via the eicosanoid cyclooxygenase pathway. Endocrinology 128:37–44[Abstract]
  25. Pozzoli G, Tringali G, Dello Russo C, Vairano M, Preziosi P, Navarra P 2001 HIV-1 Gp120 protein modulates corticotropin releasing factor synthesis and release via the stimulation of its mRNA from the rat hypothalamus in vitro: involvement of inducible nitric oxide synthase. J Neuroimmunol 118:268–276[CrossRef][Medline]
  26. Tringali G, Aubry JM, Navarra P, Pozzoli G 2006 Lamotrigine inhibits basal and Na+-stimulated, but not Ca2+-stimulated, release of corticotropin-releasing hormone from the rat hypothalamus. Psychopharmacology (Berl) 188:386–392[CrossRef][Medline]
  27. Chomczynski P, Sacchi N 1987 Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal Biochem 162:156–159[Medline]
  28. Cheung JY, Zhang XQ, Bokvist K, Tillotson DL, Miller BA 1997 Modulation of calcium channels in human erythroblasts by erythropoietin. Blood 89:92–100[Abstract/Free Full Text]
  29. Chu X, Cheung JY, Barber DL, Birnbaumer L, Rothblum LI, Conrad K, Abrasonis V, Chan YM, Stahl R, Carey DJ, Miller BA 2002 Erythropoietin modulates calcium influx through TRPC2. J Biol Chem 277:34375–34382[Abstract/Free Full Text]
  30. Tong Q, Chu X, Cheung JY, Conrad K, Stahl R, Barber DL, Mignery G, Miller BA 2004 Erythropoietin-modulated calcium influx through TRPC2 is mediated by phospholipase C{gamma} and IP3R. Am J Physiol Cell Physiol 287:C1667–C1678
  31. Kawakami M, Sekiguchi M, Sato K, Kozaki S, Takahashi M 2001 Erythropoietin receptor-mediated inhibition of exocytotic glutamate release confers neuroprotection during chemical ischemia. J Biol Chem 276:39469–39475[Abstract/Free Full Text]
  32. Kokot F, Wiecek A, Grzeszczak W, Klin M 1990 Influence of erythropoietin treatment on function of the pituitary-adrenal axis and somatotropin secretion in hemodialyzed patients. Clin Nephrol 33:241–246[Medline]
  33. Diez JJ, Iglesias P, Sastre J, Gomez-Pan A, Selgas R, Romero JR, Mendez J 1993 Influence of recombinant human erythropoietin treatment on cortisol responses to insulin-induced hypoglycemia in CAPD patients. Adv Perit Dial 9:336–341[Medline]




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Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals