Erythropoietin Gene Expression Research Articles

Nuclear Receptor Rev-erbα Role in Fine-Tuning Erythropoietin Gene Expression

The regulation of RBC homeostasis by erythropoietin (EPO) is critical for O2 transport and maintaining the adequate number of RBCs in vertebrates. Therefore, dysregulation in EPO synthesis results in disease conditions like polycythemia in the case of excessive EPO production and anemia, which occurs when EPO is inadequately produced. EPO plays a crucial role in treating anemic patients; however, its overproduction can increase blood viscosity, potentially leading to fatal heart failure. Consequently, the identification of druggable transcription factors (TFs) and their associated ligands capable of regulating EPO offers a promising therapeutic approach to address EPO-related disorders. This study unveils a novel regulatory mechanism involving two pivotal nuclear receptors (NRs), Rev-erbα and RORα, in the control of EPO gene expression. Rev-erbα acts as a cell-intrinsic negative regulator, playing a vital role in maintaining erythropoiesis at the correct level. It accomplishes this by directly binding to newly identified response elements within the human and mouse EPO gene promoter, thereby repressing EPO production. These findings are further supported by the discovery that a Rev-erbα agonist (SR9011) effectively suppresses hypoxia-induced EPO expression in mice. In contrast, RORα functions as a positive regulator of EPO gene expression, also binding to the same response elements in the promoter to induce EPO production. Finally, the results of this study revealed that the two NRs, Rev-erbα, and RORα, influence EPO synthesis in a negative and positive manner, suggesting that the modulating activity of these two NRs could provide a method to target disorders linked with EPO dysregulation.

Oxomer- and Reporter Gene-Based Analysis of FIH Activity in Cells.

Cellular and tissue adaptations to oxygen deprivation (hypoxia) are necessary for both normal physiology and disease. Responses to hypoxia are initiated by the cellular oxygen sensors prolyl-4-hydroxylase domain (PHD) proteins 1-3 and factor inhibiting HIF (FIH). These enzymes regulate the transcription factor hypoxia-inducible factor (HIF) in a hypoxia-sensitive manner. FIH also regulates proteins outside the HIF pathway, including the deubiquitinase OTUB1. Numerous preclinical analyses have demonstrated thattreatment with HIF hydroxylase inhibitors is beneficial and protective in many hypoxia-associated diseases. However, clinically available HIF hydroxylase inhibitors increase erythropoietin (EPO) gene expression and red blood cell production, which can be detrimental in hypoxia-associated conditions, such as ischemia/reperfusion injury of the heart or chronic inflammation. Our understanding of the relevance of FIH in (patho)physiology is only in its infancy, but FIH activity does not govern erythropoietin expression. Therefore, it is of prime interest to assess the relevance of FIH activity in (patho)physiology in detail, as it may contribute to developing novel therapeutic options for treating hypoxia-associated diseases that do not affect Epo regulation. Here, we describe specific protocols for two different methods to assess FIH enzymatic activity within cells, using a HIF-dependent firefly luciferase-reporter gene and an oxomer-dependent assay. Oxomers are oxygen-dependent stable protein oligomers formed by FIH, for example, with the deubiquitinase OTUB1. Oxomer formation directly depends on FIH activity, providing a suitable cellular readout for an easy-to-use analysis of FIH enzymatic activity in cellulo. These techniques permit an analysis of FIH activity toward HIF and outside the HIF pathway, allowing the investigation of FIH activity under different (patho)physiological conditions and assessment of novel (putative) inhibitors.

Quercetin’in HepG2 hücrelerinde, TNF-Alfa ve LPS ile indüklenen enflamasyonda, eritropoietin, HIF-1α, HIF-2α ve piroptoz ile ilgili genlerin ekspresyon seviyeleri üzerine etkileri

Purpose: TNF-α, which increases in the circulation as a result of systemic inflammation, suppresses the production of the erythropoiesis regulating hormone, erythropoietin (EPO) and causes inflammation anemia. The anti-inflammatory activity of quercetin has been reported in different studies. However, no study has been found showing the effect of this situation on EPO gene expression. For this purpose, we evaluated the effects of quercetin on inflammation and, more importantly, its effects on EPO, suppressed in the inflammatory environment and Hypoxia-inducible factors (HIF), which are stimulators of EPO synthesis. In addition, we aimed to evaluate the effect of quercetin on pyroptosis, which is defined as pro-inflammatory programmed cell death.
 Materials and Methods: We created inflammation models with TNF-α or LPS using HepG2 cells in vitro. In these inflammation models, we evaluated the effects of quercetin on proinflammatory mediators TNF-α, IL-1α, NF-κB gene expressions, EPO, HIF-1α, HIF-2α gene expressions, as well as pyroptosis-related caspase 1 and IL-18 gene expressions. 
 Results: Quercetin showed inflammatory effects by increasing TNF-α, IL-1α, and NF-κB mRNA levels. Consistent with this inflammatory effect, EPO mRNA expression was suppressed. HIF-1α and HIF-2α mRNA levels were increased. 
 Conclusion: These results suggested that the increase in HIFs could not prevent the suppressive effect of inflammatory cytokines and NF-κB on EPO production. However, it has been observed that it tends to suppress proinflammatory cell death by decreasing caspase 1 and IL-18 mRNA levels. These results show that quercetin may show conflicting effects, and further studies are needed to test its safety.

Roxadustat and its failure: A comparative dynamic study

Roxadustat, a small-molecule inhibitor of hypoxia-inducible factor prolyl hydroxylase domain 2 (HIF-PHD2) has been recently overruled by the American Food and Drug Administration (FDA) in Phase 3 clinical trials. This study provides insights into the dynamics of Roxadustat with PHD2 and proposes two FDA-approved drugs; Pemetrexed and Valrubicin to treat chronic kidney disease (CKD). Role of chemical scaffolds such as synthetic pyrimidine-based antifolate is found critical for PHD2 inhibitory activity, which is concurrent with the experimental findings for stimulating Endogenous erythropoietin (EPO) gene expression. Furthermore, Fe+2 and Mn+2 in solution are essential for imparting structural stability to the screened carboxylic and non-carboxylic acid drugs. Comparative analysis of FDA-approved drugs namely, Roxadustat, two-hit carboxylic, and non-carboxylic-acid type compounds (Pemetrexed and Valrubicin), as well as the control ligands (KU1 and 4JR), unveil structural dynamics of Roxadustat and its failure. However, the proposed FDA compounds, Pemetrexed and Valrubicin, used to treat mesothelioma, non-small cell lung cancer, and bladder cancer should be subjected to in vitro analysis for renal anemia.

Sildenafil Citrate Enhances Renal Organogenesis Following Metanephroi Allotransplantation into Non-Immunosuppressed Hosts.

In order to harness the potential of metanephroi allotransplantation to the generation of a functional kidney graft on demand, we must achieve further growth post-transplantation. Sildenafil citrate (SC) is widely known as a useful inductor of angiogenesis, offering renoprotective properties due to its anti-inflammatory, antifibrotic, and antiapoptotic effects. Here, we performed a laparoscopic metanephroi allotransplantation after embedding sildenafil citrate into the retroperitoneal fat of non-immunosuppressed adult rabbit hosts. Histology and histomorphometry were used to examine the morphofunctional changes in new kidneys 21 days post-transplantation. Immunofluorescence of E-cadherin and renin and erythropoietin gene expression were used to assess the tubule integrity and endocrine functionality. After the metanephroi were embedded in a 10 µM SC solution, the new kidneys’ weights become increased significantly. The E-cadherin expression together with the renin and erythropoietin gene expression revealed its functionality, while histological mature glomeruli and hydronephrosis proved the new kidneys’ excretory function. Thus, we have described a procedure through the use of SC that improves the outcomes after a metanephroi transplantation. This study gives hope to a pathway that could offer a handsome opportunity to overcome the kidney shortage.

Effects of sub-acute exposure to Sudan IV-adulterated palm oil on hematology-related parameters in male albino rats

ABSTRACT Palm oil (PO), the most consumed edible oil, is persistently adulterated with Sudan IV dye (S4D). We investigated the potential hematological derangements occasioned by ingesting S4D-adulterated PO. Thirty male albino rats were grouped into five (n = 6); Control, PO (10%), PO + S4D (100 mg), PO + S4D (250 mg), and S4D (250 mg). Rats received unadulterated or S4D-adulterated PO through diet for 21 days. Exposure to S4D (alone and via adulterated PO) provoked significant (p < 0.05) reductions in the packed cell volume, hemoglobin, red and white blood cell counts, neutrophils, lymphocytes, and eosinophils, while monocyte population was significantly (p < 0.05) elevated. The erythropoietin gene expression was downregulated, while monocyte chemoattractant protein-1 was upregulated in the kidneys of S4D-exposed groups compared to control and PO-alone groups. Notably, these hematological parameters were not significantly different (p > 0.05) in the unadulterated PO-exposed rats compared to the control. These results reveal the potential hematotoxic and immunotoxic effects of adulterating PO with S4D.

Esterification promotes the intracellular accumulation of roxadustat, an activator of hypoxia-inducible factors, to extend its effective duration

Kidney injury often causes anemia due to a lack of production of the erythroid growth factor erythropoietin (EPO) in the kidneys. Roxadustat is one of the first oral medicines inducing EPO production in patients with renal anemia by activating hypoxia-inducible factors (HIFs), which are activators of EPO gene expression. In this study, to develop prodrugs of roxadustat with improved permeability through cell membrane, we investigated the effects of 8 types of esterification on the pharmacokinetics and bioactivity of roxadustat using Hep3B hepatoma cells that HIF-dependently produce EPO. Mass spectrometry of cells incubated with the esterified roxadustat derivatives revealed that the designed compounds were deesterified after being taken up by cells and showed low cytotoxicity compared to the original compound. Esterification prolonged the effective duration of roxadustat with respect to EPO gene induction and HIF activation in cells transiently exposed to the compounds. In the kidneys and livers of mice, both of which are unique sites of EPO production, a majority of the methyl-esterified roxadustat was deesterified within 6 h after drug administration. The deesterified roxadustat derivative was continuously detectable in plasma and urine for at least 48 h after administration, while the administered compound became undetectable 24 h after administration. Additionally, we confirmed that methyl-esterified roxadustat activated erythropoiesis in mice by inducing Epo mRNA expression exclusively in renal interstitial cells, which have intrinsic EPO-producing potential. These data suggest that esterification could lead to the development of roxadustat prodrugs with improvements in cell membrane permeability, effective duration and cytotoxicity.

Hypothyroidism and its effect on serum vitamin D and iron among adult female: A review from Middle East perspective

Hypothyroidism is a pathophysiological phase in which insufficient hormones are produced, leading to an imbalance in basal metabolic rate and inefficiency in the physiological role of body systems. Vitamin D affects thyrocytes by decreasing thyroid-stimulating hormone (TSH) stimulated iodide uptake and cellular development. In hypothyroidism, hypovitaminosis D is due to malabsorption from the intestine and inactivation of vitamin D. Thyroid hormones induce erythropoietin gene expression causing an increase in the secretion of erythropoietin. Iron deficiency decreases the activity of the thyroid peroxidase enzyme. Hypothyroidism can cause microcytic anaemia due to malabsorption of iron and menorrhagia. Hypothyroidism is a common but under-recognized and under-diagnosed condition in the Persian Gulf countries. Moreover, the evaluation of the effect of hypothyroidism on vitamin D and iron levels is inadequate. Identifying this bi-deficiency is essential so that doctors can identify and treat them earlier and reduce the deficiency-related complications, and supplements can be given to prevent further health complications like osteoporosis and iron deficiency anaemia.

Hyperoxia in Depression

Several studies of normobaric hyperoxia in some neurological conditions have demonstrated clinical benefits. Oxygen enriched air may increase oxygen pressure in brain tissue and have biochemical effects such as on brain erythropoietin gene expression, even in patients without lung disease.

Hyperoxia in depression

IntroductionSeveral studies of normobaric hyperoxia in some neurological conditions have demonstrated clinical benefits. Oxygen enriched air may increase oxygen pressure in brain tissue and have biochemical effects such as on brain erythropoietin gene expression, even in patients without lung disease.ObjectivesThis pilot, randomized, double-blind study examined the efficacy of normobaric hyperoxia as a treatment for depression.MethodsFifty-five consenting patients aged 18-65 years with mild to moderate depression were included in the study. Participants underwent a psychiatric inclusion assessment and a clinical evaluation by a psychiatric nurse at baseline, 2 and 4 weeks after commencement of study intervention. Participants were randomly assigned to normobaric hyperoxia of 35% fraction of inspired oxygen or 21% fraction of inspired oxygen (room air), through a nasal tube, for 4 weeks, during the night. Patients were rated blindly using the Hamilton Rating Scale for Depression (HRSD); Clinical Global Impression (CGI) questionnaire; Sheehan Disability Scale (SDS).Results The present study showed a significant improvement in HRSD (p&lt;0.0001), CGI (p&lt;0.01) and in SDS (p&lt;0.05) among patients with depression who were treated with oxygen-enriched air, as compared to patients who were treated with room air. In CGI, 69% of the patients who were treated with oxygen-enriched air improved compared to 23% patients who were treated with room air.ConclusionsThis small pilot study showed a beneficial effect of normobaric hyperoxia on some symptoms of depression.DisclosureNo significant relationships.

Kidney pericyte hypoxia-inducible factor regulates erythropoiesis but not kidney fibrosis

Prolyl hydroxylase domain enzyme (PHD) inhibitors are effective in the treatment of chronic kidney disease (CKD)-associated anemia by stabilizing hypoxia inducible factor (HIF), thereby increasing erythropoietin and consequently erythropoiesis. However, concern for CKD progression needs to be addressed in clinical trials. Although pre-clinical studies showed an anti-inflammatory effect in kidney disease models, the effect of PHD inhibitors on kidney fibrosis was inconsistent probably because the effects of HIF are cell type and context dependent. The major kidney erythropoietin-producing cells are pericytes that produce erythropoietin through HIF-2α-dependent gene transcription. The concern for the impact of HIF in pericytes on kidney fibrosis arises from the fact that pericytes are the major precursor cells of myofibroblasts in CKD. Since cells expressing Gli1 fulfill the morphologic and anatomic criteria for pericytes, we induced Gli1+ cell-specific HIF stabilization or knockout to study the impact of HIF in pericytes on kidney pathology of mice with or without fibrotic injury induced by unilateral ureteral obstruction. Compared with the littermate controls, mice with pericyte-specific HIF stabilization due to von Hippel-Lindau protein or PHD2 knockout showed increased serum erythropoietin and polycythemia rather than a discernible difference in kidney fibrosis. Compared with Gli1+ pericytes sorted from littermate controls, Gli1+ pericytes sorted from PHD2 knockout mice showed increased erythropoietin gene expression rather than discernible changes in Col1a1 or Acta2 expression. Furthermore, pericyte-specific knockout of HIF-1α or HIF-2α did not affect kidney fibrosis. Thus, our study supports the absence of negative effects of PHD inhibitors on kidney fibrosis of mice despite HIF stabilization in pericytes.

Regulated Basal, Inducible, and Tissue-Specific Human Erythropoietin Gene Expression in Transgenic Mice Requires Multiple cis DNA Sequences

Erythropoietin (Epo) gene expression in kidney and liver is inducible by anemia. To localize the sequences necessary for regulated expression of the Epo gene, we constructed transgenic mice containing five human Epo gene constructs and examined Epo expression under basal conditions and with anemia. Mice containing the Epo gene with 0.3 kb of 5' flanking sequence, 0.7 kb of 3' flanking sequence, and either all introns or only intron I alone were polycythemic, had Epo expression in various tissues (including non-Epo-producing tissues), and induction only in liver. In contrast, mice containing the Epo gene with 8.5 kb of 3' flanking sequence and either 9.5 or 22 kb of 5' flanking sequence had basal expression at low levels in appropriate tissues and were less likely to be markedly polycythemic. Mice with the smaller of these two constructs had induction only in the liver, whereas those with the larger construct had induction in the kidney and liver. These studies indicate that sequences sufficient for induction in the liver are located in close proximity to the Epo gene, including the immediate 5' and 3' flanking sequence and the first intron. They also indicate that sequences required for induction in the kidney are located more than 9.5 kb 5' to the gene. Furthermore, comparison of these and prior transgenic studies suggest that sequences that limit the basal expression of the Epo gene are located downstream of the gene. We conclude that multiple cis DNA sequences are required for regulated Epo gene expression.

Prolonged astrocyte-derived erythropoietin expression attenuates neuronal damage under hypothermic conditions

BackgroundHypoxic-ischemic encephalopathy (HIE) has a high morbidity rate and involves severe neurologic deficits, including cerebral palsy. Therapeutic hypothermia (TH) has been shown to decrease the mortality rate and provide neuroprotection in infants with HIE. However, death and disability rates in HIE infants treated with TH remain high. Although the cellular mechanism of the neuroprotective effect of TH remains unclear, astrocytic erythropoietin (EPO) is known to be a key mediator of neuroprotection under hypoxic conditions. In the present study, we investigated the hypothermia effect on EPO expression in astrocytes and determined whether hypothermia attenuates neuronal damage via EPO signaling.MethodsAstrocytes derived from rat cerebral cortex were cultured under oxygen/glucose deprivation (OGD). The expression of EPO and hypoxia-inducible factor (HIF), a transcription factor of EPO, was assessed. After OGD, astrocytes were cultured under normothermic (37 °C) or hypothermic (33.5 °C) conditions, and then EPO and HIF expression was assessed. After OGD, rat cortical neurons were cultured in astrocyte-conditioned medium (ACM) derived from the hypothermic group, and neuronal apoptosis was evaluated.ResultsOGD induced EPO mRNA and protein expression, although at lower levels than hypoxia alone. HIF-1α and HIF-2α protein expression increased under hypoxia alone and OGD, although OGD increased HIF-2α protein expression less than hypoxia alone. EPO gene and protein expression after OGD was significantly higher under hypothermia. Moreover, expression of HIF-1α and HIF-2α protein was enhanced under hypothermia. In the presence of ACM derived from hypothermic astrocytes following OGD, the number of cleaved caspase 3 and TdT-mediated dUTP nick-end labeling-positive apoptotic neurons was lower than in the presence of ACM from normothermic astrocytes following OGD. Blockade of EPO signaling using anti-EPO neutralization antibody attenuated the anti-apoptotic effect of ACM derived from hypothermic astrocytes following OGD.ConclusionsHypothermia after OGD stabilized HIF-EPO signaling in astrocytes, and upregulated EPO expression could suppress neuronal apoptosis. Investigating the neuroprotective effect of EPO from astrocytes under hypothermic conditions may contribute to the development of novel neuroprotection-based therapies for HIE.

Impact of Thyroid Dysfunction on Red Cell Indices in a Tertiary Care Hospital

Background: The role of thyroid gland is to regulate the hematopoiesis in the bone marrow, which is carried out by inducing erythropoietin gene expression. The study aimed to compare red cell indices among different thyroid dysfunction disorders patients in our setup. Methods: This retrospective observational study was conducted in Ziauddin University Hospital, Karachi in Clifton campus from January 2017 to September 2017. To maintain confidentiality, patient’s identification was deleted. Total number of recruited patients was 485, out of which 117 were labeled as hyperthyroid, 169 were hypothyroid and 199 were euthyroid. Subjects for all three groups were between 20-60 years old. TSH level of patients were determined by VITROS® ECiQ immunoassay analyzer by Enhanced chemiluminescence technique. Data analysis was done on SPSS 20 while, mean and Standard deviation were calculated for quantitative variables. Percentages and frequencies were calculated for categorical variables and an independent t-test was applied to see significant differences among the groups. Results: Comparison between hyperthyroid and hypothyroid groups revealed a statistically significant difference in the mean hemoglobin (p=0.036) and hematocrit (p=0.022). A statistically significant difference was also found in the RBC count (p=0.043) and hematocrit (p=0.032) while comparing hyperthyroid and euthyroid groups. There was no statistical difference between hypothyroid and euthyroid patients for any of the hematological parameters. Conclusion: There was a proven association between thyroid dysfunction and erythropoiesis, which caused hematological indices to fluctuate, therefore hematological parameters, should be monitored in patients with thyroid diseases.

Distal and proximal hypoxia response elements cooperate to regulate organ-specific erythropoietin gene expression.

While it has been well-established that distal hypoxia response elements (HRE) regulate hypoxia-inducible factor (HIF) target genes such as erythropoietin (Epo), an interplay between multiple distal and proximal (promoter) HRE has not yet been described. Hepatic Epo expression is regulated by an HRE located downstream of the EPOgene, but this 3' HRE is not essential for renal EPO gene expression. We previously identified a 5' HRE and could show that both HRE direct exogenous reporter gene expression. Here, we show that, whereas in hepatic cells the 3' but not the 5' HRE is required, in neuronal cells both the 5' and 3' HRE contribute to endogenous Epo induction. Moreover, two novel putative HRE were identified in the EPO promoter. In hepatoma cells, HIF interacted mainly with the distal 3' HRE, but in neuronal cells, HIF most strongly bound the promoter, bound to a lesser extent the 3' HRE, and did not bind the 5' HRE. Interestingly, mutation of either of the two distal HRE abrogated HIF binding to the 3' and promoter HRE. These results suggest that a canonical functional HRE can recruit multiple transcription factors (not necessarily HIF) to mediate HIF binding to different distant HRE in an organ-specific manner.

Mechanisms of hypoxia signalling: new implications for nephrology.

Studies of the regulation of erythropoietin (EPO) production by the liver and kidneys, one of the classical physiological responses to hypoxia, led to the discovery of human oxygen-sensing mechanisms, which are now being targeted therapeutically. The oxygen-sensitive signal is generated by 2-oxoglutarate-dependent dioxygenases that deploy molecular oxygen as a co-substrate to catalyse the post-translational hydroxylation of specific prolyl and asparaginyl residues in hypoxia-inducible factor (HIF), a key transcription factor that regulates transcriptional responses to hypoxia. Hydroxylation of HIF at different sites promotes both its degradation and inactivation. Under hypoxic conditions, these processes are suppressed, enabling HIF to escape destruction and form active transcriptional complexes at thousands of loci across the human genome. Accordingly, HIF prolyl hydroxylase inhibitors stabilize HIF and stimulate expression of HIF target genes, including the EPO gene. These molecules activate endogenous EPO gene expression in diseased kidneys and are being developed, or are already in clinical use, for the treatment of renal anaemia. In this Review, we summarize information on the molecular circuitry of hypoxia signalling pathways underlying these new treatments and highlight some of the outstanding questions relevant to their clinical use.

Placental erythropoietin expression is upregulated in growth-restricted fetuses with abnormal umbilical artery Doppler findings: a case\u2013control study of monochorionic twins

BackgroundWe previously reported that fetal plasma erythropoietin (EPO) concentrations are significantly increased in growth-restricted fetuses with abnormal umbilical artery (UA) Doppler. During hypoxia in an ovine model, the primary site of fetal EPO synthesis was switched from the kidneys to the placenta. Therefore, we designed this study to evaluate human placental EPO gene expression and the correlation to fetal serum EPO concentration in growth-restricted fetuses in a monochorionic (MC) twin model.MethodsIn MC twin pairs, selective intrauterine growth restriction (sIUGR) was defined as the presence of (i) birth weight discordance of > 20% and (ii) a smaller twin with a birth weight less than the 10th percentile. Fetal UA and middle cerebral artery (MCA) Doppler were checked within 1 week before delivery. An abnormal UA Doppler was defined as persistently absent or reverse end-diastolic flow. Cerebroplacental ratio (CPR) was defined as MCA-pulsatility index (PI)/UA-PI. Fetal plasma EPO concentrations were measured in cord blood, and EPO gene expression was assayed in each twin’s placental territory. The intertwin plasma EPO ratio was calculated as the cord plasma EPO level of the smaller (or sIUGR) twin divided by the EPO concentration of the larger (or appropriate-for-gestational-age (AGA)) twin, and the intertwin placental EPO gene expression ratio was calculated similarly.ResultsTwenty-six MC twins were analyzed, including normal twins (Group 1, n = 9), twins with sIUGR without UA Doppler abnormalities (Group 2, n = 9), and twins with sIUGR and UA Doppler abnormalities (Group 3, n = 8). The CPRs of smaller (sIUGR) fetuses were significantly decreased in Group 3 MC twins (p < 0.001), but not significantly different between Group 1 and Group 2. The highest fetal plasma EPO ratio and placental EPO gene expression ratio were identified in Group 3 MC twins (p < 0.001). The placental EPO gene expression ratios were significantly correlated with the fetal plasma EPO ratios (Pearson’s correlation test, p = 0.004).ConclusionThis study provides evidence of increased placental EPO expression in MC twin fetuses with sIUGR and abnormal UA Doppler. Future studies are needed to confirm the similar role of placental EPO in severe IUGR singletons.

Carbamoylated erythropoietin induces a neurotrophic gene profile in neuronal cells

Erythropoietin (EPO), a cytokine molecule, is best-known for its role in erythropoiesis. Preclinical studies have demonstrated that EPO has robust neuroprotective effects that appear to be independent of erythropoiesis. It is also being clinically tested for the treatment of neuropsychiatric illnesses due to its behavioral actions. A major limitation of EPO is that long-term administration results in excessive red blood cell production and increased blood viscosity. A chemical modification of EPO, carbamoylated erythropoietin (CEPO), reproduces the behavioral response of EPO in animal models but does not stimulate erythropoiesis. The molecular mechanisms involved in the behavioral effects of CEPO are not known. To obtain molecular insight we examined CEPO induced gene expression in neuronal cells. PC-12 cells were treated with CEPO followed by genome-wide microarray analysis. We investigated the functional significance of the gene profile by unbiased bioinformatics analysis. The Ingenuity pathway analysis (IPA) software was employed. The results revealed activation of functions such as neuronal number and long-term potentiation. Regulated signaling cascades included categories such as neurotrophin, CREB, NGF and synaptic long-term potentiation signaling. Some of the regulated genes from these pathways are CAMKII, EGR1, FOS, GRIN1, KIF1B, NOTCH1. We also comparatively examined EPO and CEPO-induced gene expression for a subset of genes in the rat dentate gyrus. The CEPO gene profile shows the induction of genes and signaling cascades that have roles in neurogenesis and memory formation, mechanisms that can produce antidepressant and cognitive function enhancing activity.

Physiology and pathophysiology of renal erythropoietin-producing cells.

Anemia is a common complication and contributes to increased morbidity and mortality in chronic kidney disease (CKD) patients. Whereas there has been a significant improvement of understanding the underlying mechanism of erythropoiesis, the treatment of renal anemia is still restricted to erythropoietin (EPO)-stimulating agents. The purpose of this article is to review the physiology of erythropoiesis, functional role of EPO and underlying molecular and cellular basis that regulate EPO production. Regulation of EPO production is at mRNA level. When anemia or hypoxia occurs, transcriptional factor, hypoxia-inducible factor (HIF), binds to EPO 5' hypoxic response element and EPO gene transcription increases. The renal EPO is mainly produced by pericytes. In CKD, pericytes transdifferentiate to myofibroblasts, and subsequently the ability of EPO production decreases, leading to renal anemia. Recent experimental and clinical studies show the promising efficacy of prolyl hydroxylase inhibitors in renal anemia through increasing EPO production by stabilizing HIF. Recent advances on epigenetics create a new field to study EPO gene expression at chromatin level. We will discuss the role of demethylating agent on restoring EPO expression, providing a novel approach to the treatment of renal anemia.

Chronic cigarette smoking-induced oxidative/nitrosative stress in human erythrocytes and platelets

Cigarette smoke contains a number of highly unstable free radicals and these free radicals enhance reactive oxygen species (ROS) and reactive nitrogen species (RNS) production leading to oxidative/nitrosative stress. Increased oxidative/nitrosative stress plays an important role in the onset of various vascular diseases. The aim of this study is to evaluate smoking-induced nitrosative and oxidative stress and the role of hypoxia inducible factor 1 alpha (HIF-1α) in erythrocytes and platelets. For this study human male volunteers aged 35±8 years were recruited and divided into two groups, namely controls and smokers (12±2 cigarettes per day for 7-10 years). Blood was collected and analyzed for various metabolites and enzymes. Results showed a decreased plasma vitamin C and reduced glutathione (GSH) with increased lipid peroxidation, carbonyl groups, iron, hemoglobin and glycated hemoglobin content in smokers. Furthermore, smokers showed higher nitrite/nitrate levels with increased eNOS protein expression in erythrocytes, in contrast, platelets showed lower nitrite/nitrate levels with decreased eNOS protein expression compared to controls. Moreover, smokers showed diminished GSH and the activities of superoxide dismutase (SOD) glutathione peroxidase (GPx) and catalase (CAT) in both erythrocytes and platelets compared to controls. Real time PCR analysis of whole blood from smokers showed increased HIF-1α and erythropoietin (EPO) gene expression compared to controls. In summary, smoking increased oxidative stress by decreasing antioxidant status in both red cells and platelets. Besides, smokers showed up-regulated HIF-1α gene expression, which inturn drives the transcription of eNOS and EPO genes under oxidative/nitrosative stress conditions.