Renal Erythropoietin Production Research Articles

The drug-specific properties of hypoxia-inducible factor-prolyl hydroxylase inhibitors in mice reveal a significant contribution of the kidney compared to the liver to erythropoietin induction

AimsKidney disease often leads to anemia due to a defect in the renal production of the erythroid growth factor erythropoietin (EPO), which is produced under the positive regulation of hypoxia-inducible transcription factors (HIFs). Chemical compounds that inhibit HIF-prolyl hydroxylases (HIF-PHs), which suppress HIFs, have been developed to reactivate renal EPO production in renal anemia patients. Currently, multiple HIF-PH inhibitors, in addition to conventional recombinant EPO reagents, are used for renal anemia treatment. This study aimed to elucidate the therapeutic mechanisms and drug-specific properties of HIF-PH inhibitors. Methods and key findingsGene expression analyses and mass spectrometry revealed that HIF-PH inhibitors (daprodustat, enarodustat, molidustat, and vadadustat) alter Epo gene expression levels in the kidney and liver in a drug-specific manner, with different pharmacokinetics in the plasma and urine after oral administration to mice. The drug specificity revealed the dominant contribution of EPO induction in the kidneys rather than in the liver to plasma EPO levels after HIF-PH inhibitor administration. We also found that several HIF-PH inhibitors directly induce duodenal gene expression related to iron intake, while these drugs indirectly suppress hepatic hepcidin expression to mobilize stored iron for hemoglobin synthesis through induction of the EPO-erythroferrone axis. SignificanceRenal EPO induction is the major target of HIF-PH inhibitors for their therapeutic effects on erythropoiesis. Additionally, the drug-specific properties of HIF-PH inhibitors in EPO induction and iron metabolism have been shown in mice, providing useful information for selecting the proper HIF-PH inhibitor for each renal anemia patient.

Abstract 378: PHD3 dependent stabilization of β3-adrenoceptor induces HIF-1αactivation in Ewing sarcoma

Abstract Hypoxia is a condition of oxygen deficiency which occurs in most growing solid tumors and stimulates a cascade of cell signals through a family of transcription factors named as hypoxia inducible factors (HIFs) that transactivate several regulatory genes involved in tumor proliferation. β3-adrenoceptors (β3-ARs) are involved in several hypoxic scenarios and in pathological conditions where hypoxia leads to important steps for cancer progression. Studies showed that β-AR blockade of mice suppressed hypoxia induction of renal HIF-1α accumulation, erythropoietin production, and erythropoiesis in vivo. In this work we assumed that through PHD3 activity, β3-AR mediates hypoxia sensing needed for HIF-1α stabilization, thus we investigated a putative correlation between β3-AR/HIF-1α and PHD3. Data showed a similar outcome of β3-ARs and HIF-1α at short time of hypoxia, and that β3-AR antagonist, SR59230A reduced HIF-1α protein expression under hypoxia. β3-AR silencing under hypoxia revealed an evident reduction of HIF-1α protein expression that confirmed the β3-AR modulation of HIF-1α expression. SR59230A treatment strongly reduced the HIF-1α target genes as GLUT1, HK-2 and HIF-1α expression at long time treatment confirming the β3-AR modulation of HIF-1α transcriptional activity. Conversely, the HIF-1α-transcriptional inhibitor Topotecan did not affect β3-AR expression confirming that β3-AR mediates HIF-1α activation. Immunofluorescence and nuclear-cytoplasmic fragmentation showed that β3-AR co-localized with the nucleus under hypoxia, more than normoxia, and presence of both β3-AR and HIF-1α in the nucleus. Co-immunoprecipitation of β3-AR/HIF-1α revealed that under hypoxia, HIF-1α dissociates from β3-AR binding, but this process was abrogated by SR59230A. HIF-1α, released under hypoxia from the link with β3-AR, can play its transcriptional activity in the nucleus, while the binding with β3-AR blocks its transcriptional activity. Moreover, the β3-AR upregulation under hypoxia occurs trough an early inhibition of PHD3 activity that did not influence HIF-1α expression. Hypoxic PHD2 inhibition results after PHD3 leading to HIF-1α upregulation. Moreover, the blockade β3-AR by SR59230A, inhibited HIF-1α upregulation by increasing PHD2 activity. Citation Format: Amada Pasha, Laura Zocca, Francesco Carrozzo, Cristina Banella, Rachele Amato, Annalisa Tondo, Claudio Favre, Maura Calvani. PHD3 dependent stabilization of β3-adrenoceptor induces HIF-1αactivation in Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 378.

Drugs activating hypoxia-inducible factors correct erythropoiesis and hepcidin levels via renal EPO induction in mice

AbstractThe erythroid growth factor erythropoietin (EPO) is mainly produced by the kidneys in adult mammals and induces expansion of erythroid cells and iron use for hemoglobin synthesis. The liver also produces EPO at a lower level than the kidneys. Renal and hepatic EPO production is fundamentally regulated by hypoxia-inducible transcription factors (HIFs) in a hypoxia/anemia-inducible manner. Recently, small compounds that activate HIFs and EPO production in the kidneys by inhibiting HIF-prolyl hydroxylases (HIF-PHIs) have been launched to treat EPO-deficiency anemia in patients with kidney disease. However, the roles of the liver in the HIF-PHI–mediated induction of erythropoiesis and iron mobilization remain controversial. Here, to elucidate the liver contributions to the therapeutic effects of HIF-PHIs, genetically modified mouse lines lacking renal EPO-production ability were analyzed. In the mutant mice, HIF-PHI administration marginally increased plasma EPO concentrations and peripheral erythrocytes by inducing hepatic EPO production. The effects of HIF-PHIs on the mobilization of stored iron and on the suppression of hepatic hepcidin, an inhibitory molecule for iron release from iron-storage cells, were not observed in the mutant mice. These findings demonstrate that adequate induction of EPO mainly in the kidney is essential for achieving the full therapeutic effects of HIF-PHIs, which include hepcidin suppression. The data also show that HIF-PHIs directly induce the expression of duodenal genes related to dietary iron intake. Furthermore, hepatic EPO induction is considered to partially contribute to the erythropoietic effects of HIF-PHIs but to be insufficient to compensate for the abundant EPO induction by the kidneys.

Abstract 4808: Hypoxic HIF-1α stabilization dependent on β3-adrenoceptor localization in Ewing sarcoma

Abstract Hypoxia is a condition of oxygen deficiency which occurs in most growing solid tumors and stimulates a cascade of cell signals through a family of transcription factors named as hypoxia inducible factors (HIFs) that transactivate several regulatory genes involved in tumor proliferation. β3-adrenoceptors (β3-ARs) are involved in several hypoxic scenarios and in pathological conditions where hypoxia leads to important steps for cancer progression. Studies showed that β-AR blockade of mice suppressed hypoxia induction of renal HIF-1α accumulation, erythropoietin production, and erythropoiesis in vivo. In this work we assumed that β3-AR mediates hypoxia sensing and that it was necessary for HIF-1α stabilization thus we investigated a putative correlation between β3-AR/HIF-1α. Data showed a similar outcome of β3-ARs and HIF-1α at short time of hypoxia, and that β3-AR antagonist, SR59230A reduced HIF-1α protein expression under hypoxia. β3-AR silencing under hypoxia revealed an evident reduction of HIF-1α protein expression that confirmed the β3-AR modulation of HIF-1α expression. SR59230A treatment strongly reduced the HIF-1α target genes as GLUT1, HK-2 and HIF-1α expression at long time treatment confirming the β3-AR modulation of HIF-1α transcriptional activity. Conversely, the HIF-1α-transcriptional inhibitor Topotecan did not affect β3-AR expression confirming that is β3-AR that mediates HIF-1α activation. Immunofluorescence analysis showed that β3-AR co-localized with the nucleus under hypoxia more than normoxia. These results were confirmed by nuclear-cytoplasmic fragmentation that showed the presence of both β3-AR and HIF-1α proteins in the nucleus under hypoxia. Co-immunoprecipitation of β3-AR/HIF-1α revealed that under hypoxia, HIF-1α dissociates from β3-AR binding, but this process was abrogated by SR59230A. HIF-1α, released under hypoxia from the link with β3-AR, can play its transcriptional activity in the nucleus, while the binding with β3-AR blocks its transcriptional activity. Moreover, β3-AR regulation on HIF-1α was exerted through PHD2 activity at short time as SR59230A treatment under hypoxia increased the PHD2 protein expression but not at long time treatment, thus showing a different regulation of HIF-1α at different time points. In conclusion, the β3-AR upstream of the signaling β3-AR/HIF-1α axis exerts its role by PHD2 activity. Citation Format: Amada Pasha, Claudia Masi, Francesco Carrozzo, Martina Rosati, Alessia Boaretto, Alessandro Pini, Claudio Favre, Maura Calvani. Hypoxic HIF-1α stabilization dependent on β3-adrenoceptor localization in Ewing sarcoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4808.

Prevalence of Anemia in Chronic Kidney Disease (CKD) Patients on Conservative Treatment in Benghazi- 2022

Background: Anemia is one of the most common and significant complications of chronic kidney disease (CKD) which is related to decreases in the glomerular filtration rate (GFR). Anemia is generally defined as a hemoglobin count of less than 13.0 g/ld in men and less than 12.0 g/dL in premenopausal women. Anemia of CKD is of a multifactorial origin; the widely accepted etiology being decreased renal production of erythropoietin (EPO). Since the kidney's production of erythropoietin serves as the primary stimulus for the production of red blood cells, CKD patients have lower levels of erythropoietin, which in turn can cause anemia. Anaemia in CKD patients is normocytic, normochromic and hypoproliferative.
 Aim: Determination of proportion and risk factors of anemia in CKD patients.
 Materials and method: A cross-sectional sectional study with a sample size of 91 CKD patients on conservative treatment. A questionnaire was used to interview patients who had been enrolled in the study. It included sociodemographic data, body mass index (BMI), past medical history, drug history, and laboratory data. 
 Results: The overall prevalence of anemia was 35.2% among CKD patients on conservative treatment. The mean age of patients was 62.9±14.65 SD years and the mean BMI was 27.65±5.5SD. Most of the patients were from the OPD clinic (GFR>15 ml/min/1.73 m2). 60% of the patients were hypertensive and diabetic. Hemoglobin (HB) levels were 10.52 ± 2.7 SD. According to to mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH), the type of anemia observed was normocytic and normochromic. Most of the patients were commonly prescribed an oral and an injectable iron supplement.
 Conclusion: Anemia was prevalent in CKD patients and the severity increased with the degree of renal damage; however, it is sub-optimally managed. Screening and management of anemia for patients with renal disease should focus more on patients with lower GFR.

FREQUENCY OF IRON DEFICIENCY ANEMIA IN NON-DIALYSIS CHRONIC KIDNEY PATIENTS

Background: Iron deficiency anemia (IDA) is the most common type of anemia. In chronic kidney disease (CKD) patients, it’s a significant burden and becomes more prevalent with decreasing GFR. Though, erythropoietin deficiency remains the major cause of anemia in CKD patients due to decreased renal erythropoietin production, yet the frequency of IDA in pre-dialysis CKD patients has not been well established in Pakistan. Objective: To determine the frequency of IDA in pre-dialysis CKD patients. Materials and Methods: 188 pre-dialysis CKD patients of age 18-75 and both genders were included. Patients having obvious causes of anemia were excluded. The percentage of patients with IDA in pre-dialysis CKD was then determined during OPD follow up. Results: Mean age was 46.03±12.24 years. Out of 188 patients, 102 (54.26%) were males with male-female ratio of 1.2:1. The frequency of IDA in pre-dialysis CKD patients was found in 73 (38.83%) patients. Conclusion: Study concluded that frequency of IDA in pre-dialysis CKD patients is high and close attention to the causes and its replacement may improve the patient outcome. Keywords: CKD, Pre-dialysis , IDA, anemia

A STUDY TO EVALUATE THE EFFECT OF ANAEMIA IN TYPE-2 DIABETIC PATIENTS

Introduction: As the tribulation of diabetes escalates, developing countries like India is expected to be the diabetic capital in the world in coming years. Diabetes Mellitus progressively results in various complications including both microvascular and macrovascular disorders. The nephropathy undermines the renal production of erythropoietin, positively contributing to an increased anaemic framework. However, anaemia in type 2 diabetic patients is often untended. Aims And Objectives: • To correlate the levels of haemoglobin with the degree of glycaemic control (HbA1c>6.5% vs HbA1c<6.5%) • To determine the morphology and severity of anaemia in type 2 diabetic patients. • To know prevalence of other comorbidities as a result of anaemia and diabetes. Materials And Methods: A prospective observational study was conducted in 100 type 2 diabetic patients visiting the Out Patient Department in Acs Medical College and Hospital, Chennai. Haemoglobin and red cell indices were estimated. Comorbidities like hypertension, chronic kidney disease, arthritis and retinopathy were recorded. Peripheral blood smear examination was done using leishman's stain. Ion exchange chromatography was used to measure the HbA1c levels. Results: In the poor glycaemic control group, a signicant decrease in the haemoglobin levels was noted especially in females and elderly population. Microcytic Hypochromic Anaemia was the most prevalent which was of mild to moderate severity. Predominantly reduced iron stores in Microcytic Hypochromic Anaemia were attributed to increased HbA1c levels. The poor control of diabetes when associated with anaemia, were also found to have comorbidities like hypertension, chronic kidney disease, arthritis and retinopathy. Conclusion: To conclude, though anaemia is signicantly prevalent in diabetic patients, it is often neglected. In accordance with the study, poor glycaemic control is the result of increased glycation of haemoglobin A1c (HbA1c) due to reduced iron stores. Hence in diabetic patients, it would be benecial to assess haemoglobin levels often, for better quality of life

Bilateral Nephromegaly in a Child with Severe Iron-Deficiency Anemia

Nephromegaly in childhood can result from a wide variety of causes, yet iron-deficiency anemia has not been previously described. We report a child with severe iron-deficiency anemia associated with transient bilateral nephromegaly. We hypothesize that increased renal production of erythropoietin as well as greater cardiac output with subsequent glomerular hyperfiltration secondary to critical anemia explained the observed nephromegaly. The normalization of kidney size following resolution of anemia supports this hypothesis. Our case report suggests an additional etiology of bilateral nephromegaly in the pediatric population and thus merits attention among physicians.

Efficacy and Safety of Molidustat for Anemia in ESA-Naive Nondialysis Patients: A Randomized, Phase 3 Trial

Introduction: Molidustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that predominantly induces renal production of erythropoietin (EPO). Molidustat was evaluated for the treatment of anemia associated with chronic kidney disease (CKD) in the “Molidustat Once Daily Improves Renal Anemia by Inducing EPO” (MIYABI) program, which comprises 5 phase 3 clinical trials. The present MIYABI Non-Dialysis Correction (ND-C) study investigated the efficacy and safety of molidustat in Japanese patients with renal anemia who were not undergoing dialysis and were not receiving erythropoiesis-stimulating agent (ESA) treatment. Methods: This was a 52-week, randomized (1:1), open-label, active-control, parallel-group, multicenter, phase 3 study in Japanese patients with renal anemia associated with CKD (stages 3–5). Molidustat or the ESA darbepoetin alfa (hereinafter referred to as darbepoetin) were initiated at 25 mg once daily or 30 μg every 2 weeks, respectively, and doses were regularly titrated to correct and to maintain hemoglobin (Hb) levels in the target range of ≥11.0 g/dL and <13.0 g/dL. The primary efficacy outcome was the mean Hb level and its change from baseline during the evaluation period (weeks 30–36). The safety outcomes included evaluation of all adverse events. Results: In total, 162 patients were randomized to receive molidustat (n = 82) or darbepoetin (n = 80). Baseline characteristics were generally well balanced between treatment groups. The mean (standard deviation) Hb levels at baseline were 9.84 (0.64) g/dL for molidustat and 10.00 (0.61) g/dL for darbepoetin. The mean (95% confidence interval [CI]) for mean Hb levels during the evaluation period for molidustat (11.28 [11.07, 11.50] g/dL) and darbepoetin (11.70 [11.50, 11.90] g/dL) was within the target range. Based on a noninferiority margin of 1.0 g/dL, molidustat was noninferior to darbepoetin in the change in mean Hb level during the evaluation period from baseline; the least-squares mean (95% CI) difference (molidustat-darbepoetin) was −0.38 (−0.67, −0.08) g/dL. The proportion of patients who reported at least 1 treatment-emergent adverse event (TEAE) was 93.9% for molidustat and 93.7% for darbepoetin. Most TEAEs were mild (54.9% for molidustat and 63.3% for darbepoetin) or moderate (22.0% for molidustat and 22.8% for darbepoetin) in intensity. There were 3 deaths in the molidustat group and 1 in the darbepoetin group. Discussion/Conclusion: In the MIYABI ND-C study, molidustat appeared to be an efficacious and generally well-tolerated alternative to darbepoetin for the treatment of renal anemia in Japanese patients who were not undergoing dialysis and were not receiving ESA treatment.

Multiorgan Signaling Mobilizes Tumor-Associated Erythroid Cells Expressing Immune Checkpoint Molecules.

Hematopoietic-derived cells are integral components of the tumor microenvironment and serve as critical mediators of tumor-host interactions. Host cells derived from myeloid and lymphoid lineages perform well-established functions linked to cancer development, progression, and response to therapy. It is unclear whether host erythroid cells also contribute to shaping the path that cancer can take, but emerging evidence points to this possibility. Here, we show that tumor-promoting environmental stress and tumor-induced hemodynamic changes trigger renal erythropoietin production and erythropoietin-dependent expansion of splenic erythroid cell populations in mice. These erythroid cells display molecular features indicative of an immature erythroid phenotype, such as the expression of both CD71 and TER119 and the retention of intact nuclei, and express genes encoding immune checkpoint molecules. Nucleated erythroid cells with similar properties are present in mouse and human tumor tissues. Antibody-mediated erythropoietin blockade reduces tumor-responsive erythroid cell induction and tumor growth. These findings reveal the potential of tumor-induced erythropoietin and erythroid cells as targets for cancer treatment. IMPLICATIONS: : Our study identifies erythropoietin and erythroid cells as novel players in tumor-host interactions and highlights the involvement of multiorgan signaling events in their induction in response to environmental stress and tumor growth.

NOVEL IRON BIOMARKERS IN CHRONIC KIDNEY DISEASE

CKD is one of the fastest growing causes of death in the world and in 2040, it is estimated that it will be in the top five causes of death. In order to slow down this process, it is necessary to improve prevention, inhibit development and treat complications including anemia. Anemia is one of the common complication of chronic kidney disease (CKD), which is a significant clinical problem. It is most often the result of decreased renal production of erythropoietin and / or iron deficiency. Iron deficiency anemia is one of the most common problems in CKD that increases mortality. In order to successfully treat anemia in CKD with erythropoiesis-stimulating agentsand (ESA) and iron substitution, it is necessary to determine iron iron level. The diagnosis of iron deficiency anemia in patients with CKD is complicated due to the relatively low predictive ability of routine serum iron markers (e.g., ferritin and transferrin saturation) and more invasive measurements such as bone marrow iron stores. In the review novel biomarkers of iron metabolism are discussed such as hypoxia-inducible factor, erythroferon, growth differentiation factor 15 etc. with their possible clinical relevance.

Prevalence of Anaemia in Patients with Type-2 Diabetes Mellitus in the Absence of Renal Impairment: A Cross-sectional Study

Introduction: Despite an increasing incidence of diabetic nephropathy, undermining the renal production of Erythropoietin (EPO), there are significant number of studies being reported with anaemia among diabetic patients with renal insufficiency, implicating numerous theoretical pathogenesis. Its impact being ignored over the years among Indian contexts, women and men in rural Southern India are particularly vulnerable to anaemia. The associated risk factors and occurrence of anaemia in Type-2 Diabetes Mellitus (T2DM) can be seen even in the absence of renal insufficiency. Aim: To determine the prevalence of anaemia in T2DM patients with normal renal function and assessment of its association with sociodemographic characteristics, biochemical and haematological variables. Materials and Methods: A descriptive cross-sectional study was conducted for a period of six months from December 2018 to May 2019 on total of 150 patients with T2DM, attending the Outpatient Department, Rajarajeswari Medical College and Hospital, Bangalore, India. All the patients of either sex, aged between 18-60 years, with a duration of Diabetes Mellitus (DM) more than five years, with no renal involvement, were included in the study. All statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 20.0. The Chi-square test, Z-test was used for data analysis. Results: Among the 150 subjects, 86 (57.3%) were classified to be anaemic, with a mean age of 53 years whereas, 64 (42.6%) were classified as non anaemics with a mean age of 50 years. The mean duration of diabetes was found to be 10.5 years among anaemics and 9.7 years among non anaemics. Compared to non anaemics subjects, drug therapy with both Oral Hypoglycaemic Agents (OHA) and insulin showed a statistically significant difference among diabetic subjects with anaemia. The high prevalence of normocytic anaemia (52.3%) suggests the importance of non renal causes of anaemia in diabetic patients. Conclusion: Patients with T2DM have an independent risk for anaemia irrespective of renal insufficiency, posing a significant adverse effect on the quality of life and the progression of the underlying disease with high cardiovascular morbidity and mortality. Hence, management of diabetic patients should include mandatory routine haematological tests, with consideration of advancing age and poor glycaemic control.

P0377THE RELATIONSHIP BETWEEN SEVERITY OF INTERSTITIAL FIBROSIS AND ANEMIA IN PATIENT WITH PRIMARY GLOMERULONEPHRITIS: THE DATA FROM TSN-GOLD WORKING GROUP

Abstract Background and Aims Anemia is one of the most important complications in chronic renal disease and inadequate erythropoietin production is the most important reason for anemia. Fibrosis of renal interstitium may be associated with inadequate synthesis of erythropoietin and anemia. In our study, we investigated the relationship between the severity of interstitial fibrosis (IF) in patients with primary glomerulonephritis (PGN) and anemia parameters. Method A total of 2794 patients who were recorded to the database of the Turkish Society of Nephrology, Glomerular Diseases (TSN-GOLD) Working Group between May 2009 and June 2019 were included in our national multicenter (44 centers) study. Patients aged 16 years or more with documented biopsy were included in the study. Patients were divided into four groups according to IF severity. IF was not detected in the interstitial area, was defined as none, if fibrosis was present in less than 25% of the area, defined as mild, if fibrosis was present in 25-50%, defined as moderate and if more than 50%, defined as severe. Anemia was defined as hemoglobin &amp;lt;12 g/dl in adult female patients and &amp;lt;13 g/dl in adult male patients, according to Clinical Practice Guidelines for anemia of CKD published by The Kidney Disease: Improving Global Outcomes Foundation. The relationship between IF severity and anemia parameters at the time of biopsy was investigated. Results In the study, 57% of the patients were male and their mean age was 41.0 ± 14.3 years. The mean eGFR was 82.7 ± 36.9 ml / min / 1.73 m2 and the hemoglobin level was 13.1 ± 1.9 g/dl. General characteristics of patients with and without anemia are given in Table 1. While 41.1% of patients had no IF, 41.2% had mild, 14.1% had moderate and 3.5% had severe IF. When the patients were divided into four groups according to the severity of IF, the mean hemoglobin and hematocrit levels were significantly different between the groups (Figure 1). Anemia was present in 960 patients (34.4%) (Figure 2). Anemia rate was significantly higher in the patients with IF than patients without IF (36.8% vs 30.9%, p = 0.001). Anemia rate was %25.1 in patients with eGFH≥60 ml/min/1.73m2 and 56% in patients with eGFR&amp;lt;60 ml/min/1.73m2. Gender, serum albumin, eGFR, proteinuria, presence of diabetes, presence of nephrotic syndrome, and presence of IF were the independent variables in the regression analysis of hemoglobin-related factors (Table 2). Conclusion Approximately one-third of PGN patients had anemia at the time of biopsy and the frequency of anemia increases in patients with IF. The presence of IF is an independent risk factor associated with the development of anemia in PGN. The elucidation of the etiopathogenesis of anemia in PGN patients may play an important role in the follow-up and treatment of patients. Studies on IF can play a critical role.

TP0463518, a Novel Prolyl Hydroxylase Inhibitor, Specifically Induces Erythropoietin Production in the Liver.

Prolyl hydroxylase (PHD) 1/2/3 pan inhibitors are known to potentially induce erythropoietin (EPO) production in both the kidney and liver. The 2-[[1-[[6-(4-chlorophenoxy)pyridin-3-yl]methyl]-4-hydroxy-6-oxo-2,3-dihydropyridine-5-carbonyl]amino]acetic acid (TP0463518) is a novel PHD 1/2/3 pan inhibitor; however, the main source of EPO production after TP0463518 administration remained to be investigated. We examined the effect of TP0463518 in inducing EPO production in the kidney and liver by measuring the hypoxia-inducible factor 2α (HIF-2α), EPO mRNA, and serum EPO levels in normal and bilaterally nephrectomized rats. Furthermore, we examined whether liver-derived EPO improved anemia in 5/6 nephrectomized (5/6 Nx) rats. TP0463518 scarcely increased the HIF-2α and EPO mRNA expression levels in the kidney cortex, whereas oral administration of TP0463518 at 40 mg/kg dramatically increased the HIF-2α level from 0.27 to 1.53 fmol/mg and the EPO mRNA expression level by 1300-fold in the livers of healthy rats. After administration of TP0463518 at 20 mg/kg, the total EPO mRNA expression level in the whole liver was 22-fold that in the whole kidney. In bilaterally nephrectomized rats, TP0463518 raised the serum EPO concentration from 0 to 180 pg/ml at 20 mg/kg. Furthermore, repeated administration of TP0463518 at 10 mg/kg increased the reticulocyte count in 5/6 Nx rats on day 7 and raised the hemoglobin level on day 14. The present study revealed that TP0463518 specifically induced EPO production in the liver and improved anemia. The characteristic feature of TP0463518 would lead to not only a more detailed understanding of the PHD-HIF2α-EPO pathway in erythropoiesis, but a new therapeutic alternative for renal anemia. SIGNIFICANCE STATEMENT: Prolyl hydroxylase (PHD) 1/2/3 pan inhibitors are known to potentially induce erythropoietin (EPO) production in both the kidney and liver; however, their effects on renal EPO production have been shown to vary depending on the experimental conditions. The authors found that 2-[[1-[[6-(4-chlorophenoxy)pyridin-3-yl]methyl]-4-hydroxy-6-oxo-2,3-dihydropyridine-5-carbonyl]amino]acetic acid (TP0463518), a PHD 1/2/3 pan inhibitor, specifically induced EPO production in the liver and that the liver-derived EPO was pharmacologically effective. Investigation of the effects of TP0463518 may pave the way for the development of a new therapeutic alternative for renal anemia patients.

Hypoxia-Inducible Factor Activators in Renal Anemia: Current Clinical Experience.

Prolyl hydroxylase domain oxygen sensors are dioxygenases that regulate the activity of hypoxia-inducible factor (HIF), which controls renal and hepatic erythropoietin production and coordinates erythropoiesis with iron metabolism. Small molecule inhibitors of prolyl hydroxylase domain dioxygenases (HIF-PHI [prolyl hydroxylase inhibitor]) stimulate the production of endogenous erythropoietin and improve iron metabolism resulting in efficacious anemia management in patients with CKD. Three oral HIF-PHIs-daprodustat, roxadustat, and vadadustat-have now advanced to global phase III clinical development culminating in the recent licensing of roxadustat for oral anemia therapy in China. Here, we survey current clinical experience with HIF-PHIs, discuss potential therapeutic advantages, and deliberate over safety concerns regarding long-term administration in patients with renal anemia.

Prevalence of anemia in patients with type 2 diabetes

Background Diabetes mellitus (DM) has a high prevalence worldwide. It leads to various complications, including microvascular and macrovascular complications. The nephropathy may undermine the renal production of erythropoietin, positively contributing to an increased anemia framework. The inflammatory situation created by kidney disease also interferes with intestinal iron absorption. Therefore, diabetic patients with kidney disease have higher risk for developing anemia. Aim The aim of this work was to determine the prevalence and various types of anemia in patients with type 2 DM. Patients and methods After obtaining informed written consent, all diabetics as well as control individuals were subjected to detail history, clinical examination, and investigations as follows: fasting blood glucose, postprandial blood glucose, glycated hemoglobin, complete blood count, peripheral smear for type of anemia, reticulocyte count and renal function test, creatinine clearance, urine examination, albuminuria, and stool examination through routine and microscopic fecal occult blood test. Results The prevalence of anemia among our studied patients with type 2 DM was 65%, with significant increase compared with control group (10%). Diabetics had microcytic hypochromic anemia among 55.4%, whereas 44.6% had normocytic normochromic anemia. There was a significant negative correlation between hemoglobin level and degree of albuminuria and a significant positive correlation between hemoglobin level and creatinine clearance. Conclusion Anemia is a common finding in patients with type 2 DM when compared with the general population. Hence in diabetic patients, it would be desirable to evaluate the hemoglobin levels often, even when the renal parameters are within the normal limits, for better quality of life.

Regulation of Red Blood Cell Volume with Exercise Training.

Hypervolemia is a hallmark of endurance training (ET) and manifests by similar elevations in plasma (PV) and red blood cell volume (RBCV) so that hematocrit largely remains unaltered following weeks/months of training. While the mechanisms facilitating PV expansion with ET have been previously reviewed extensively this is not the case for RBCV. Endurance champions may have 40% more RBCV than controls and RBCV may increase up to 10% following months of regular exercise training in healthy individuals. Such adaptations are the main factor leading to concomitant changes in maximal oxygen uptake. The increase in RBCV is preceded by that of PV after few ET sessions, which in turn transiently decreases the hematocrit. The "critmeter" theory suggests that O2 sensors located within the juxtamedullary apparatus regulate the hematocrit via modulation of renal erythropoietin (EPO) production according to arterial O2 content-dependent changes in tissue O2 pressure. Hence, the initial decrease in hematocrit can be considered as a primary mechanism facilitating RBCV expansion with ET. Furthermore, after a single endurance exercise bout blood volume-regulating hormones ANGII and VPN increase transiently. Both stimulate renal EPO production. Catecholamines and cortisol, stress hormones acutely increased by endurance exercise, may facilitate the release of red blood cells from the bone marrow, thus possibly contributing to ET-induced erythropoiesis. These and other endocrine effects could be enhanced by the hyperplasia of the hematopoietic bone marrow observed in endurance athletes. © 2019 American Physiological Society. Compr Physiol 9:149-164, 2019.

Endogenous H2S production deficiencies lead to impaired renal erythropoietin production.

Patients suffering from chronic kidney disease (CKD) experience a number of associated comorbidities, including anemia. Relative deficiency in renal erythropoietin (EPO) production is thought to be a primary cause of anemia. Interestingly, CKD patients display low levels of hydrogen sulfide (H2S), an endogenously derived renal oxygen sensor. Previous in vitro experiments have revealed that H2S-deficient renal cell lines produce less EPO than wild-type renal cell lines during hypoxia. We postulated that H2S might be a primary mediator of EPO synthesis during hypoxia, which was tested using an in vivo murine model of whole-body hypoxia and in clinical samples obtained from CKD patients. Following a 72-hour period of hypoxia (11% O2), partial H2S knockout mice (lacking the H2S biosynthetic enzyme cystathionine γ-lyase [CSE]) displayed lower levels of hemoglobin, EPO and cystathionine-β-synthase (CBS) (another H2S biosynthetic enzyme) compared to wild-type mice, all of which was rescued by exogenous H2S supplementation. We also found that anemic CKD patients requiring exogenous EPO exhibited lower urinary thiosulfate levels compared to non-anemic CKD patients of similar CKD classification. Together, our results confirm an interplay between the actions of H2S during hypoxia and EPO production.

Tubular immaturity causes erythropoietin-deficiency anemia of prematurity in preterm neonates

Kidneys are physiologically hypoxic due to huge oxygen consumption for tubular reabsorption. The physiological hypoxia makes the kidney an appropriate organ for sensitively detecting oxygen levels and producing erythropoietin (EPO). In preterm neonates, immature kidneys cannot produce sufficient EPO, which results in anemia of prematurity (AOP). The cause of EPO insufficiency in AOP has been unclear, therefore current therapeutic options are transfusion and injection of recombinant human EPO. This report shows that the cause of insufficient EPO production in AOP is elevated renal oxygen levels due to poor oxygen consumption by immature tubules. Neonatal mice with AOP showed low tubular transporter expression and elevated renal oxygen levels compared with those without AOP. Enhancing transporter expression in AOP mice induced renal hypoxia and EPO production. In preterm neonates, red blood cell counts, hemoglobin levels, and hematocrit levels correlated with tubular function, but not with serum creatinine, gestational age, or birth weight. Furthermore, pharmacological upregulation of hypoxia signaling ameliorated AOP in mice. These data suggest that tubular maturation with increased oxygen consumption is required for renal EPO production.

Does Renal Tubular Injury–Induced Local Tissue Hypoxia Involve Post-Transplantation Erythrocytosis?

BackgroundThe pathogenesis of post-transplantation erythrocytosis (PTE) is not well understood and appears to be multifactorial. Our hypothesis in this study was that several factors, including toxicity of calcineurin inhibitor, immunologic factors, and chronic allograft nephropathy, can trigger local tissue hypoxia in peritubular interstitium, which is where production of erythropoietin (EPO) takes place. This local interstitial tissue hypoxia can cause an increase in renal EPO production, which induces the development of PTE. MethodsThis cross-sectional study included 15 renal transplant recipients, in whom polycythemia developed after kidney transplantation, with elevated hematocrit level to >51%. Forty-eight age- and gender-matched renal transplant recipients with normal hematocrit level were included as the renal transplant control group. In addition, 13 age- and gender-matched healthy subjects were also included as the healthy control group. We used urine hypoxia-inducible factor-2 alpha (HIF-2α) levels to evaluate whether there is local tissue hypoxia in renal allograft. HIF-2α levels were measured by double antibody sandwich enzyme-linked immunosorbent assay (ELISA). Serum EPO and insulin-like growth factor-1 (IGF-1) levels were also measured. ResultsHIF-2α levels were significantly lower in the polycythemia group than the other two groups, but there was no significant difference between the healthy control group and the renal transplant control group with regard to HIF-2α levels. There was no significant difference among the 3 study groups in terms of levels of serum EPO and IGF-1. ConclusionLocal tissue hypoxia in renal allograft does not seem to play an important role in the development of PTE.