Hypererythropoietinemia is associated with common diseases like non-uremic anaemia where infection burden is high. Erythropoietin (EPO) is also given as therapy for anaemia associated with chronic kidney disease and cancer and in those who are at a higher risk of infections. EPO is known to have an effect on macrophages by which it helps in the growth of some intracellular pathogens. However, its direct role on bacterial growth is currently unknown.

Here, we investigated the direct effect of recombinant human erythropoietin (rhuEPO) on the growth of pathogenic Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. In silico experiments were designed to gain insight into the mechanisms. We found that 30 IU/L rhuEPO promoted the growth of E. coli and S. aureus and inhibited the growth of P. aeruginosa. In silico observations suggest that bacterial cell surface proteins may interact with the EPO and may cause the observed effects.

It appears that some pathogens can explore EPO to proliferate and growth of others are inhibited by the same. The consequence of such observation is a matter of widespread concern for future research.

Blockers of the renin-angiotensin-aldosterone system (RAAS), such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are routinely used in patients with chronic kidney disease because of their cardiovascular (CV) and renoprotective effects. However, there are no uniform recommendations about RAAS blockers for CV protection in the end-stage renal disease (ESRD) population other than the preferred drug class for blood pressure control. This uncertainty stems from the fact that patients with ESRD were generally excluded from randomized controlled trials evaluating the cardioprotective benefits of RAAS blockers. It is important to weigh the potential harms associated with the use of RAAS blockers, such as electrolyte disturbances and worsening anemia, with their role in protection of residual kidney function, alleviation of thirst and potential CV benefits. The objective of this review is to summarize the current knowledge about the use of RAAS blockers in patients with ESRD.

Anemia is a common complication of chronic kidney disease. Although mechanisms involved in the pathogenesis of renal anemia include chronic inflammation, iron deficiency, and shortened half-life of erythrocytes, the primary cause is deficiency of erythropoietin (EPO). Serum EPO levels in patients with chronic kidney disease are usually within the normal range and thus fail to show an appropriate increase with decreasing hemoglobin levels, as found in nonrenal anemias. Studies elucidating the regulation of EPO expression led to the identification of the hypoxia inducible factor-hypoxia responsive element system. However, despite much progress in understanding the molecular mechanisms through which cells can sense oxygen availability and translate this information into altered gene expression, the reason why EPO production is inappropriately low in diseased kidneys remains incompletely understood. Both alterations in the function of EPO-producing cells and perturbations of the oxygen-sensing mechanism in the kidney may contribute. As with other anemias, the consequences of renal anemia are a moderate decrease in tissue oxygen tensions and counterregulatory mechanisms that maintain total oxygen consumption, including a persistent increase in cardiac output.

The pathogenesis of anemia in patients with chronic renal failure has been greatly attributed to erythropoietin (EPO) deficiency. Recently, however, there has been some thought that uremic inhibitors might suppress the activity of EPO and reduce the maturation of erythropoiesis. Polyamines are well known to be involved in the regulation of cellular proliferation and differentiation. Furthermore, the polyamine levels in the serum or erythrocytes are elevated in chronic hemodialysis patients, and can be lowered immediately by hemodialysis. In the present study, we first measured the polyamines levels (putrescine, spermidine, spermine) by high performance liquid chromatography (HPLC) in 20 chronic hemodialysis patients, and investigated the effects of polyamines on erythropoiesis by in vitro bioassay using fetal mouse liver cells. The direct effects of polyamines in erythroid colony formation in the medium with and without EPO were evaluated. Each polyamine level in chronic hemodialysis patients was higher than in the healthy subjects, and a significant negative correlation was found between polyamines and erythropoiesis. Polyamines inhibited the activity of EPO, but they did not have any direct effect on colony formation of the fetal mouse liver cells. These results suggest that polyamines have inhibitory effects on the proliferation or maturation of erythroid precursor cells and are intimately involved in the pathogenesis of renal anemia in chronic hemodialysis patients.

Quantitative or qualitative abnormalities of erythroid progenitors in patients with chronic renal failure (CRF) could be the major factor for recombinant human erythropoietin (rHuEPO) hyporesponsiveness and severe anemia in hemodialysis (HD) patients receiving rHuEPO therapy.

Purified 1 x 10(4) circulating CD34+ cells isolated from rHuEPO-hyporesponsive HD patients (EPO-H; n = 10), rHuEPO-responsive non-HD patients with CRF (EPO-R; n = 8), nonanemic HD patients without rHuEPO therapy (EPO-W/O; n = 10), and healthy volunteer controls (CON; n = 10) were subjected to a methylcellulose culture system supplemented with rHuEPO, recombinant human interleukin-3 (IL-3), recombinant human stem cell factor (SCF), and recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) for 14 days.

The average number of burst-forming units of erythroids (BFU-Es) was significantly less in the EPO-H group compared with the CON and EPO-W/O groups. Furthermore, colony size also was significantly smaller in the EPO-H group. Total RNAs were extracted from approximately 100 colonies/patient and subjected to complementary DNA expression array studies of 268 growth factors, cytokines, chemokines, and their receptors. A characteristic cluster upregulated in the EPO-R and EPO-W/O groups and downregulated in the EPO-H group was identified that contained various cytokines and growth factors, including IL-6, GM-CSF, vascular endothelial growth factor B, IL-9, IL-3, leukemia inhibitory factor, and interferon alpha-2, and such receptors as thrombopoietin receptor, IL-9 receptor, and colony-stimulating factor 1 receptor.

These data suggest that the cross-talk network or autocrine/paracrine regulatory loop is critically impaired in BFU-E-derived cells in EPO-H patients, and investigation of these cluster genes would facilitate the development of novel therapeutic strategies for such patients.

The impact of dialysis intensity on erythropoietin (EPO) requirements is unclear. Previous work suggests that increased dialysis is associated with increased erythropoietin responsiveness (ERSP), but average dialysis intensity has increased since those publications. We hypothesized that ERSP would be independent of delivered Kt/V(urea) at current intensities of hemodialysis. We prospectively studied 135 stable chronic hemodialysis patients who receive iron and subcutaneous EPO dosed according to current guidelines. We collected biochemical, hematologic, and single pool urea kinetics data. ERSP was expressed as units per kilogram per week of EPO administered. Simple and multiple linear regression were used to identify characteristics predictive of ERSP. The mean age of the patients was 62 +/- 17 years (range, 17-90 years); 68 of 135 (50.3%) were women, and 120 of 135 (88.9%) were Caucasian. Mean delivered Kt/V(urea) was 1.60 +/- 0.49, with 102 of 135 (75.6%) of patients with a delivered Kt/V(urea) > 1.3. Univariate linear regression showed seven significant independent predictors of erythropoietin requirements. Low serum albumin (p < 0.001), low serum calcium (p = 0.002), high serum phosphate (p = 0.004), and high serum iPTH (p = 0.007) were all associated with lower levels of ERSP. Lower ERSP was also correlated with lower hemoglobin and lower serum iron and transferrin saturation. Delivered dialysis (Kt/ V(urea)) was not a significant predictor of ERSP (p = 0.61). Multivariate regression confirmed low serum albumin (p < 0.01), high serum phosphate (p = 0.001), high immunoreactive parathyroid hormone (p = 0.025), and low transferrin saturation (p < 0.0005) as predictors of low ERSP, and also found high serum ferritin to be correlated with low ERSP (p = 0.016). We found no relationship between erythropoietin responsiveness and intensity of hemodialysis in this population of patients with a mean delivered Kt/V(urea) of 1.6. This may indicate a threshold effect beyond which more dialysis will not improve ERSP. However, markers of an underlying inflammatory state and of secondary hyperparathyroidism were associated with decreased response to erythropoietin.

Current guidelines suggest that anaemia due to erythropoietin deficiency almost exclusively occurs with creatinine concentrations of at least 177 micromol/l or above. The aim of this prospective case control pilot study was to evaluate whether borderline renal function or mild renal dysfunction with creatinine concentrations well below 177 micromol/l is sufficient to induce inadequate erythropoietin secretion. Patients referred for work-up of otherwise unexplained anaemia with mildly abnormal creatinine concentrations (104-129 micromol/l; study group: eight patients) and patients referred for work-up or therapy of other diseases who also presented with anaemia but normal creatinine levels (<100 micromol/l; control group: nine patients matched for gender, age and degree of anaemia) were included. All but two patients in the control group had bone marrow biopsies to exclude other pathologies. Mild renal dysfunction (as evidenced by creatinine concentrations between 100 and 140 micromol/l, median concentration 112 micromol/l) was found to be sufficient to induce inadequate erythropoietin secretion. The physiologic hemoglobin-dependent erythropoietin regulation demonstrated in the control group was abolished in the study group. Patients with mild renal dysfunction and unexplained anaemia should be investigated for erythropoietin concentration. If the erythropoietin concentration is found to be inadequate for the degree of anaemia, substitution therapy should be considered.

Physiological parameters such as pH and oxygen tension probably play significant roles in the regulation of haemopoiesis in the bone marrow microenvironment, but these roles have yet to be characterized in detail. We have found that changes in culture pH (0.2 units) can cause significant changes in the culture composition of mature cells and colony-forming cells (CFCs), especially in the presence of erythropoietin (Epo). Peripheral blood (PB) CD34+ cells cultured at different pH values (7.15-7.6) were characterized using total cell counts, colony assays, morphological analysis. haemoglobin staining, flow cytometry, immunocytochemical staining, and Western blots. Cultures performed at high (7.6) pH contained greater numbers of haemoglobin-positive and band-3-positive cells. and acquired these erythroid differentiation markers sooner than standard (7.35) and low (7.1) pH cultures. Flow cytometry using CD71 and CD45RA antigens also indicated that erythroid differentiation proceeds faster at high pH and is blocked at an intermediate stage by low pH. Morphological data confirmed that high pH cultures had been shifted towards late-stage erythroid compartments as compared to low and standard pH cultures. These findings have important implications both in elucidating the regulatory role of pH in the bone marrow microenvironment and for the design of in vitro systems to study the development of erythroid cells.

The hemoglobin concentration and the hematocrit percentage are usually used to diagnose anemias and erythrocytoses and to monitor their treatment and progress. However, they may be misleading because of dehydration or dilution and it is imperative to keep in mind their relationship to the size of the red-cell mass. This size is determined by the cellular kinetics of four distinct compartments which make up the erythron: the stem cells, the progenitor cells, the precursor cells and the mature cells. Under normal physiologic conditions, the kinetics of the progenitor-cell compartment determines the size of the red-cell mass but, under abnormal conditions, the kinetics of each of the compartments may affect the size. In this review, normal and abnormal kinetics of the four compartments are defined and related to the size of the red-cell mass and the pathogenesis of anemias and erythrocytoses.

The purpose of this study was to evaluate the sensitivity and specificity of laboratory methods in the diagnosis of posterythropoietin-era, iron-deficient, chronic renal failure patients. The patient population comprised 25 anemic (hemoglobin < 11 g/dL) patients with creatinine greater than 3 mg/dL; 20 were dialysis patients, two were transplant patients, and three patients had renal failure from other causes. Criteria for study inclusion were as follows: bone marrow iron was the reference standard and was graded 0 to +4, ranging from absent to diffuse homogeneous iron staining; serum ferritin concentration and serum transferrin saturation were tested in terms of sensitivity and specificity. The reference standard indicated that iron deficiency existed in 40% of patients. Neither serum ferritin nor transferrin saturation were completely adequate diagnostic tools. Serum ferritin levels less than 200 ng/dL were 100% specific for the diagnosis but only 41% sensitive. Transferrin saturation of less than 20% was 88% sensitive, but only 63% specific. By excluding patients with hypoproteinemia (transferrin values of < 150 mg/dL), the sensitivity of the test increased to 100% and the specificity to 80%. We conclude that transferrin saturation is an adequate screening tool in anemic chronic renal failure patients, provided that hypoproteinemia is not present. By determining both the serum ferritin concentration and the transferrin saturation, a high sensitivity and specificity can be achieved, even in patients with hypoproteinemia. Furthermore, we believe that on this basis, iron therapy in patients with renal insufficiency can be improved.

The effect of recombinant human erythropoietin (rhEPO) and interleukin 3 (IL3) on circulating haematopoietic progenitors consisting mainly of immature burst-forming-units-erythrocytes (BFU-E), was investigated in ten paediatric patients treated by regular haemodialysis. During a 30-week study rhEPO treatment resulted in a rise of median haemoglobin levels from 6.7 g/dl to > 10 g/dl in all patients. Before initiating rhEPO treatment the number of circulating BFU-E in chronic renal failure patients responded to grading doses of rhEPO in vitro similar to that in control children; however, the dose-response curves were not predictive for the in vivo response to rhEPO. After an initial rise in five patients BFU-E numbers declined by week 30 of rhEPO treatment. BFU-E numbers decreased to 35% of pretreatment values. The number of granulocyte-macrophage colony forming cells (GM-CFC) also decreased during rhEPO treatment. Addition of IL3 to the culture medium containing saturating concentrations of granulocyte-macrophage colony stimulating factor did not stimulate BFU-E numbers of patients before rhEPO treatment or those of controls. However, 2 weeks after start of rhEPO treatment IL3 increased the growth of patient's BFU-E in vitro to 220% of pretreatment levels, followed by a gradual decrease of stimulation until the end of observation. These findings indicate that: (1) long-term recruitment of circulating haematopoietic progenitors during rhEPO treatment is low in children with renal anaemia; (2) rhEPO sensitivity of circulating BFU-E is not predictive for the in vivo response; (3) rhEPO treatment results in enhanced sensitivity of BFU-E to IL3.

Anemia in patients with chronic renal failure (CRF) is multifactorial, and while the majority will respond to the paternal administration of recombinant human erythropoietin (r-HuEPO), a role for coexistent plasma inhibitors and stimulators, such as burst-promoting activity (BPA), remains controversial. To evaluate the latter possibility, eight individuals with CRF on long-term hemodialysis, were studied before (mean hemoglobin 58.4 +/- 8.0 g/l and after 12 weeks of r-HuEPO therapy (mean hemoglobin 100.4 +/- 18.3 g/l). In vitro erythroid cultures using erythroid burst forming unit (BFU-E) and erythroid colony forming unit (CFU-E) assays were performed, plating 5 x 10(4) bone marrow mononuclear cells and comparing growth in heat-inactivated autologous serum with AB serum. Using Step III sheep erythropoietin (Connaught Laboratories, Willowdale, Ontario, Canada) (n = 4), mean BFU-E pre-therapy were 89.7 +/- 75.1, CFU-E were 418.5 +/- 150.6, whereas the corresponding figures in AB serum were 2.5 +/- 2.9 and 197 +/- 94.19, p = 0.1, p = 0.01, respectively. Similarly, with r-HuEPO (EPOCONN: Connaught Laboratories, Willowdale, Ontario, Canada) (n = 4), mean BFU-E were 145.25 +/- 103.3 in autologous serum and 31.0 +/- 56.75 in AB serum (p = 0.04). As controls, erythroid progenitors from two normal donors yielded 69 and 61 BFU-E colonies in autologous serum and 103 and 42 in AB serum; the corresponding CFU-E were 52 and 235 versus 136 and 137.(ABSTRACT TRUNCATED AT 250 WORDS)

The erythropoietic response to graded doses of recombinant human erythropoietin (epoetin alfa) was assessed in 24 hemodialysis patients by quantitative ferrokinetic studies, and measurement of the reticulocyte count and plasma levels of transferrin receptor protein. These responses were compared to those of 22 normal subjects. Epoetin alfa was given intravenously at 15, 50 or 150 U/kg every other day for four injections. Three patients with chronic renal failure were restudied after renal function was restored following renal transplantation. The results of these three different measurements of erythroid function showed that the acute response to recombinant human erythropoietin was similar in normal subjects and patients with renal failure. We conclude that chronic uremia does not alter the responsiveness to erythropoietin in vivo.

In 14 severely anemic patients with end-stage renal disease and chronic hemodialysis the effect of recombinant human erythropoietin (EPO) on hemopoiesis was investigated. Bone marrow biopsies were taken before and after four and 26 months of treatment with EPO to evaluate quantitative and qualitative changes of histomorphology. EPO induced normalization of maturation and an increase in cell mass of the erythropoietic line in all patients. The number of megakaryocyte also increased significantly with EPO treatment (P less than 0.01). At the time of the third bone marrow biopsy (26 months) erythropoiesis was normal. Megakaryopoiesis remained unchanged compared to the second biopsy (4 months). No cytomorphologic abnormalities or other evidence for malignant disorder could be detected in any of the patients. Hematocrit increased from a mean of 19 to 31 percent at the second evaluation (P less than 0.001). Platelet count had risen by a mean of 30,000 at four months (P less than 0.05) and slightly decreased at 26 months. These observations suggest great safety of long-term treatment with recombinant human erythropoietin, and demonstrate efficacy in correcting reduced and immature erythropoiesis in chronically hemodialyzed patients. EPO also stimulates human megakaryopoiesis.

A 38 year old female patient died following massive hemoptysis occurring during maintenance hemodialysis for chronic renal failure. In addition to renal dysfunction, laboratory data showed low levels of serum immunoglobulins; chest X-rays did not reveal any abnormal shadows. For the last 11 months, the patient had not received deferoxamine. At autopsy, major bronchi were plugged with coagulated blood. Irregular thickening of the right main bronchial wall close to the lung hilus was noted. Light microscopic examination disclosed mycotic granulomata in the bronchial wall, where the pulmonary arterial wall was also involved. Immunostaining using specific antibody identified Mucor hyphae. The mucormycosis is a serious complication of chronic renal failure and hemodialysis. In the current case, it is likely that immune dysfunction rather than deferoxamine was the important predisposing factor to the growth of the fungus.

We measured serum erythropoietin levels serially in 31 renal-transplant recipients treated with cyclosporine, using the recently developed recombinant human erythropoietin-based radioimmunoassay. The mean (+/- SEM) serum erythropoietin concentration in these patients before transplantation (14 +/- 2 U per liter) was similar to that in normal subjects who did not have anemia. A transient postoperative 9-fold increase (range, 0- to 74-fold) in the serum erythropoietin levels was followed by a smaller (3-fold) and sustained (28 +/- 3 days) second elevation. The initial increase occurred in the absence of graft function and was not accompanied by an erythropoietic response, whereas the second increase was associated with graft recovery and the complete resolution of the anemia. Serum erythropoietin levels returned to normal as the hematocrit rose above 0.32. Thereafter, the hematocrit continued to rise toward normal, while the serum erythropoietin levels remained normal. The patients in whom erythrocytosis or iron-deficiency anemia developed had persistently elevated serum erythropoietin levels. We conclude that in patients who have undergone renal transplantation, slight increases in endogenous erythropoietin levels induce erythropoiesis to the same extent as do large doses of exogenous erythropoietin in patients with uremia. Moreover, once initiated, erythropoiesis in renal-transplant recipients may be sustained by normal serum erythropoietin levels. These results suggest that the restoration of renal function improves the erythropoietic response to erythropoietin.

To examine the effects of erythropoietin on the anemia of chronic renal disease and on the rate of renal deterioration, we administered recombinant human erythropoietin to 17 patients with anemia and progressive renal failure who did not yet require dialysis (serum creatinine level, 353 to 972 mumol per liter [4.0 to 11.0 mg per deciliter]). The dose of erythropoietin (50 to 150 units per kilogram of body weight) was adjusted according to the hematocrit response. In all 17 patients the anemia responded to erythropoietin. The median hematocrit increased from 0.27 to 0.37. The rate of the response depended on the initial erythropoietin dose and was similar to that observed in patients who were on dialysis. Hypertension was present in 14 patients before therapy, developed during therapy in 2 of the normotensive patients, and worsened in 9 patients, who required additional antihypertensive medications. The rate of the decline in renal function, as measured by serial determination of the reciprocal of the serum creatinine level, did not change significantly as the hematocrit rose (P = 0.78 by the paired t-test) during erythropoietin therapy. All the patients reported improvements in appetite, activity level, and sense of well-being. We conclude that erythropoietin therapy is effective in correcting the anemia of patients with progressive renal failure without affecting renal function, although it may be associated with an increase in blood pressure.

Erythroid progenitors were assayed in 20 chronic hemodialysis patients before and after administration of recombinant human erythropoietin (rhEpo) using a methylcellulose culture method. Hemoglobin concentrations, hematocrit values and the proportion of marrow erythroblasts increased significantly during rhEpo treatment. The numbers of erythroid progenitors (CFU-e and BFU-e) in the patients' marrow also increased following rhEpo administration. Our data suggest that rhEpo is an effective drug for treating anemia caused by chronic renal failure and the administration of rhEpo results in an increase in the numbers of erythroid progenitors.