Bone marrow changes following treatment of renal anemia with erythropoietin

Cardiovascular Consequences of Uremic Metabolites: an Overview of the Involved Signaling Pathways

The crosstalk of the heart with distant organs such as the lung, liver, gut, and kidney has been intensively approached lately. The kidney is involved in (1) the production of systemic relevant products, such as renin, as part of the most essential vasoregulatory system of the human body, and (2) in the clearance of metabolites with systemic and organ effects. Metabolic residue accumulation during kidney dysfunction is known to determine cardiovascular pathologies such as endothelial activation/dysfunction, atherosclerosis, cardiomyocyte apoptosis, cardiac fibrosis, and vascular and valvular calcification, leading to hypertension, arrhythmias, myocardial infarction, and cardiomyopathies. However, this review offers an overview of the uremic metabolites and details their signaling pathways involved in cardiorenal syndrome and the development of heart failure. A holistic view of the metabolites, but more importantly, an exhaustive crosstalk of their known signaling pathways, is important for depicting new therapeutic strategies in the cardiovascular field.

Increased cardiovascular risk in rats with primary renal dysfunction; mediating role for vascular endothelial function

Primary chronic kidney disease is associated with high cardiovascular risk. However, the exact mechanisms behind this cardiorenal interaction remain unclear. We investigated the interaction between heart and kidneys in novel animal model for cardiorenal interaction. Normal Wistar rats and Munich Wistar Fromter rats, spontaneously developing renal dysfunction, were subjected to experimental myocardial infarction to induce cardiac dysfunction (CD) and combined cardiorenal dysfunction (CRD), respectively (N = 5–10). Twelve weeks later, cardiac- and renal parameters were evaluated. Cardiac, but not renal dysfunction was exaggerated in CRD. Accelerated cardiac dysfunction in CRD was indicated by decreased cardiac output (CD 109 ± 10 vs. CRD 79 ± 8 ml/min), diastolic dysfunction (E/e′) (CD 26 ± 2 vs. CRD 50 ± 5) and left ventricular overload (LVEDP CD 10.8 ± 2.8 vs. CRD 21.6 ± 1.7 mmHg). Congestion in CRD was confirmed by increased lung and atrial weights, as well as exaggerated right ventricular hypertrophy. Absence of accelerated renal dysfunction, measured by increased proteinuria, was supported by absence of additional focal glomerulosclerosis or further decline of renal blood flow in CRD. Only advanced peripheral endothelial dysfunction, as found in CRD, appeared to correlate with both renal and cardiac dysfunction parameters. Thus, proteinuric rats with myocardial infarction showed accelerated cardiac but not renal dysfunction. As parameters mimic the cardiorenal syndrome, these rats may provide a clinically relevant model to study increased cardiovascular risk due to renal dysfunction. Peripheral endothelial dysfunction was the only parameter that correlated with both renal and cardiac dysfunction, which may indicate a mediating role in cardiorenal interaction.

Erythropoietin prevents haloperidol treatment-induced neuronal apoptosis through regulation of BDNF

Functional alterations in the neurotrophin, brain-derived neurotrophic factor (BDNF) have recently been implicated in the pathophysiology of schizophrenia. Furthermore, animal studies have indicated that several antipsychotic drugs have time-dependent (and differential) effects on BDNF levels in the brain. For example, our previous studies in rats indicated that chronic treatment with the conventional antipsychotic, haloperidol, was associated with decreases in BDNF (and other neurotrophins) in the brain as well as deficits in cognitive function (an especially important consideration for the therapeutics of schizophrenia). Additional studies indicate that haloperidol has other deleterious effects on the brain (eg increased apoptosis). Despite such limitations, haloperidol remains one of the more commonly prescribed antipsychotic agents worldwide due to its efficacy for the positive symptoms of schizophrenia and its low cost. Interestingly, the hematopoietic hormone, erythropoietin, in its recombinant human form rhEPO has been reported to increase the expression of BDNF in neuronal tissues and to have neuroprotective effects. Such observations provided the impetus for us to investigate in the present study whether co-treatment of rhEPO with haloperidol could sustain the normal levels of BDNF in vivo in rats and in vitro in cortical neuronal cultures and further, whether BDNF could prevent haloperidol-induced apoptosis through the regulation of key apoptotic/antiapoptotic markers. The results indicated that rhEPO prevented the haloperidol-induced reduction in BDNF in both in vivo and in vitro experimental conditions. The sustained levels of BDNF in rats with rhEPO prevented the haloperidol-induced increase in caspase-3 (p<0.05) and decrease in Bcl-xl (p<0.01) protein levels. Similarly, in vitro experiments showed that rhEPO prevented (p<0.001) the haloperidol-induced neuronal cell death as well as the decrease in Bcl-xl levels (p<0.01). These findings may have significant implications for the development of neuroprotective strategies to improve clinical outcomes when antipsychotic drugs are used chronically.

Brain-derived neurotropic factor/TrkB signaling in the pathogenesis and novel pharmacotherapy of schizophrenia

The role of neurotropins, predominantly brain-derived neurotropic factor (BDNF), has been implicated in the pathophysiology as well as treatment outcome of schizophrenia. Both human and rodent studies indicate that the beneficial effects of antipsychotic drugs are mediated, at least in part, through BDNF and its receptor, TrkB. This review will discuss the available data on the levels of BDNF and TrkB in subjects with schizophrenia and in animals with and without conventional antipsychotics. The data concerning the impact of the antipsychotic drugs on BDNF/TrkB signaling will also be discussed. More importantly, this review will provide future perspective on BDNF/TrkB signaling as a novel molecular target to correct the pathogenesis and improve the long-term clinical outcome by treatments with conventional and adjunctive drugs.

Long-term erythropoietin therapy improves response in myelodysplastic syndrome

We report on a 53-year-old Japanese female on hemodialysis with myelodysplastic syndrome whose condition improved with recombinant human erythropoietin (epoetin) therapy. In 1992, based on a diagnosis of folic acid deficiency anemia, folate derivatives were administered. However, the anemia did not improve, and red blood cells had to be transfused subsequently. The transfusion volume was gradually increased afterward, as renal failure progressed, probably due to nephropathy by phenacetin. In 1998, when hemodialysis started, epoetin therapy was started with a dose of 3000 units three times per week. In July 2001, myelodysplastic syndrome (MDS) of a refractory anemia type was diagnosed through bone marrow aspiration. Myelodysplastic syndrome might cause an epoetin-resistant renal anemia. Afterwards the transfusion volume was gradually reduced, and transfusions were not performed after March 2002. Improvements of histological findings of MDS as well as anemia were confirmed by bone marrow aspiration in July 2003. This is an unusual case of a patient with a previously existing MDS, who subsequently develops end stage renal disease, and has an amelioration of her underlying MDS with the administration of epoetin over a long-term period, while being treated with chronic hemodialysis, even when not effective for a short-term.

Neuroprotective effects and intracellular signaling pathways of erythropoietin in a rat model of multiple sclerosis

In multiple sclerosis (MS), long-term disability is primarily caused by axonal and neuronal damage. We demonstrated in a previous study that neuronal apoptosis occurs early during experimental autoimmune encephalomyelitis, a common animal model of MS. In the present study, we show that, in rats suffering from myelin oligodendrocyte glycoprotein (MOG)-induced optic neuritis, systemic application of erythropoietin (Epo) significantly increased survival and function of retinal ganglion cells (RGCs), the neurons that form the axons of the optic nerve. We identified three independent intracellular signaling pathways involved in Epo-induced neuroprotection in vivo: Protein levels of phospho-Akt, phospho-MAPK 1 and 2, and Bcl-2 were increased under Epo application. Using a combined treatment of Epo together with a selective inhibitor of phosphatidylinositol 3-kinase (PI3-K) prevented upregulation of phospho-Akt and consecutive RGC rescue. We conclude that in MOG-EAE the PI3-K/Akt pathway has an important influence on RGC survival under systemic treatment with Epo.

Characteristics and clinical relevance of chronic anemia in adult heart transplant recipients

BACKGROUND

Mild chronic anemia following heart transplantation (HTX), with hemoglobin (Hb) values of 10-14 g/dL in men and 10-12 g/dL in women, is frequent. It has continued to be of uncertain etiology yet clinical relevance. Nonetheless, therapeutic immunosuppression has been regarded as a major cause of chronic anemia in HTX patients.

METHODS

Sixty outpatients were observed over a period of 5 yr after HTX. Laboratory values related to anemia such as Hb, erythropoietin (EPO), ferritin, transferrin, iron, and vitamin levels were obtained and analyzed monthly. Patients were divided into two groups retrospectively. Patients with persistent anemia for more than 1 yr were compared with non-anemic patients.

RESULTS

Forty-three (72%) of the 60 patients were anemic. Anemia was normochromic, normocytic, and slightly anisocytic. Anemic and non-anemic patients showed EPO levels within the expected range as defined by Erslev (Erythropoietin. N Engl J Med 1991: 324: 1339). Reticulocyte counts were found to be normal in all patients. Iron deficiency and deficiency of vitamin B12 or folic acid were not observed. Patients with persistent anemia showed a significantly shorter survival period than non-anemic patients (p<0.02).

CONCLUSIONS

Mild anemia following HTX shows the same characteristics as anemia in chronic diseases. Persisting mild anemia used to be associated with a shorter life expectancy. There is no evidence that standard immunosuppression causes anemia.

Fetal proteins and chronic treatment with low-dose erythropoietin

The potential stimulating effect of erythropoietin on the production of fetal proteins (FPs) has not been explored in human subjects. Therefore, the plasma levels of fetal fibrinogen (FF), carcinoembriogenic antigen (CEA), alpha-fetoprotein (AFP), and fetal hemoglobin (HbF) were measured in 12 uremic hemodialyzed patients before the first administration and after 1, 2, and 3 months of low-dose erythropoietin (r-Hu-EPO; 45 U/kg body wt I.V., thrice weekly). Such a treatment efficaciously increased total hemoglobin (Hb). CEA and AFP increased from 5.8 +/- 1.1 ng/ml and 2.9 +/- 0.9 ng/ml to the final value of 43.2 +/- 3.9 ng/ml and 8.7 +/- 1.1 ng/ml, respectively, in the absence of detectable neoplastic diseases. The levels of FF did not change. HbF levels increased from <3% of Hb to the peak value of 48% at the end of the first month; subsequently, a progressive reduction in HbF was observed. Similar changes were detected in the reticulocyte count (RET). A striking correlation was found between HbF and RET (r = 0.8633, p < 0.0001), indicating that the increment in HbF was dependent on the erythroid activity. In conclusion, this study evidences broader than expected effects of erythropoietin on the synthesis of FP and suggests that (1) r-Hu-EPO markedly increases HbF in a condition of suppressed bone marrow activity, (2) the measurement of the cell proliferation markers CEA and AFP is unreliable during r-Hu-EPO therapy, and (3) the prothrombotic state associated with chronic r-Hu-EPO treatment in patients with uremia cannot be attributed to the presence of FF.

Intrarenal extramedullary erythropoiesis in renal allograft fine-needle aspirates

Recombinant human erythropoietin (rhEPO) is widely used in patients with end-stage renal disease and occasionally in renal allograft recipients to correct anemia. Red blood cell production is markedly increased by rhEPO; however, no extramedullary erythropoiesis (EME) has been associated with this hormone. We observed intrarenal EME in five allograft fine-needle aspirates performed for reduced graft function in four patients between 3.7 and 7 weeks following transplantation. These four patients received rhEPO during dialysis and three resumed rhEPO therapy after transplantation; all four remained anemic. Donors were between 13 months and 13 years of age, with one pediatric and three adult recipients. Aspirates with apparently incidental EME contained all stages of red blood cell precursors, but these cells were not observed in corresponding peripheral blood samples. The hematopoietic cells could be readily distinguished from cells of lymphoid origin. There were no correlations between intragraft EME and aspirate or clinical diagnosis referable to renal dysfunction. Aspirates performed prior to 3.7 weeks or after 7 weeks did not demonstrate EME. These data suggest that endogenous EPO and rhEPO in anemic patients receiving pediatric renal allografts may activate red blood cell precursors in the young graft, inducing intrarenal EME. Recognition of this entity is important to distinguish it from immune activation or malignancy within the donor organ.

The effect of erythropoietin on platelet function in uraemic children on haemodialysis

The effect of 1-year erythropoietin (rHu-EPO) treatment on the bleeding time, platelet aggregation, ATP and thromboxane B2 (TXB2) release, cyclic AMP (cAMP) concentration and platelet surface positive charge were studied in 8 haemodialysed children with chronic uraemia and 8 controls. The pre-dialysis haematocrit (Hct) was 0.21 + 0.01 before and 0.36 + 0.01 following 1 year of rHu-EPO therapy. At the end of this period the pre-dialysis bleeding time became normal (P < 0.05); this was associated with a significant increase in platelet aggregability (P < 0.05), ATP release (P < 0.05) and TXB2 production (P < 0.01), and with a significant decrease in platelet cAMP concentration (P < 0.01). A further increase in platelet aggregation, ATP release and TXB2 production and a decrease in platelet cAMP concentration was observed following bicarbonate haemodialysis (BHD) (P < 0.01). There was a significant positive correlation between platelet aggregation and ATP release (r = 0.78, P < 0.05), as well as platelet aggregation and TXB2 production (r = 0.68, P < 0.05). A significant negative correlation was found between platelet aggregability and cAMP concentration (r = -0.7, P < 0.05). The platelet surface positive charge, which was significantly lower in the patients than in the controls (P < 0.01), did not change during rHu-EPO therapy, nevertheless BHD resulted in a significant increase (P < 0.05), suggesting the surface charge may influence platelet aggregation. In an in vitro and an in vivo study, rHu-EPO and the higher Hct did not increase platelet aggregation directly. Long-term administration of rHu-EPO stimulated complex functional and biochemical changes in the platelets of uraemic patients, which resulted in an improved aggregability.

Erythropoietin in cardiac surgery

Erythropoietin is the primary growth factor for red blood cells. A glycoprotein hormone synthesized by the kidneys, erythropoietin serves to increase red blood cell production in response to tissue hypoxia. It exerts its effect by increasing the numbers of erythroid progenitor cells in the bone marrow, and by increasing the rate at which their development is accomplished. With the introduction of recombinant erythropoietin in 1987, an important pharmacological agent became available for the manipulation of erythropoiesis. While used primarily for the treatment of the anemia of renal failure, recombinant erythropoietin has also shown usefulness in treating other types of anemias in which the endogenous erythropoietin response is insufficient. Perioperative use of the drug grew as a natural extension of this, and erythropoietin has been applied to correct preoperative anemia, augment autologous blood donation, and improve postoperative red cell recovery. Analysis of these perioperative clinical studies reveals success in these areas, but it also reveals that closer attention to the physiology of the natural response, and to the pharmacology of the recombinant product, might significantly improve results. Such an improvement in efficacy is both desirable and necessary when use of the drug is viewed in the setting of today's changing health care environment. By optimizing dosing schedules and targeting the drug to those most at risk for red cell transfusion, recombinant erythropoietin will likely become an important tool in efforts to achieve the elusive goal of bloodless cardiac surgery.

Treatment of anemia in inflammatory bowel disease with recombinant human erythropoietin: results in three patients

Inflammatory bowel disease (IBD) is often associated with anemia. Of 85 patients with IBD, 28 were anemic and had an inadequately low plasma erythropoietin (EPO) concentration. Three patients with a long-standing history of IBD and refractory chronic anemia (hemoglobin values < 10 g/dL, plasma EPO concentrations below 100 mU/mL) were treated with recombinant human EPO, which was administered subcutaneously three times per week at a dose of 200-300 U/kg of body weight. Bone marrow biopsy specimens taken before therapy showed slightly decreased erythropoiesis with a shift of erythroid precursors toward more immature stages. EPO treatment resulted in a marked increase in hemoglobin values in all 3 patients. Bone marrow biopsies after EPO therapy showed quantitatively and qualitatively normal erythropoiesis in all of them. Correction of anemia was followed by improved well-being, and all patients were able to cope much better with their IBD. In all three patients, there was an increase in body weight and their Karnofsky index improved. After a complete workup and exclusion of any other cause for anemia, erythropoietin treatment, although expensive, should be considered in patients with IBD and refractory anemia.