Clinical aspects of iron use in the anemia of kidney disease.
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Publications and source records attributed to Walter H Hörl.
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Iron deficiency is the most common cause of hyporesponsiveness to erythropoiesis-stimulating agents (ESAs) in end-stage renal disease (ESRD) patients. Iron deficiency can easily be corrected by intravenous iron administration, which is more effective than oral iron supplementation, at least in adult patients with chronic kidney disease (CKD). Iron status can be monitored by different parameters such as ferritin, transferrin saturation, percentage of hypochromic red blood cells, and/or the reticulocyte hemoglobin content, but an increased erythropoietic response to iron supplementation is the most widely accepted reference standard of iron-deficient erythropoiesis. Parenteral iron therapy is not without acute and chronic adverse events. While provocative animal and in vitro studies suggest induction of inflammation, oxidative stress, and kidney damage by available parenteral iron preparations, several recent clinical studies showed the opposite effects as long as intravenous iron was adequately dosed. Thus, within the recommended international guidelines, parenteral iron administration is safe. Intravenous iron therapy should be withheld during acute infection but not during inflammation. The integration of ESA and intravenous iron therapy into anemia management allowed attainment of target hemoglobin values in the majority of pediatric and adult CKD and ESRD patients.
A stable supramolecular cluster in T cells at the contact site of APCs, the immunological synapse (IS), is essential for full T cell activation. Failure of IS maturation, as determined by defective relocalization of the TCR/CD3 complex at the T cell/APC contact site, is linked with T cell hyporesponsiveness. The effects of clinically used immunosuppressants on these critical events, however, are undefined. Here, we show that treatment of T cells with cyclosporin A, FK506, and dexamethasone, which are known to inhibit calcineurin and NF-kappaB, respectively, but not rapamycin, the inhibitor of mammalian target of rapamycin, selectively prevented TCR/CD3 relocalization into the IS, while relocalization of adhesion and cytoskeletal proteins as well as T cell/APC conjugate formation remained unaltered. The involvement of calcineurin and NF-kappaB in IS maturation was confirmed by using specific inhibitors of these molecules (FR901725, gossypol, SN50). FK778, as an inhibitor of DNA replication and also TCR/CD3-activated tyrosine kinases, globally abrogated cytoskeletal, adhesion, and signaling molecule relocalization, thereby preventing formation of an IS at an earlier, immature stage along with impaired, antigen-specific T cell/APC conjugate formation. Collectively, blocking IS formation at distinct stages may mediate effects on T cell activation of currently used immunosuppressants, apart from their capacity to block gene transcription, cytokine signaling, and DNA replication. Furthermore, these data imply novel functions of calcineurin and NF-kappaB for successful IS maturation.
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Dendritic cells (DC) are the most potent antigen-presenting cells (APC) and are pivotal for initiating allograft immunity. Recently, particular DC subsets have been implicated also in allogeneic T cell hyporesponsiveness. Alemtuzumab (anti-CD52, Campath-1H) is a novel T cell depleting antibody that is currently under investigation for the use in allogeneic organ transplantation. While recent studies demonstrated a conspicuous effect of alemtuzumab on peripheral DC in clinical graft-versus-host disease, its efficiency in patients receiving allogeneic organ transplants is still undefined. In the present study we assessed the peripheral DC repertoire in kidney transplant recipients after either alemtuzumab induction therapy followed by FK506 monotherapy or after conventional immunosuppression (FK506, mycophenolate mofetil and steroids) without any induction agent. Induction with alemtuzumab caused a strong and sustained reduction of the total number of peripheral DC and a significant shift from myeloid to plasmacytoid DC subsets (mDC/pDC ratio) as early as 1 month post-transplantation. These data show that alemtuzumab induction targets the peripheral DC repertoire, which might add another mechanism allowing immunosuppressive drug minimization. Further studies are warranted to further elucidate the functional significance of these finding in the setting of allogeneic organ transplantation.
BACKGROUND: Lower concentrations of endothelial progenitor cells (EPCs) may be associated with increased cardiovascular risk. EPC counts and their correlates have not yet been studied in kidney transplant recipients (KTR). METHODS: We cross-sectionally studied EPC counts in 105 middle-aged KTR (mean estimated glomerular filtration rate 45.2 ml/min/1.73 m; range: 5.4 to 117.5). Using univariate and multivariate linear regression assuming a gamma distribution of the outcome, we examined the associations between counts of cultured EPCs and traditional cardiovascular disease risk factors (hypertension, diabetes, hyperlipidemia, smoking), kidney function, and immunosuppressive agents, amongst others. RESULTS: The median count of cultured EPCs was 34 cells per high-power field (interquartile range: 19 to 64), comparable to healthy individuals. From multivariate analyses, we found independent inverse associations between counts of cultured EPCs and body mass index, mean arterial pressure, and history of cardiovascular disease. Statin use was associated with greater EPC counts, whereas patients receiving azathioprine or angiotensin II receptor treatment had lower EPC counts (all P<0.01). CONCLUSIONS: This study suggests negative associations in KTR between EPC counts and body mass index, and blood pressure, whereas statin use was associated with greater EPC counts. These findings raise the hypothesis whether EPCs are responsible, at least in part, for the well established associations between these factors and cardiovascular outcomes in KTR.
BACKGROUND: Humoral alloresponses may contribute to chronic allograft nephropathy (CAN) in a subset of kidney transplant recipients. For chronic humoral rejection, the efficacy of rescue therapy with tacrolimus and mycophenolate mofetil has been suggested. METHODS: Eleven recipients with C4d-positive CAN (index biopsy performed after a median of 3 years posttransplantation), who had been on cyclosporine A-based immunosuppression, were converted to tacrolimus, and if not part of basal therapy, to mycophenolate mofetil. We evaluated the effect of this tacrolimus/mycophenolate mofetil rescue therapy on clinical outcomes and on alloantibody formation detected with flow cytometric testing of panel-reactive antibody. RESULTS: Tacrolimus/mycophenolate mofetil rescue therapy (plus anti-rejection treatment in six recipients with additional signs of acute cellular rejection) failed to prevent progressive deterioration of graft function. Four patients returned to dialysis after 4 to 18 months. Serial post-transplant serology detected HLA class I and/or II reactivity in seven recipients. Tacrolimus/mycophenolate mofetil therapy did not affect the time course of alloantibody levels. One patient with C4d-positive transplant glomerulopathy, who did not respond to tacrolimus/mycophenolate mofetil rescue therapy, developed nephrotic-range proteinuria associated with a rapid decline of allograft function. Despite considerable reduction in alloantibody levels and nearly complete clearance of C4d deposits, immunoadsorption failed to prevent graft failure in this patient. CONCLUSION: Our data argue against the efficacy of tacrolimus/mycophenolate mofetil rescue therapy in established C4d-positive chronic allograft dysfunction. Prospective trials are needed to evaluate whether early initiation of this or other antihumoral strategies are capable of effectively preventing alloantibody-mediated chronic graft injury.
Bleeding diathesis and thrombotic tendencies are characteristic findings in patients with end-stage renal disease. The pathogenesis of uremic bleeding tendency is related to multiple dysfunctions of the platelets. The platelet numbers may be reduced slightly, while platelet turnover is increased. The reduced adhesion of platelets to the vascular subendothelial wall is due to reduction of GPIb and altered conformational changes of GPIIb/IIIa receptors. Alterations of platelet adhesion and aggregation are caused by uremic toxins, increased platelet production of NO, PGI(2), calcium and cAMP as well as renal anemia. Correction of uremic bleeding is caused by treatment of renal anemia with recombinant human erythropoietin or darbepoetin alpha, adequate dialysis, desmopressin, cryoprecipitate, tranexamic acid, or conjugated estrogens. Thrombotic complications in uremia are caused by increased platelet aggregation and hypercoagulability. Erythrocyte-platelet-aggregates, leukocyte-platelet-aggregates and platelet microparticles are found in higher percentage in uremic patients as compared to healthy individuals. The increased expression of platelet phosphatidylserine initiates phagocytosis and coagulation. Therapy with antiplatelet drugs does not reduce vascular access thrombosis but increases bleeding complications in endstage renal disease patients. Heparin-induced thrombocytopenia (HIT type II) may develop in 0-12 % of hemodialysis patients. HIT antibody positive uremic patients mostly develop only mild thrombocytopenia and only very few thrombotic complications. Substitution of heparin by hirudin, danaparoid or regional citrate anticoagulation should be decided based on each single case.
BACKGROUND: Hyperlipidemia is highly prevalent in kidney transplant recipients, but the prognostic significance for mortality and allograft survival in these patients has not been established sufficiently. METHODS: We prospectively enrolled 733 kidney transplant recipients between 1996 and 1998. Clinical information was collected and blood was drawn for laboratory evaluation. Information on the previous transplantation procedures and organ donor were obtained from the Eurotransplant Foundation database. We used the Austrian Dialysis and Transplantation Registry for follow-up. Using multivariate proportional hazard regression, independent relations of fasting plasma triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels to risk for death from any cause and risk for kidney allograft loss were examined. RESULTS: During a median follow-up of 6.1 years, 154 patients died and 260 kidney allografts were lost. After careful multivariate adjustment, there were no significant associations between TG and TC levels and patient mortality. Patients in the highest quartile of TG and TC levels had no difference in risks for mortality compared with patients in the lowest quartile of these parameters (hazards ratio, 0.81; 95% confidence interval, 0.51 to 1.28; hazards ratio, 0.68; 95% confidence interval, 0.42 to 1.10, respectively). Similarly, no associations were found with allograft loss. Further analysis of associations between high-density lipoprotein cholesterol or low-density lipoprotein cholesterol categories and patient mortality or kidney allograft loss did not show associations. CONCLUSION: Elevated levels of TC or its subfractions and elevated TG levels are not associated with increased risk for patient mortality or allograft loss in these kidney transplant recipients.
BACKGROUND: This study is designed to assess the effect of early and complete correction of anemia by using recombinant human erythropoietin (epoetin) alfa on the progression of chronic kidney disease (CKD). METHODS: Patients were randomly assigned to achieve high (13 to 15 g/dL [130 to 150 g/L]) or low (11 to 12 g/dL [110 to 120 g/L]) hemoglobin-level targets during 4 months of stabilization, followed by 36 months of maintenance. Glomerular filtration rate (GFR) decrease was measured by using iohexol clearance. Quality of life, nutrition, and safety also were monitored. RESULTS: Because of labeling changes for subcutaneous administration of epoetin alfa (Eprex; Johnson and Johnson, Schaffhausen, Switzerland), the study was terminated prematurely. There were 195 patients enrolled in each group; 108 high-hemoglobin and 133 low-hemoglobin patients entered the maintenance phase. Mean maintenance duration was 7.4 months for the high-hemoglobin group and 8.3 months for the low-hemoglobin group. GFR decrease was numerically, but not statistically significantly, lower with the high-hemoglobin group (0.058 versus 0.081 mL/min/1.73 m2/mo [< 0.01 mL/s/1.73 m2/mo]). Physical quality-of-life measures showed trends (Role-Physical, P = 0.055; Physical Function, P = 0.083) or statistically significant improvement (Vitality, P = 0.042) with high hemoglobin levels at the end of the stabilization phase. Adverse events were similar between groups. Cardiovascular adverse events occurred in 25% of the high-hemoglobin and 18% of the low-hemoglobin patients (P = 0.137). Neither epoetin dosage nor hemoglobin level was associated with cardiovascular adverse events or death. CONCLUSION: These data suggest that normalization of hemoglobin levels in patients with CKD is safe. Longer duration studies are needed to clarify efficacy benefits with high hemoglobin levels.
BACKGROUND: FK778, a derivative of the active leflunomide-metabolite, A77 1726, has been shown to be a powerful immunosuppressant in several transplantation models, particularly efficient in the prevention of chronic allograft rejection. However, the cellular and molecular mechanisms underlying these effects of FK778 have not been investigated yet in detail. Because dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) and are essential for the initiation of immune responses including acute and chronic allograft rejection, we investigated whether FK778 affects this particular cell type. METHODS: Allogeneic T cell stimulation by FK778-treated human monocyte-derived DCs was determined by mixed leukocyte cultures. Surface molecule expression was analyzed by flow-cytometric analysis and cytokine production by ELISA from culture supernatants. Activation of NF-kappaB in DCs was assessed by electrophoretic mobility shift assays. RESULTS: Treatment of DCs with FK778 inhibited their potency to stimulate allogeneic T cells. In line, LPS- and CD40L-induced upregulation of DC surface activation markers and production of IL-12 was significantly inhibited, irrespective of whether cells were treated during or after the monocyte to DC differentiation period. The effects of FK778 on DCs were not reversible by exogenous uridine indicating that FK778 acts independently of its action as an inhibitor of pyrimidine synthesis. On the signaling level, activation of NF-kappaB, the essential transcription factor involved in DC maturation and function, was markedly inhibited by FK778. CONCLUSIONS: Inhibition of activation and function of DCs as the central APCs may significantly contribute to the immunosuppressive profile of FK778 when applied after allogeneic organ transplantation.
BACKGROUND: The Eurotransplant Senior Program (ESP) was launched in 1999, targeted to increase the supply of donor kidneys to the elderly. This program requires local allocation of kidneys from cadaveric donors >>65 years to recipients >>65 years. METHODS: Of all patients >>65 years who received a kidney transplant in 1999-2002 at our center, 59 patients were transplanted through the ESP protocol (ESP group), and 44 patients received a transplant from a younger donor (EuroTransplant Kidney Allocation System, ETKAS group). Recipients were followed for up to 5.3 years using the Austrian Dialysis and Transplant Registry. Outcomes studied included all-cause mortality and allograft loss. RESULTS: Age, sex, and comorbid conditions did not differ by group. Donor age was higher (69 vs. 36 years; P < 0.001) and cold ischemia time shorter in the ESP group (10 vs. 15 hr; P < 0.001). Number of HLA mismatches was greater in the ESP group (3.8 vs. 3.0; P = 0.003). ESP patients were more likely to receive induction therapy and less likely to receive cyclosporine A. Primary nonfunction, delayed graft function, operative mortality, rate of acute rejection episodes, and length of stay did not differ by group. Although serum creatinine at discharge was higher in ESP patients (1.7 vs. 1.4 mg/dL; P < 0.001), 4-year mortality (hazard ratio [HR] = 0.68; 95% CI: 0.31-1.49) and graft loss (HR = 0.61; 95% CI: 0.29-1.28) tended to be less. CONCLUSIONS: Long-term patient and graft survival were comparable between elderly patients who received their organ via the ESP and the regular ETKAS algorithm.
BACKGROUND: Residual renal function is an independent predictor of survival in peritoneal dialysis patients. Systemic administration of radio contrast media (CM) may increase the risk of acute renal failure in patients with impaired renal function not on dialysis. There are few data on the influence of CM administration in dialysis patients. METHODS: We investigated residual renal function in 10 continuous ambulatory peritoneal dialysis (CAPD) patients who underwent elective diagnostic intravenous or intra-arterial administration of CM (study group). Iopromide (a iodinated, non-ionic hypo-osmolar CM) was used for all interventions. The median dose of CM given was 107.5 ml/patient. Residual renal function (calculated as the average of renal creatinine and renal urea clearance) was measured on the day before the intervention (baseline), on days 1-7, day 10 and day 30 after intervention. Eight CAPD patients without exposure to CM acted as the control group. RESULTS: There was no significant difference between the two groups in age, gender, diabetes, duration of dialysis and renal clearance at baseline. In the study group, we observed a temporary decline of residual renal clearance after administration of CM (P<0.05; Friedman test). On day 30, clearances were not significantly different from baseline. In the control group, there was no significant change of residual clearance during the observation period. Repeated measures ANOVA revealed no significant difference in the course of residual renal function between study and control groups. The decline of residual renal clearance between baseline and a routine visit after 4 months was comparable between groups. CONCLUSION: Administration of iopromide did not lead to a persistent decline of residual renal function in CAPD patients. Nevertheless, non-ionic hypo-osmolar CM should be given to these patients with the lowest possible dose and only if there is a real clinical indication.
Vascular dysfunction in chronic renal failure may be linked to reduced nitric oxide (NO) bioactivity and increased circulating concentrations of the endogenous NO synthase inhibitor asymmetrical dimethyl L-arginine (ADMA). The association between ADMA and basal endothelial NO release and endothelium-dependent vasodilation in resistance arteries of chronic renal failure patients is unknown. Forearm blood flow responses to the endothelium-dependent vasodilator acetylcholine, the endothelium-independent vasodilator nitroglycerine, and the endothelium-dependent vasoconstrictor N(G)-monomethyl-L-arginine (L-NMMA) were assessed in 37 peritoneal dialysis patients. L-arginine and ADMA plasma concentrations were measured by HPLC. ADMA (mean +/- SEM: 0.68 +/- 0.02 micromol/L) was associated with basal forearm blood flow (r = -0.33; P < 0.05) and L-NMMA induced vasoconstriction (r = -0.55; P < 0.0005), but not with dilator effects of acetylcholine or nitroglycerine. L-arginine (68 +/- 3 micromol/L) tended to correlate with acetylcholine-induced vasodilation (r = 0.32; P = 0.05) but was not associated with other parameters. ADMA is related to basal but not to acetylcholine-stimulated NO bioactivity in patients on peritoneal dialysis. Impaired endothelium-dependent vasodilation found in chronic renal failure is not explained by elevated circulating NO synthase inhibitors in renal failure.
Hemodialysis patients are prone to deficiency of vitamin C, which constitutes the most abundant nonenzymatic antioxidant in blood. Because antioxidants are involved in the pathogenesis of atherosclerosis, the authors examined the association of total vitamin C plasma level with cardiovascular outcomes in such patients. One hundred thirty-eight consecutive maintenance hemodialysis patients (median age 61 yr, 90 males) were enrolled in a single-center study. At baseline, routine laboratory parameters were recorded, and predialysis total vitamin C plasma levels were measured by high-pressure liquid chromatography. Patients were prospectively followed-up for the occurrence of a primary composite endpoint consisting of fatal and nonfatal major adverse cardiovascular events (MACE) and for all-cause and cardiovascular mortality. MACE occurred in 35 patients (25%) over a period of median 30 mo, and 42 patients (30%) died [29 cardiovascular deaths (21% of total)]. Using Cox proportional hazards modeling, adjusted hazard ratios for the occurrence of MACE were 3.90 (95% confidence interval [CI]: 1.42 to 10.67; P = 0.008) and 3.03 (95% CI: 1.03 to 8.92; P = 0.044) for patients in the lower (<32 micromol/L) and middle (32 to 60 micromol/L) tertile of total vitamin C levels, compared with patients in the upper tertile (>60 micromol/L). Hazard ratios for cardiovascular death were 3.79 (95% CI: 1.23 to 11.66; P = 0.020) and 2.89 (95% CI: 0.89 to 9.37; P = 0.076). Total vitamin C levels were not independently associated with all-cause mortality. This study concludes that low total vitamin C plasma levels predict adverse cardiovascular outcomes among maintenance hemodialysis patients. Future studies should address the potential protective effect of an adequate vitamin C supplementation.
Leflunomide, a potent disease-modifying antirheumatic drug used in the treatment of rheumatoid arthritis (RA), exhibits anti-inflammatory, antiproliferative and immunosuppressive effects. Although most of the beneficial effects of leflunomide have been attributed to its antimetabolite activity, mainly in T cells, other targets accounting for its potency might still exist. Because of mounting evidence for a prominent role of dendritic cells (DCs) in the initiation and maintenance of the immune response in RA, we analyzed the effect of the active metabolite of leflunomide (A77 1726; LEF-M) on phenotype and function of human myleloid DCs at several stages in their life cycle. Importantly, DCs differentiated in the presence of LEF-M exhibited an altered phenotype, with largely reduced surface expression of the critical co-stimulatory molecules CD40 and CD80. Furthermore, treatment of DCs during the differentiation or maturation phase with LEF-M aborted successful DC maturation. Exogenous addition of uridine revealed that DC modulation by LEF-M was independent of its proposed ability as an antimetabolite. In addition, the ability of DCs to initiate T-cell proliferation and to produce the proinflammatory cytokines IL-12 and tumour necrosis factor-alpha was markedly impaired by LEF-M treatment. As a molecular mechanism, transactivation of nuclear factor-kappaB, an transcription factor essential for proper DC function, was completely suppressed in DCs treated with LEF-M. These data indicate that interference with several aspects of DC function could significantly contribute to the beneficial effects of leflunomide in inflammatory diseases, including RA.
OBJECTIVE: Leflunomide, a potent disease-modifying antirheumatic drug of the isoxazole class, exhibits antiinflammatory, antiproliferative, and immunosuppressive effects by largely unknown mechanisms, although alterations of pyrimidine synthesis have been proposed. Successful immune responsiveness requires T cell activation by interaction with antigen-presenting cells (APCs), and integrin activation and formation of an immunologic synapse (IS). In this study, we evaluated the impact of the active leflunomide metabolite teriflunomide on T cell integrin activation, evolution of the IS, and antigen-specific formation of stable T cell/APC conjugates. METHODS: Effects of pharmacologic concentrations of teriflunomide on CD3/CD28- and lymphocyte function-associated antigen 1-induced signal transduction and activation of primary human T cells were investigated. Furthermore, T cells were stimulated with superantigen- and antigen-pulsed APCs to study relocalization of molecules to the IS and T cell/APC conjugate formation. RESULTS: Teriflunomide inhibited T cell receptor (TCR)/CD3-mediated calcium mobilization, but other critical T cell signaling events, including activation of MAPK and NF-kappaB, remained unaltered. In contrast, inhibition of TCR/CD3-triggered beta1,2 integrin avidity and integrin-mediated costimulation (outside-in signaling) by teriflunomide revealed a striking interference with integrin function that was independent of altered pyrimidine synthesis. Moreover, teriflunomide abolished molecule relocalization to the IS and induction of T cell/APC conjugates. CONCLUSION: These data show that the active metabolite of leflunomide prevents the interaction of T cells with APCs to form an IS. Since IS formation is crucial for eliciting an immune response, this novel mechanism could underlie the beneficial effects of leflunomide in immune-mediated disorders such as rheumatoid arthritis.
Tumor lysis syndrome is a typical oncological complication, characterized by hyperuricemia, hyperkalemia, hyperphosphatemia with secondary hypocalcemia, acidosis and acute renal failure. it occurs particularly in patients with lymphoproliferative diseases during therapy with potent myelosuppressive substances. patients with solid tumors rarely develop a tumor lysis syndrome during anti-neoplastic therapy (chemo-, hormonal-, steroid therapy, radiotherapy). host-related (e.g. pre-existing volume depletion, hyperuricemia, acidic urine) and tumor-related (e.g. large tumor burden, tumor sensitivity to therapy, advanced stage) risk factors contribute markedly to the development of tumor lysis syndrome. prophylaxis and treatment of tumor lysis syndrome consist of adequate hydration of the patients (3 l fluid/m2/day) in order to maintain urine production of > or =100 ml/h, controlled alkalinisation (urine pH 7.0-7.5) and, if necessary, extracorporeal therapy (intermittent or continuous hemodialysis or hemodiafiltration). recombinant urate oxidase (rasburicase) reduces uric acid values by far more effectively than allopurinol. treatment with rasburicase (01.-0.2 mg/kg for 1-7 days) does not only markedly reduce the incidence of tumor lysis syndrome in patients with malignancy but also morbidity and mortality. hyperphosphate-induced acute renal failure due to intrarenal calcium phosphate precipitation may, however, occur even during rasburicase therapy