Effect of intravenous vitamin C on cytokine activation and oxidative stress in end-stage renal disease patients receiving intravenous iron sucrose.

Reticuloendothelial blockade in hemodialysis patients prevents optimal intravenous (IV) iron utilization. Vitamin C has emerged as a potential therapy to improve anemia treatment by enhancing iron mobilization. However, Vitamin C can act as a pro-oxidant in the presence of iron. This was a prospective, open-label, crossover study. Thirteen patients with end-stage renal disease on hemodialysis and four healthy controls were assigned to receive 100 mg of IV iron sucrose (IS) or 100 mg of IV IS co-administered with 300 mg of IV Vitamin C (IS + C) in random sequence. Serum samples for IL-1, IL-6, TNF-α and IL-10 and non-transferrin bound iron were obtained at baseline, 45 min and 105 min post study medication administration. Peripheral blood mononuclear cells were isolated at the same time points and stained with fluorescent probes to identify intracellular reactive oxygen species and mitochondrial membrane potential (Δψm) by flow cytometry. Lipid peroxidation was assessed by plasma F2-isoprosatane concentration. Both IS and IS + C were associated with increased plasma F2-isoprostanes concentrations post-infusion. Maximal plasma F2-isoprostane concentrations after IS + C were significantly elevated from baseline (234 ± 0.04 vs. 0.198 ± 0.028 ng/mL, p = 0.02). After IS + C, IL-1, IL-6, IL-10, and TNF-alpha were significantly elevated compared to baseline. After IS alone only IL-6 was noted to be elevated. Intracellular production of H(2)O(2) and loss of mitochondrial membrane potential (Δψm) was observed after IS while IS + C was associated with increased O (2) (·-) production. Both IS and IS + C induced serum cytokine activation accompanied by lipid peroxidation, however, IS + C induced higher plasma concentrations of F2-isoprostanes, IL-1, IL-10, and TNF-α post-infusion. Long-term safety studies of IV iron co-administered with Vitamin C are warranted.

Non-transferrin bound iron, cytokine activation and intracellular reactive oxygen species generation in hemodialysis patients receiving intravenous iron dextran or iron sucrose.

Intravenous (IV) iron supplementation is widely used to support erythropoeisis in hemodialysis patients. IV iron products are associated with oxidative stress that has been measured principally by circulating biomarkers such as products of lipid peroxidation. The pro-oxidant effects of IV iron are presumed to be due at least in part, by free or non-transferrin bound iron (NTBI). However, the effects of IV iron on intracellular redox status and downstream effectors is not known. This prospective, crossover study compared cytokine activation, reactive oxygen species generation and oxidative stress after single IV doses of iron sucrose and iron dextran. This was a prospective, open-label, crossover study. Ten patients with end-stage renal disease (ESRD) on hemodialysis and four age and sex-matched healthy were assigned to receive 100 mg of each IV iron product over 5 min in random sequence with a 2 week washout between products. Subjects were fasted and fed a low iron diet in the General Clinical Research Center at the University of New Mexico. Serum and plasma samples for IL-1, IL-6, TNF-α and IL-10 and NTBI were obtained at baseline, 60 and 240 min after iron infusion. Peripheral blood mononuclear cells (PBMC) were isolated at the same time points and stained with fluorescent probes to identify intracellular reactive oxygen species and mitochondrial membrane potential (Δψm) by flow cytometry. Lipid peroxidation was assessed by plasma F(2) isoprostane concentration. Mean ± SEM maximum serum NTBI values were significantly higher among patients receiving IS compared to ID (2.59 ± 0.31 and 1.0 ± 0.36 µM, respectively, P = 0.005 IS vs. ID) Mean ± SEM NTBI area under the serum concentration-time curve (AUC) was 3-fold higher after IS versus ID (202 ± 53 vs. 74 ± 23 µM*min/l, P = 0.04) in ESRD patients, indicating increased exposure to NTBI. IV iron administration was associated with increased pro-inflammatory cytokines. Serum IL-6 concentrations increased most profoundly, with a 2.6 and 2.1 fold increase from baseline in ESRD patients given IS and ID, respectively (P < 0.05 compared to baseline). In healthy controls, serum IL-6 was undetectable at baseline and after IV iron administration. Most ESRD patients had increased intracellular ROS generation, however, there was no difference between ID and IS. Only one healthy control had increased ROS generation post IV iron. All healthy controls experienced a loss of Δψm (100% with IS and 50% with ID). ESRD patients also had loss of Δψm with a nadir at 240 min. IS administration was associated with higher maximum serum NTBI concentrations compared to ID, however, the both compounds produced similar ROS generation and cytokine activation that was more pronounced among ESRD patients. The effect of IV iron-induced ROS production on pivotal signaling pathways needs to be explored.

Comparison of oxidative stress markers after intravenous administration of iron dextran, sodium ferric gluconate, and iron sucrose in patients undergoing hemodialysis.

STUDY OBJECTIVE: To compare non-transferrin-bound iron and markers of oxidative stress after single intravenous doses of iron dextran, sodium ferric gluconate, and iron sucrose. DESIGN: Prospective, open-label, crossover study. SETTING: University-affiliated general clinical research center. PATIENTS: Twelve ambulatory patients undergoing hemodialysis. INTERVENTION: Patients received 100 mg of intravenous iron dextran, sodium ferric gluconate, and iron sucrose in random sequence, with a 2-week washout period between treatments. MEASUREMENTS AND MAIN RESULTS: Serum samples for transferrin saturation, non-transferrin-bound iron, and malondialdehyde (MDA; marker of lipid peroxidation) were obtained before (baseline) and 30, 60, 120, and 360 minutes and 2 weeks after each iron infusion. A serum sample for hemeoxygenase-1 (HO-1) RNA was obtained at baseline and 360 minutes after infusion. Non-transferrin-bound iron values were significantly higher 30 minutes after administration of sodium ferric gluconate and iron sucrose compared with iron dextran (mean +/- SEM 10.1 +/- 2.2, 3.8 +/- 0.8, and 0.23 +/-0.1 microM, respectively, p<0.001 for sodium ferric gluconate vs iron dextran, p = 0.002 for iron sucrose vs iron dextran). A significant positive correlation was noted between transferrin saturation and the presence of non-transferrin-bound iron for sodium ferric gluconate and iron sucrose (r2 = 0.37 and 0.45, respectively, p<0.001) but not for iron dextran (r2 = 0.09). After sodium ferric gluconate, significantly more samples showed increases in MDA levels from baseline compared with iron sucrose and iron dextran (p = 0.006); these increased levels were associated with the presence of non-transferrin-bound iron, baseline transferrin saturation above 30%, baseline transferrin levels below 180 mg/dl, and ferritin levels above 500 ng/ml (p<0.05). However, only a transferrin level below 180 mg/dl was independently associated (odds ratio 4.8, 95% confidence interval 1.2-15.3). CONCLUSION: Iron sucrose and sodium ferric gluconate were associated with greater non-transferrin-bound iron appearance compared with iron dextran. However, only sodium ferric gluconate showed significant increases in lipid peroxidation. The relationship between non-transferrin-bound iron from intravenous iron and oxidative stress warrants further exploration.

Therapeutic use of the phosphate binder lanthanum carbonate.

Hyperphosphatemia is recognized as a principal mineral disorder in chronic kidney disease (CKD) that leads to the development of secondary hyperparathyroidism. Recent data indicate that hyperphosphatemia is associated with accelerated cardiac calcification and increased mortality in patients with CKD. Control of serum phosphorus is accomplished with phosphate binder therapies that include calcium and aluminum salts. Recently, calcium-based binders have undergone reevaluation because of their association with cardiac calcification. The non-calcium, non-aluminum binder sevelamer hydrochloride has been associated with slower progression of cardiac calcification in clinical trials. Lanthanum carbonate is a newer phosphate binder with phosphate binding activity similar to aluminum salts making this agent a compelling alternative; however, more data are needed to evaluate long-term safety and effects on cardiovascular end points.

Elevated serum creatinine levels associated with fenofibrate therapy.

PURPOSE: The case of a patient who developed clinically relevant increases in serum creatinine (SCr) levels while receiving fenofibrate therapy is reported. SUMMARY: Fenofibrate therapy was initiated for a 60-year old Hispanic man with stage 4 chronic kidney disease (CKD) for the treatment of hypertriglyceridemia. Two weeks after taking 48 mg of fenofibrate daily, the patient's SCr and blood urea nitrogen concentrations increased from 3.0 and 25 mg/dL, respectively, to 3.5 and 30 mg/dL, respectively. His estimated glomerular filtration rate (eGFR) had decreased from 24.8 to 17.9 mL/min/1.73 m(2). One month after initiating fenofibrate, his SCr concentration had increased to 3.7 mg/dL, a 32% increase from baseline. Because of persistently high triglyceride concentrations (e.g., 402 mg/dL), the fenofibrate dosage was increased to 145 mg daily. The patient's SCr concentration rose to 4.7 mg/dL (a 62% increase from baseline), and his eGFR was calculated as 13 mL/min/1.73 m(2). The patient was referred by the nephrology service for vascular-access placement in preparation for hemodialysis. Four days after discontinuation of fenofibrate, the patient's SCr concentration dropped to 3.3 mg/dL and returned to baseline approximately six weeks later, with an eGFR of 20.5 mL/min/1.73 m(2). Preparation for hemodialysis was terminated, and the patient's eGFR remained stable at 20.2 mL/min/1.73 m(2) for the 12 months after fenofibrate discontinuation. A score of 4 on the Naranjo et al. probability scale indicated that there was a possible association between fenofibrate and renal dysfunction in this patient. CONCLUSION: A 60-year-old patient developed renal impairment after receiving fenofibrate for the treatment of hypertriglyceridemia.

Non-transferrin-bound iron is associated with enhanced Staphylococcus aureus growth in hemodialysis patients receiving intravenous iron sucrose.

BACKGROUND: Hemodialysis vascular access infections are most frequently caused by Staphylococcus spp. The purpose of this study was to determine if S. aureus growth is enhanced after administration of IV iron sucrose and to establish a relationship between the appearance of non-transferrin-bound iron (NTBI) and S. aureus growth. METHODS: Serum samples were obtained from 12 hemodialysis patients receiving maintenance doses of 100 mg of iron sucrose at baseline and 5, 30, 90, 220 min and 48 h after iron administration. Assays for NTBI and transferrin saturation were performed. S. aureus isolates were used to inoculate patient serum samples. Bacterial growth was determined by optical density. RESULTS: Six of 12 patients had NTBI present within 30 min of the iron dose. NTBI was present more frequently in patients with baseline transferrin saturation values >30% (p < 0.05). Bacterial growth was significantly greater in patients who had NTBI present at 5, 90 and 220 min after iron administration compared to those who did not have NTBI present. CONCLUSIONS: Doses of 100 mg of iron sucrose are associated with the presence of NTBI and enhanced S. aureus growth.