Iron therapy, advanced oxidation protein products, and carotid artery intima-media thickness in end-stage renal disease

Biochemical and spectrophotometric significance of advanced oxidized protein products

We previously described the presence of advanced oxidation protein products (AOPP), a novel marker of oxidative stress in the plasma of hemodialyzed patients (HD). The present study was carried out to further investigate how myeloperoxidase (MPO)-catalyzed reactions could contribute to AOPP generation in the plasma. First, patterns of plasma protein oxidation obtained after in vitro incubation of control plasma with hypochlorous acid (HOCl) were compared to those from HD patients and control plasma. The use of various analytical techniques enabled localising and identifying the main oxidized proteins with albumin (HSA) after protein separation by size-exclusion chromatography and SDS-PAGE electrophoresis. The characterization of the oxidation level of the individual plasma proteins in terms of carbonyl groups and 3-nitrotyrosine formations was performed by immunoblotting. Secondly, to highlight the significance of AOPP index monitored by spectrophotometry, spectra were established for plasma fractions from HD patients and compared to data for control plasma and HOCl-treated plasma. The corresponding absorbance difference spectra were matched with external standards such as dityrosine, nitrotyrosine and pentosidine and elaborated chromophoric probe models. Indeed, HSA was chlorinated by HOCl reagent or HOCl generated via the MPO/H(2)O(2)/Cl(-) system and was nitrated by tetranitromethane. Increased absorbances at the range of 340 nm were observed both with chlorinated and nitrated HSA. Finally, our results indicate that HOCl, and not NO(2)(*), generated via MPO activity, could represent one of the pathways for AOPP production in plasma proteins exposed to activated phagocytes.

Parenteral iron nephrotoxicity: Potential mechanisms and consequences1

BACKGROUND

Parenteral iron administration is a mainstay of anemia management in renal disease patients. However, concerns of potential iron toxicity persist. Thus, this study was conducted to more fully gauge iron toxicologic profiles and potential determinants thereof.

METHODS

Isolated mouse proximal tubule segments (PTS) or cultured proximal tubular [human kidney (HK-2)] cells were exposed to four representative iron preparations [iron sucrose (FeS), iron dextran (FeD), iron gluconate (FeG), or iron oligosaccharide (FeOS)] over a broad dosage range (0, 30 to 1000 microg iron/mL). Cell injury was assessed by lactate deyhdrogenase (LDH) release, adenosine triphosphate (ATP) reductions, cell cytochrome c efflux, and/or electron microscopy. In vivo toxicity (after 2 mg intravenous iron injections) was assessed by plasma/renal/cardiac lipid peroxidation [malondialdehyde (MDA)], renal ferritin (protein)/heme oxygenase-1 (HO-1) (mRNA) expression, electron microscopy, or postiron injection PTS susceptibility to attack.

RESULTS

In each test, iron evoked in vitro toxicity, but up to 30x differences in severity (e.g., ATP declines) were observed (FeS > FeG > FeD = FeOS). The in vitro differences paralleled degrees of cell (HK-2) iron uptake. In vivo correlates of iron toxicity included variable increases in renal MDA, ferritin, and HO-1 mRNA levels. Again, these changes appeared to parallel in vivo (glomerular) iron uptake (seen with FeS and FeG, but not with FeD or FeOS). Iron also effected in vivo alterations in proximal tubule cell homeostasis, as reflected by the "downstream" emergence of tubule resistance to in vitro oxidant attack.

CONCLUSION

Parenteral iron formulations have potent, but highly variable, cytotoxic potentials which appear to parallel degrees of cell iron uptake (FeS > FeG >> FeD or FeOS). That in vitro injury can be expressed at clinically relevant iron concentrations, and that in vivo glomerular iron deposition/injury may result, suggest caution is warranted if these agents are to be administered to patients with active renal disease.

Association between serum ferritin and measures of inflammation, nutrition and iron in haemodialysis patients

BACKGROUND

Serum ferritin is a frequently used marker of iron status in dialysis patients. Iron administration is to be withheld for ferritin values >800 ng/ml according to K/DOQI guidelines. We hypothesized that such non-iron-related factors as elements of the malnutrition-inflammation complex syndrome (MICS) may increase serum ferritin concentration independently of iron status.

METHODS

We studied 82 prevalent maintenance haemodialysis (MHD) patients (including 43 men), aged 55.7 +/- 15.3 years. The inflammatory and nutritional status was evaluated by serum C-reactive protein (CRP), Subjective Global Assessment (SGA) and its newer, fully quantitative versions, i.e. Dialysis Malnutrition Score (DMS) and Malnutrition-Inflammation Score (MIS).

RESULTS

All but six patients had been on maintenance doses of intravenous iron dextran (between 100 and 200 mg/month) during the 10 weeks prior to the measurements. Serum ferritin levels were increased across SGA categories: (ANOVA P-value 0.03). Both unadjusted and multivariate adjusted correlation coefficients (r) for serum ferritin and CRP vs pertinent values were statistically significant for DMS and MIS and some other measures of nutritional status and iron indices. After deleting 10 MHD patients with either iron deficiency (ferritin <200 ng/ml) or iron overload (ferritin >2000 ng/ml), in the remaining 72 MHD patients both bivariate and multivariate correlations were much stronger and statistically significant (r = -0.33 and -0.29, respectively, P < 0.01). A multivariate model showed simultaneous, significant correlations between serum ferritin and both markers of inflammation and iron status independent of each other. After dividing the 72 MHD patients into two groups of serum ferritin based on a K/DOQI recommended serum ferritin cut-off of 800 ng/ml, the MIS and logarithm of serum CRP were significantly higher in the higher ferritin group.

CONCLUSIONS

Serum ferritin values in the range of 200-2000 ng/ml may be increased due to non-iron-related factors including elements of MICS.

Oxidative stress and renal injury with intravenous iron in patients with chronic kidney disease

BACKGROUND

Intravenous iron is widely prescribed in patients with chronic kidney disease (CKD) and can cause oxidative stress. The relationship of oxidative stress and renal injury in patients with CKD is unknown. Whether renal injury can occur at a time point when transferrin is incompletely saturated is also unclear.

METHODS

We conducted a randomized, open-label, parallel group trial to compare the oxidative stress induced by intravenous administration of 100 mg iron sucrose over 5 minutes and its protection with N-acetylcysteine (NAC) in 20 subjects with stage 3 or 4 CKD. Transferrin saturation was measured with urea polyacrylamide gel electrophoresis, oxidative stress by malondialdehyde (MDA) measurement by high-performance liquid chromatography, and renal injury by enzymuria and proteinuria. Reduced and oxidized glutathione and free radical scavengers as well as urinary monocyte chemoattractant protein-1 were also measured.

RESULTS

Parenteral iron increased plasma concentration and urinary excretion rate of MDA, a biomarker of lipid peroxidation, within 15 to 30 minutes of iron sucrose administration. This was accompanied by enzymuria and increase in proteinuria. In contrast, saturation of transferrin was not maximally seen until 3 hours after the end of infusion. Oxidative stress, enzymuria and proteinuria were transient and were completely resolved in 24 hours. NAC reduced acute generation of systemic oxidative stress but failed to abrogate proteinuria or enzymuria.

CONCLUSION

Intravenous iron produces oxidative stress that is associated with transient proteinuria and tubular damage. The rapid production of oxidative stress even when transferrin is not completely saturation suggests free iron independent mechanism(s) to be operative in producing oxidative stress and transient renal injury. Long-term implications of these findings need further study.

The effects of iron dextran on the oxidative stress in cardiovascular tissues of rats with chronic renal failure

BACKGROUND

Redox-active iron can promote oxidative stress and tissue injury by catalyzing hydroxyl radical generation and lipid peroxidation. Intravenous iron preparations are routinely administered in conjunction with erythropoietin to treat anemia in patients with chronic renal failure (CRF), a condition that is marked by oxidative stress and inflammation. This treatment frequently elevates iron burden, which can potentially intensify oxidative stress and, thus, cardiovascular disease in this population.

METHODS

We studied renal function and oxidative stress parameters in the cardiovascular tissues of CRF (5/6 nephrectomized) and sham-operated control rats 3 months after a single intravenous infusion of iron dextran (500 mg/kg).

RESULTS

Arterial pressure was equally elevated and creatinine clearance was equally reduced in both iron-treated and -untreated CRF groups. Iron administration significantly raised the blood hemoglobin, serum iron concentration, and transferrin saturation in both CRF and control groups. Iron administration resulted in a significant rise in plasma concentration of lipid peroxidation product, malondialdehyde in the CRF rats, and an insignificant rise in the control group. Plasma oxidized low-density lipoprotein (LDL) concentration was increased in the CRF groups, and was not affected by iron administrations. Iron administration raised nitrotyrosine abundance in the aorta of CRF but not in the control group. Left ventricular tissue abundance of p22(phox) subunit of NAD(P)H oxidase was elevated in CRF group and was not affected, whereas p67(phox) subunit abundance was raised by prior iron administration. Iron administration insignificantly lowered aorta p22(phox), but had no effect on p67(phox) subunit abundance in the treated CRF group. Previous iron administration significantly lowered superoxide dismutase and catalase abundance in the aorta and glutathione peroxidase in the left ventricle of CRF animals, but did not significantly change these parameters in the iron-treated control animals.

CONCLUSION

A single intravenous injection of iron dextran increased oxidative stress in the cardiovascular tissues in the CRF group, but not the control rats, pointing to heightened susceptibility to iron-mediated toxicity in CRF. However, administration of iron dextran did not adversely affect kidney function, and favorably affected hemoglobin concentration in rats with CRF induced by renal mass reduction. Further studies are needed to explore the effects of other parenteral iron preparations, repeated intravenous iron administration, and presence of comorbid conditions such as diabetes.

Malnutrition-inflammation complex syndrome in dialysis patients: causes and consequences

Protein-energy malnutrition (PEM) and inflammation are common and usually concurrent in maintenance dialysis patients. Many factors that appear to lead to these 2 conditions overlap, as do assessment tools and such criteria for detecting them as hypoalbuminemia. Both these conditions are related to poor dialysis outcome. Low appetite and a hypercatabolic state are among common features. PEM in dialysis patients has been suggested to be secondary to inflammation; however, the evidence is not conclusive, and an equicausal status or even opposite causal direction is possible. Hence, malnutrition-inflammation complex syndrome (MICS) is an appropriate term. Possible causes of MICS include comorbid illnesses, oxidative and carbonyl stress, nutrient loss through dialysis, anorexia and low nutrient intake, uremic toxins, decreased clearance of inflammatory cytokines, volume overload, and dialysis-related factors. MICS is believed to be the main cause of erythropoietin hyporesponsiveness, high rate of cardiovascular atherosclerotic disease, decreased quality of life, and increased mortality and hospitalization in dialysis patients. Because MICS leads to a low body mass index, hypocholesterolemia, hypocreatininemia, and hypohomocysteinemia, a "reverse epidemiology" of cardiovascular risks can occur in dialysis patients. Therefore, obesity, hypercholesterolemia, and increased blood levels of creatinine and homocysteine appear to be protective and paradoxically associated with a better outcome. There is no consensus about how to determine the degree of severity of MICS or how to manage it. Several diagnostic tools and treatment modalities are discussed. Successful management of MICS may ameliorate the cardiovascular epidemic and poor outcome in dialysis patients. Clinical trials focusing on MICS and its possible causes and consequences are urgently required to improve poor clinical outcome in dialysis patients.

A low serum iron level is a predictor of poor outcome in hemodialysis patients

BACKGROUND

Iron administration has been implicated as a cause of poor clinical outcome in maintenance hemodialysis (MHD) patients. However, the role of low iron levels in the clinical outcome of MHD patients is not clear.

METHODS

We examined the predicting value of baseline serum iron level on prospective mortality and hospitalization in a cohort of all 1,283 MHD patients from 10 DaVita dialysis facilities in Los Angeles County, CA.

RESULTS

Patients aged 57.8 +/- 15.2 years included 49% men, 45% Hispanics, 25% African Americans, and 53% patients with diabetes. During the first 3 months of the cohort, 97% of patients were administered erythropoietin (EPO) and 60% were administered intravenous iron (gluconate and/or dextran) at least once. During a 12-month follow-up, mortality was significantly greater (23%) in the lowest serum iron quartile (<45.3 microg/dL [<8.1 micromol/L]) compared with other quartiles (10% to 12%). Multivariate Poisson and Cox models adjusted for demographic features, dialysis dose and vintage, serum albumin and ferritin and blood hemoglobin concentrations, and administered EPO and iron doses showed that both serum iron level and iron saturation ratio had significant, but inverse, associations with prospective mortality and hospitalization. There was a statistically significant trend toward greater rates of mortality and hospitalization with lower serum iron levels. This reverse association remained significant in a subcohort of 322 MHD patients after additional adjustments for comorbid conditions and serum C-reactive protein level to reflect inflammation.

CONCLUSION

Low baseline serum iron indicators are associated with increased mortality and hospitalization in MHD patients independent of hemoglobin level, EPO and iron doses, indicators of nutrition and inflammation, and comorbid conditions. Clinical trials to examine the role of iron administration in improving morbidity and mortality by increasing serum iron levels in MHD patients are required.

Glycoxidation and inflammation in renal failure patients

BACKGROUND

Inflammation is common in patients with chronic renal failure and has been associated with the increased risk for cardiovascular disease (CVD) in this condition. Advanced glycoxidation end products (AGEs) are among the factors implicated in the inflammatory state of chronic renal failure.

METHODS

In a cross-sectional study of 189 dialysis patients, we measured circulating levels of C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), vascular adhesion molecule-1 (VCAM-1), vascular endothelial growth factor (VEGF), and plasminogen activator inhibitor-1 (PAI-1) to test for possible relationships between them and serum AGE levels. In addition, these parameters were measured in a subgroup of 18 patients with chronic renal failure randomly assigned to a 4-week diet, either low (L-AGE) or high (H-AGE) in AGE content. AGEs were measured by means of a monoclonal antibody against epsilonN-carboxymethyllysine.

RESULTS

At baseline, serum AGE levels, as well as those for CRP, TNF-alpha, VCAM-1, and VEGF, were markedly elevated, although no correlation was found between AGE levels and the other markers. Dietary AGE modulation resulted in a significant decrease in levels of serum AGEs, CRP, and PAI-1 in the L-AGE group (approximately 35%, 44%, and 17%, respectively; P < 0.03), whereas only serum AGE levels increased significantly in the H-AGE group. VCAM-1 and TNF-alpha levels, although similar at baseline, became significantly lower in patients on an L-AGE compared with H-AGE diet (P < 0.05) at the end of the study.

CONCLUSION

Data from the interventional phase of the study suggest that AGEs have a role in the initiation of the inflammatory state of chronic renal failure, which eventually leads to increased CVD. This finding opens the possibility for using anti-AGE strategies in the prevention and treatment of CVD in patients with chronic renal failure.

Phospholipid plasmalogen, a surrogate marker of oxidative stress, is associated with increased cardiovascular mortality in patients on renal replacement therapy

BACKGROUND

There is a high incidence of premature cardiovascular disease (CVD) in patients with end-stage renal disease (ESRD). Free radical-induced tissue damage is thought to play a major role in the pathogenesis of atherosclerosis, and there are several reports indicating an increased oxidative stress in ESRD. However, it is not well established that increased oxidative stress predicts cardiovascular mortality in ESRD. Plasmalogens, a group of phospholipids with a vinyl ether bond in the sn-1 position, are considered to be sensitive markers of oxidative stress.

METHODS

Cardiovascular and non-cardiovascular mortality was recorded (follow-up time 1860+/-94 days) in 105 ESRD patients (mean age 51+/-2 years) in whom the fasting ratio of the erythrocyte levels of plasmalogens (DMA 16/C16:0 and DMA 18/C18:0) had been determined at the start of renal replacement therapy (RRT). The prevalence of malnutrition (subjective global assessment), diabetes mellitus (DM), smoking habits and CVD was also determined.

RESULTS

Thirty-eight patients who died of CVD (0.066+/-0.003) had a significantly lower DMA 16/C16:0 ratio than 15 patients who died of non-cardiovascular causes (0.078+/-0.005; P<0.05) and 52 patients alive at follow-up (0.075+/-0.003; P<0.05). A Cox proportional hazard model analysis showed that a low (<median) DMA 16/C16:0 ratio at the start of RRT was associated (relative risk 1.50; confidence interval 1.07-2.16; P<0.05) with CVD mortality independently of age, gender, DM and CVD.

CONCLUSION

These results suggest that increased oxidative stress may be a risk factor for cardiovascular mortality in ESRD.

Effects of LDL apheresis and vitamin E-modified membrane on carotid atherosclerosis in hemodialyzed patients with arteriosclerosis obliterans

BACKGROUND

Hemodialysis patients manifest accelerated atherosclerosis. Hemodialysis is associated with oxidative stress, which can be partially prevented with the use of a vitamin E-coated dialyzer. Adsorption of low-density lipoprotein (LDL) has been applied in the treatment of arteriosclerosis obliterans (ASO). The aim of the present study was to determine whether the vitamin E-coated dialyzer and/or LDL apheresis affects carotid atherosclerosis in hemodialysis patients with ASO.

METHODS

Thirty hemodialysis patients with ASO were divided into four treatment groups: treatment with conventional cellulose or synthetic membranes (group A, n = 12), treatment with vitamin E-coated membrane (group B, n = 7), treatment with conventional membrane and LDL apheresis (group C, n = 6), and treatment with vitamin E-coated membrane and LDL apheresis (group D, n = 5). Carotid artery intima-media thickness (IMT) and arterial stiffness assessed by pulse wave velocity (PWV), plasma C-reactive protein (CRP) and interleukin (IL)-6 were measured before and 10 weeks after treatment and compared between groups. All values were referred to measurements after LDL apheresis.

RESULTS

IMT and PWV, plasma CRP and IL-6 showed little change in group A throughout the experimental period. These decreased slightly from the baseline value in group B, but the change was not significant. In group C, IMT decreased from 1.12 +/- 0.24 to 1.02 +/- 0.18 mm (p < 0.05), and PWV decreased from 2,266 +/- 380 to 1,968 +/- 342 cm/s (p < 0.05). Plasma CRP and IL-6 concentrations also decreased significantly compared with baseline (p < 0.05). In group D, IMT decreased from 1.18 +/- 0.26 to 0.92 +/- 0.18 mm (p < 0.01), and PWV decreased from 2,284 +/- 390 to 1,786 +/- 284 cm/s (p < 0.01). Plasma CRP and IL-6 levels also decreased significantly compared with baseline (p < 0.01).

CONCLUSION

These data suggest that LDL apheresis and the vitamin E-coated membrane dialysis in combination may prevent further progression of atherosclerosis in hemodialysis patients with ASO.

Low-dose continuous iron therapy leads to a positive iron balance and decreased serum transferrin levels in chronic haemodialysis patients

BACKGROUND

Iron balance is critical for adequate erythropoiesis, but its optimal therapeutic regimen remains to be defined. Continuous maintenance therapy with iron has been proposed for dialysis patients on recombinant human erythropoietin (rHuEpo) in the hope that the regimen is adequate and safe.

METHODS

We determined serum ferritin, transferrin, transferrin saturation (TSAT), serum transferrin receptors, albumin and C-reactive protein (CRP) in a 3-year prospective study in 30 chronic haemodialysis patients on dialysis treatment for 132+/-111 months (18 males, 12 females; mean age 56+/-14 years). Beginning in the year 2000, they regularly received low-dose maintenance iron supplementation (i.v. iron gluconate 31.25 mg/week) for 12 months (Period 1 or first treatment phase), followed by a 6-month withdrawal (Period 2 or stop phase) and then by continuous maintenance iron therapy (i.v. iron gluconate 31.25 mg/week) for another 9 months (Period 3 or re-challenge phase).

RESULTS

A significant increase in serum ferritin and TSAT was observed, with values exceeding 500 ng/ml and 50% in 10/30 (33%) and 7/30 (23%) of subjects, respectively, in Period 1, and in 11 and 5% in Period 3. A significant decrease in serum transferrin was documented during Period 1, followed by an increase in Period 2 and a decrease in Period 3. Serum albumin remained stable. Serum transferrin was always negatively correlated with ferritin (r = -0.41, P<0.001) and weakly correlated with serum transferrin receptors (r = 0.178, P<0.05), but was not correlated with serum albumin or CRP. Regression equations based on pre-treatment serum ferritin values were developed for predicting the value of serum ferritin at any time following the beginning of continuous iron supplementation. They fitted a linear relationship for males (y = 81 + 21.5 x time) and for females (y = 65 + 22 x time). Percentile charts for quantitative tracking of serum ferritin increases and decreases in patients have also been developed from values measured at different times. These charts show box-plot distributions of expected ferritin against time.

CONCLUSIONS

Even continuous low-dose maintenance iron therapy, with only 31.25 mg weekly over 1 year, cannot prevent the risk of iron overload in patients with moderate anaemia. Furthermore, this treatment is responsible for decreases in serum transferrin, unrelated to changes in serum albumin, possibly of concern for hypo-transferrinaemia as an independent risk factor for iron toxicity.

Association Between High Serum Ferritin Levels and Carotid Atherosclerosis in the Study of Health in Pomerania (SHIP)

BACKGROUND AND PURPOSE

Several studies have provided evidence for a relationship between body iron load and cardiovascular disease. We analyzed the association of serum ferritin levels with carotid atherosclerosis.

METHODS

We assessed intima-media thickness and plaque prevalence in the carotid arteries by high-resolution ultrasound among 2443 participants (1200 women; age, 45 to 79 years) in the Study of Health in Pomerania (SHIP), a population-based study in northeast Germany.

RESULTS

In multivariate analysis, serum ferritin levels were not independently associated with carotid intima-media thickness among women or men. In contrast, the relationship between serum ferritin levels and carotid plaque prevalence was significant among men (odds ratio per 1-SD increase of serum ferritin levels, 1.33; 95% confidence interval, 1.08 to 1.44) yet not among women (odds ratio, 1.29; 95% confidence interval, 0.98 to 1.75). However, both men and women showed a dose-response relation between serum ferritin levels and carotid atherosclerosis in which higher serum ferritin levels were associated with greater odds ratios for carotid plaque prevalence. Additionally, there was an interaction of serum ferritin levels with low-density lipoprotein (LDL) cholesterol (P=0.039) among men in which the association of serum ferritin levels with carotid plaque prevalence became stronger with increasing LDL cholesterol levels.

CONCLUSIONS

Our study identified a relationship between serum ferritin levels and carotid atherosclerosis that was potentiated by LDL cholesterol. This relationship adds support to the hypothesis of a link between iron and cardiovascular disease.

Atherosclerosis in Dialyzed Patients

In the recent HEMO study, the most common cause of death in dialyzed patients was ischemic heart disease. In Europe there are regional differences, but the mortality due to cardiovascular disease is also very high. The long-lasting controversy whether the high incidence and prevalence of atherosclerotic manifestations (particularly ischemic heart disease) may be explained by known risk factors, or non-traditional risk factors are also involved seems to be partially solved with the increasing evidence that the latter hypothesis is true. Thus, together with classic risk factors such as hypertension, dyslipidemia and diabetes, other situations such as microinflammation, increased concentration of asymmetrical dimethyl-L-arginine, disturbed phosphate metabolism and anemia may represent important risk factors for accelerated atherosclerosis in dialyzed patients.

Oxidative stress - a link between endothelial injury, coagulation activation, and atherosclerosis in haemodialysis patients

BACKGROUND/AIM

Recently emerging evidence suggests that oxidative stress (SOX) may participate in atherogenesis. The aim of the present study was to establish whether enhanced SOX, involving endothelial injury, activation of coagulation, and inflammatory reaction, could be implicated in atherosclerotic diseases in haemodialysis (HD) patients.

METHODS

Markers of SOX, endothelial injury, coagulation, and cytokines, were measured in the plasma of HD patients with and without cardiovascular disease (CVD), and of healthy controls by ELISA methods. Remodeling of the carotid arteries was assessed by measuring the intima-media thickness (IMT) as a surrogate of atherosclerotic disease in all groups.

RESULTS

Markers of SOX, endothelial injury, and extrinsic coagulation pathway activation and IMT values were significantly elevated in HD patients, especially in those with CVD when compared with the control group. The von Willebrand factor antigen (vWF:Ag) levels were more increased in the patients with CVD than in those without. Furthermore, the plasma levels of tumour necrosis factor alpha, monocyte chemo-attractant protein 1, and macrophage inflammatory protein 1 beta were significantly higher only in the HD group with CVD when compared with the controls. The IMT was strongly and directly correlated with Cu/Zn superoxide dismutase. Both IMT and Cu/Zn superoxide dismutase were positively correlated with age, thrombomodulin, vWF:Ag, tissue factor, tissue factor pathway inhibitor, prothrombin fragment F1 + 2, monocte chemo-attractant protein 1, macrophage inflammatory protein 1 beta, and tumour necrosis factor alpha levels. Multivariate analysis identified vWF:Ag as the only independent variable significantly associated with an increased IMT.

CONCLUSIONS

The present study suggests that enhanced SOX, involved pro-atherogenic cytokine and chemokines levels, endothelial injury, and coagulation activation may constitute a pathway for accelerated atherosclerosis in HD patients. The significant, independent association between IMT and vWF:Ag should be assessed in future studies to determine whether vWF:Ag elevation is causative or a by-product of the increased IMT.

A Study of the Response of Elderly Patients with End-Stage Renal Disease to Epoetin Alfa or Beta

BACKGROUND

Anaemia correction in patients with end-stage renal disease has been enhanced following the use of epoetin alfa or beta and there are a number of studies detailing its application. Dialysis centres are dealing with greater numbers of elderly patients and anaemia correction in these individuals may differ by virtue of co-existing comorbidity and their age.

OBJECTIVE

The aim of this study was to examine the response of the elderly patients to anaemia correction using a locally devised anaemia correction protocol while receiving dialysis.

METHODS

An incident, non-randomised, cohort observational study in a single centre was used to compare the correction of anaemia in a population of elderly (> or =65 years of age) and young dialysis patients. All incident patients starting peritoneal dialysis and haemodialysis (HD) between January 1998 and December 2000 were selected and treated using a locally devised anaemia correction protocol and observed for at least 1 year. Anaemia correction following adjustments for factors such as age, comorbidity, dialysis type, dialysis access type and predialysis nephrological care was assessed.

RESULTS

198 patients commenced dialysis with 86 elderly patients (mean age +/- SD 73.7 +/- 4.9 years). The elderly patients had similar periods of predialysis nephrological care as the younger patients. Most patients received HD and required a tunnelled dialysis catheter (TC) as vascular access. Equivalent numbers of elderly patients received peritoneal dialysis. Comorbid scores were greater in the elderly and patient survival was dependent upon these comorbid factors. Following the strict use of TCs, patient survival was similar to those patients commencing HD with arterio-venous fistulae. Anaemia correction in the elderly was similar to the younger patients, with a median haemoglobin of 11.3 g/dL. By 6 months of dialysis, most patients achieved the UK Renal Association anaemia correction standard (haemoglobin above 10 g/dL). The elderly patients maintained significantly higher serum ferritin levels throughout (median 209 microg/L) and required less epoetin alfa or beta (median 91.6 units/kg/wk), indicating that functional iron deficiency in the elderly dialysis patients is less. Intravenous iron sucrose doses were similar in both age groups and iron overload (serum ferritin above 800 microg/L) had been avoided following the use of the intravenous iron protocol.

CONCLUSION

The study has noted that elderly patients responded to anaemia corrective therapies as well as the younger patients, despite greater levels of comorbidity while requiring less epoetin alfa or beta.

Controversies in iron management

BACKGROUND

Iron therapy is required in hemodialysis patients receiving erythropoietic stimulators in order to achieve the target hemoglobin in the most efficient way. While oral iron has been disappointing in this regard, parenteral iron has been widely used, despite a significant incidence of severe side effects when iron dextran is used. The recent availability of a more effective form of oral iron (heme-iron), and safer forms of parenteral iron (iron sucrose and iron gluconate) has made iron management in this population simpler. Many questions remain, however, about the use, efficacy, and safety of these compounds in hemodialysis patients.

METHODS

Current literature was reviewed and combined with the authors' clinical experience to address a number of current questions regarding the use of iron in hemodialysis patients.

RESULTS

Although oral non-heme iron is infrequently sufficient to maintain iron stores in hemodialysis patients, recent studies suggest that heme-iron may be more useful in this regard. Heme-iron is absorbed to a greater extent than non-heme iron, and is better tolerated. Small studies have shown that when heme-iron is administered, less parenteral iron and lower doses of erythropoietin (EPO) are needed to maintain target hemoglobin. Current evidence suggests that both iron sucrose and iron gluconate are safer than iron dextran, and the latter should only be used in extraordinary circumstances. While in vitro studies have demonstrated some differences in the effects of iron sucrose and iron gluconate on cellular toxicity, the clinical importance of these has not been determined. Both compounds can be used safely for repletion and maintenance therapy, and doses of up to 300 mg of either are generally well tolerated when such higher doses are needed, as in peritoneal dialysis (PD) patients or chronic kidney disease (CKD) patients not on dialysis.

CONCLUSION

A number of questions remain regarding the appropriate use, efficacy, and potential toxicity of iron therapy in dialysis patients. Further prospective research should address the myriad questions raised in this review.

Impact of carotid atherosclerosis on long-term mortality in chronic hemodialysis patients

BACKGROUND

Cardiovascular event is the major cause of mortality in patients on maintenance hemodialysis. We prospectively tested the predictive values of atherosclerotic parameters for all-cause and cardiovascular outcomes in 219 hemodialysis patients (age, 58 +/- 13 years; time on hemodialysis, 13 +/- 7 years; male/female, 144/75).

METHODS

We measured blood homocysteine (Hcy), ultrasound carotid artery intima media thickness (IMT) and % aortic wall calcification at L2/3 region [% of calcification index in the abdominal aortic wall (%ACI)] by computed tomography (CT) scan, and followed all patients for 5 years.

RESULTS

During the follow-up periods, 54 patients (25%) died, 40 (74%) of them of cardiovascular causes. IMT was significantly higher in patients who expired (0.75 +/- 0.02 mm) than in those who survived (0.62 +/- 0.01 mm). IMT was significantly correlated with age (r = 0.47, P < 0.01) and %ACI (r = 0.27, P < 0.01). The survival rate during the observation was significantly lower in the final IMT third (58%) than in the first (90%) and the middle IMT third (80%) (P < 0.01). Multivariate Cox proportional hazards analysis revealed that diabetes and IMT became independent determinants of all-cause and cardiovascular death. Adjusted hazards ratios of all-cause and cardiovascular mortality for an increase of 0.1 mm in IMT were 1.31 (95% CI, 1.07 to 1.59) and 1.41 (95% CI, 1.12 to 1.76). In contrast, %ACI at abdominal aorta and blood Hcy did not affect their 5-year mortality.

CONCLUSION

These findings suggested that measurement of carotid artery IMT is useful for predicting long-term mortality in patients receiving maintenance hemodialysis.

Impairment of Transendothelial Leukocyte Migration by Iron Complexes

ABSTRACT. Although iron sucrose and iron gluconate are generally well tolerated in patients who are treated for renal anemia, recent clinical studies and cell culture experiments suggested significant toxicity and long-term side effects arising from the use of these iron complexes. Because of the possible role of iron in infection or cardiovascular disease, it was theorized that parenteral iron compounds influence endothelial and PMN interactionin vitro. A well-established double-chamber method was used to assess the effect of different concentrations of iron sucrose and iron gluconate (1, 25, 50, and 100 μg/ml) on the transendothelial migration of PMN. Preincubation of PMN and endothelial cells as well as preincubation of PMN alone with 25, 50, or 100 μg/ml iron resulted in a significant decrease in PMN migration. In contrast, after incubation of the endothelial cells alone with iron, no reduction in the transendothelial migration of PMN was observed. Preincubation of PMN and/or endothelial cells with 1 μg/ml iron did not lead to any decrease in the rate of migrated PMN. The only significant change in experiments with 1 μg/ml was an increase in PMN migration after preincubation of endothelial cells and PMN with iron gluconate. A four-way ANOVA showed a significant effect of the iron concentration (P< 0.000001), of type of iron complex (P< 0.005), of the preincubation of endothelial cell (P< 0.001), and of the preincubation of PMN with iron (P< 0.000001) on PMN diapedesis. It is concluded that iron sucrose and iron gluconate cause a significant inhibition of transendothelial migration of PMN. E-mail: Guerkan.Sengoelge@univie.ac.at

Apoptotic pathways involved in U937 cells exposed to LDL oxidized by hypochlorous acid

Oxidized low-density lipoproteins (oxLDL) play a critical role in atherogenesis. One oxidative pathway of LDL involves myeloperoxidase, which catalyzes the production of hypochlorous acid (HOCl) in monocytes. We investigated the apoptotic mechanism induced by oxLDL, generated by HOCl treatment of native LDL, in human monocytic U937 cell line. The involvement of the mitochondrial apoptotic pathway was analyzed in Bcl-2-overexpressing clones, generated from U937 cells. HOCl-oxLDL induced in U937 cells (i) a marked caspase-dependent increase of apoptosis, (ii) a loss of mitochondrial membrane potential, (iii) a specific activation of caspase-2, -3, -8, and -9, and (iv) a similar degree of apoptosis in presence or absence of anti-Fas and anti-TNF-R1 antibodies. Moreover, the degree of HOCl-oxLDL-induced caspase-3 and -8 activation, and apoptosis was significantly reduced in U937/Bcl-2 cells, with no activation of caspase-9. By contrast, Cu-oxLDL-mediated apoptosis in U937 cells involved exclusively the mitochondrial pathway. In conclusion, the mechanism of HOCl-oxLDL-induced apoptosis in monocytic U937 cells involves the two pathways of apical caspase activation: (i) death receptor-mediated caspase-8 and (ii) mitochondria-mediated caspase-9. This converges in the activation of executing caspases, including caspase-3, and apoptosis. The interference of Bcl-2 overexpression with HOCl-oxLDL-induced apoptosis suggests the importance of mitochondrial involvement in this apoptotic mechanism.

Nutritional requirements in maintenance hemodialysis

There is a high prevalence of nutritional disorders in maintenance hemodialysis patients. This fact has been recently confirmed because larger routine assessments of MHD patients body composition are now performed. Food records and dietary interviews show spontaneous low intakes of protein and energy in many patients. An increasing dialysis dose above a Kt/V (single pool) of 1.5 may not improve patients nutritional intakes. Inflammation may further impair the balance between protein synthesis and catabolism and cause anorexia. In response to these abnormalities, the management of energy, protein, vitamins, and trace elements intake will be discussed with special emphasis on calcium, phosphorus, enteral support, and parenteral nutrition.

AOPP-induced activation of human neutrophil and monocyte oxidative metabolism: a potential target for N-acetylcysteine treatment in dialysis patients

AOPP-induced activation of human neutrophil and monocyte oxidative metabolism: A potential target forN-acetylcysteine treatment in dialysis patients.

BACKGROUND

Oxidative stress largely contributes to hemodialysis-associated lethal complications, thus explaining the urgent need of antioxidant-based therapeutic strategies in hemodialysis patients. We previously identified advanced oxidation protein products (AOPP) in the uremic plasma as exquisite markers of oxidative stress and potent mediators of monocyte activation. The present study was aimed at searching whether (1) AOPP can also trigger activation of polymorphonuclear neutrophils (PMN), and (2) whether AOPP-induced activation could be inhibited by N-acetylcysteine (NAC), a widely used compound which has been shown to prevent oxidative injury to kidney.

METHODS

Both human serum albumin (HAS) AOPP (i.e., HOCl-modified HSA in vitro preparations and AOPP extracted from plasma of hemodialysis patients) were tested for their capacity to trigger phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase (MPO)-dependent activities as measured by lucigenin- and luminol-amplified chemiluminescence (CL), respectively, as compared to receptor-dependent [opsonized zymosan or receptor-independent phorbol myristate acetate (PMA)]. The effect of PMN priming by platelet-activating factor (PAF), and the effect of NAC on normal monocyte and on normal or hemodialysis patient's (N = 16) PMN oxidative responses were compared.

RESULTS

HSA-AOPP triggered in a HOCl dose-dependent manner both NADPH-oxidase- and MPO-dependent CL of PMN. This latter was further enhanced by PAF priming. Plasma-derived AOPP obtained from hemodialysis patients also triggered PMN respiratory burst. NAC significantly reduced HSA-AOPP-mediated responses of normal monocyte and of normal and uremic PMN but had no significant effect on opsonized zymosan- or PMA-induced CL responses.

CONCLUSION

This dual potential of NAC to inhibit phagocyte oxidative responses induced by HSA-AOPP without affecting those mediated by compounds mimicking pathogens supports the proposal of a therapeutic trial with NAC aimed at reducing oxidative stress-related inflammation in hemodialysis patients.

Safety in iron management

Intravenous (IV) iron therapy has become an integral part of hemodialysis management during the past several decades, and the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative guidelines recognize that most patients undergoing hemodialysis will require IV iron therapy on a regular basis to reach target hemoglobin (Hgb) levels. There now are three IV iron compounds available in the United States: iron dextran, sodium ferric gluconate, and iron sucrose. Although all have been proven effective for increasing Hgb/hematocrit levels, recent data show differences in their relative safety profiles. During the past two decades, more than 30 deaths have been attributed to the use of IV iron dextran. The two newer compounds available in the United States, sodium ferric gluconate and iron sucrose, have more favorable safety profiles, with the largest prospective safety comparison to date showing sodium ferric gluconate to be similar to placebo in the incidence of serious anaphylactoid-type reactions. This article reviews safety data surrounding the IV iron therapies.

Are advanced oxidation protein products potential uremic toxins?

Oxidative stress, defined as a disruption of the equilibrium between the generation of oxidants and the activity of anti-oxidant systems, plays a significant role in the development of the inflammatory syndrome associated with chronic renal failure and hemodialysis. In our recent work, the aim of which was to better characterize oxidative stress in dialysis patients, we described the presence of oxidized protein products, which we have termed advanced oxidation protein products (AOPP), in the plasma of dialysis patients and we proposed AOPP as new markers of oxidative stress and potential inflammatory mediators. AOPP represent an exquisite marker of phagocyte-derived oxidative stress, and their role in the pathophysiology of chronic renal failure and dialysis-related complications might be of great importance. Regarding the mechanisms of generation of AOPP, we pointed out the importance of myeloperoxidase and the subsequent generation of chlorinated oxidants, previously considered solely as microbicidal agents, in the formation of AOPP. Indeed, AOPP appear to act as true inflammatory mediators since they are able to trigger the oxidative burst and the synthesis of inflammatory cytokines in neutrophils, as well as in monocytes. Thus, it could be hypothesized that the AOPP, which arise from the reaction between chlorinated oxidants and plasma proteins, constitute new uremic toxins with pro-inflammatory effects.

[Atherosclerosis and uremia: signifance of non-traditional risk factors]

Arteriosclerosis, atherosclerosis and vascular calcification are causally related to the high morbidity and mortality of patients with chronic renal failure. Oxidative stress and carbonyl stress of uremia, dialysis procedure and/or intravenous iron therapy result in AGE (advanced glycation end-product), ALE (advanced lipoxidation end-product) and AOPP (advanced oxidation protein product) formation, favouring together with elevated CRP (C-reactive protein) levels the development of cardiovascular and cerebrovascular complications. Enhanced plasma levels of homocysteine and ADMA (asymmetric dimethylarginine) contribute to this process. In addition, in chronic renal insufficiency hyperphosphatemia and an enhanced calcium x phosphorus ion product are associated with the morbidity and mortality of the patients, particularly in the presence of fetuin deficiency. Phosphorus, AGEs and AOPPs, beside other factors, catalyze the conversion of vascular smooth muscle cells to osteoblast--like cells (particularly in the presence of monocytes/macrophages), resulting in bone matrix protein formation. Other risk factors, such as age, male sex, smoking, hypertension, diabetes, chronic inflammation, insulin resistance or dyslipidemia (enhanced non-HDL-cholesterol) also contribute to the atherosclerotic risk profile of the patient with chronic renal insufficiency. While there is growing understanding of the mechanisms involved in arteriosclerosis, atherosclerosis and vascular calcification in uremia, we are still missing effective therapeutic maneuvers for reduction of excess mortality in uremic patients.

The iron hypothesis of atherosclerosis and its clinical impact

The iron hypothesis as an alternative explanation for the gender difference in the incidence and mortality of atherosclerosis has provoked increased debates and public health concerns. In this review we summarize the historical and recent literature on the iron hypothesis and discuss several related clinical issues and their implications. Apart from misconstruction of study populations, lack of a good method to reflect the iron contents of tissues may be the major factor for causing inconsistent results from epidemiological studies. Published data from 11 countries clearly indicate that the mortality from cardiovascular diseases is correlated with liver iron. We propose that redox-active iron in tissue is the atherogenic portion of total iron stores. Recently developed magnetic resonance imaging techniques in combination with Fe chelators may allow future studies to examine this component of body iron in lesions and the whole body. Several clinical situations characterized by increased iron stores have been proposed as 'human models' suitable for further tests of the iron hypothesis. Patients with end-stage renal disease may be the most unique cohort, having significant increases in their iron stores, low-density lipoprotein (LDL) oxidation, and cardiovascular events. Other patient groups may be well suited for specific studies of different atherogenic events. With a better understanding of iron-driven oxidative damage, well controlled and effectively designed studies on these models will finally bring us to the truth of the iron hypothesis.