Effects of a vitamin E-modified dialysis membrane on neutrophil superoxide anion radical production

Hemodialysis raises oxidative stress through carbon-centered radicals despite improved biocompatibility

Leukocyte activation and the resulting oxidative stress induced by bioincompatible materials during hemodialysis impact the prognosis of patients. Despite multiple advances in hemodialysis dialyzers, the prognosis of hemodialysis patients with complications deeply related to oxidative stress, such as diabetes mellitus, remains poor. Thus, we re-evaluated the effects of hemodialysis on multiple reactive oxygen species using electron spin resonance-based methods for further improvement of biocompatibility in hemodialysis. We enrolled 31 patients in a stable condition undergoing hemodialysis using high-flux polysulfone dialyzers. The effects of hemodialysis on reactive oxygen species were evaluated by two methods: MULTIS, which evaluates serum scavenging activities against multiple hydrophilic reactive oxygen species, and i-STrap, which detects lipophilic carbon-center radicals. Similar to previous studies, we found that serum hydroxyl radical scavenging activity significantly improved after hemodialysis. Unlike previous studies, we discovered that scavenging activity against alkoxyl radical was significantly reduced after hemodialysis. Moreover, patients with diabetes mellitus showed a decrease in serum scavenging activity against alkyl peroxyl radicals and an increase in lipophilic carbon-center radicals after hemodialysis. These results suggest that despite extensive improvements in dialyzer membranes, the forms of reactive oxygen species that can be eliminated during dialysis are limited, and multiple reactive oxygen species still remain at increased levels during hemodialysis.

A pilot study to determine the dose and effectiveness of adrenocorticotrophic hormone (H.P. Acthar® Gel) in nephrotic syndrome due to idiopathic membranous nephropathy

Background

H.P. Acthar® Gel is currently the only Food and Drug Administration therapy approved for the treatment of nephrotic syndrome. Active drug ingredients include structurally related melanocortin peptides that bind to cell surface G-protein-coupled receptors known as melanocortin receptors, which are expressed in glomerular podocytes. In animal models of membranous nephropathy, stimulation has been demonstrated to reduce podocyte injury and loss. We hypothesized that H.P. Acthar® Gel would improve symptoms of the nephrotic syndrome in patients with idiopathic membranous nephropathy.

Methods

Twenty patients received a subcutaneous dose of 40 or 80 IU twice weekly. Changes in proteinuria, albumin, cholesterol profile, estimated glomerular filtration rate and serum anti-PLA₂R antibodies were assessed at baseline and in response to treatment along with tolerance and safety.

Results

Baseline characteristics included mean proteinuria (9.1 ± 3.4 g/day), albumin (2.7 ± 0.8 g/dL), estimated glomerular filtration rate (77 ± 30 mL/min) along with elevated total and low-density lipoprotein (LDL) cholesterol. By 12 months of follow-up, there was a significant improvement in proteinuria in the entire cohort, decreasing to 3.87 ± 4.24 g/day (P < 0.001) with significant improvements in serum albumin, total and LDL cholesterol. A >50% decrease in proteinuria was noted in 65% of the patients with a trend toward better outcomes among patients who received greater cumulative doses. No significant adverse effects were documented. Clearing of serum anti-PLA₂R antibodies prior to or in parallel with proteinuria improvement was noted in some, but not all patients.

Conclusions

H.P. Acthar® Gel is a potential therapy for nephrotic syndrome secondary to idiopathic membranous nephropathy that deserves further study.

Vitamin E-derived copolymers continue the challenge to hemodialysis biomaterials

Improving material biocompatibility has been a continuous effort and remains a major goal of dialysis therapy. In this respect, vitamin E-modified copolymers have been used to produce a generation of biomaterials that has offered new clinical challenges and the chance of further improving the quality of synthetic hemodialyser membranes. This mini review article describes the evolution of these copolymers that only recently have been adopted to develop new vitamin E-modified polysulfone hemodialysers. Biomaterial characteristics and clinical aspects of these membranes are discussed, starting from the most recent contributions that have appeared in the literature that are of interest for the community of nephrology and dialysis specialists, as well as biomaterial scientists.

Clusterin attenuates the development of renal fibrosis

Upregulation of clusterin occurs in several renal diseases and models of nephrotoxicity, but whether this promotes injury or is a protective reaction to injury is unknown. Here, in the mouse unilateral ureteral obstruction model, obstruction markedly increased the expression of clusterin, plasminogen activator inhibitor-1 (PAI-1), type I collagen, and fibronectin. Compared with wild-type mice, clusterin-deficient mice exhibited higher levels of PAI-1, type I collagen, and fibronectin and accelerated renal fibrosis in response to obstruction. In cultured rat tubular epithelium-like cells, adenovirus-mediated overexpression of clusterin inhibited the expression of TGF-β-stimulated PAI-1, type I collagen, and fibronectin. Clusterin inhibited TGF-β-stimulated Smad3 activity via inhibition of Smad3 phosphorylation and its nuclear translocation. Moreover, intrarenal delivery of adenovirus-expressing clusterin upregulated expression of clusterin in tubular epithelium-like cells and attenuated obstruction-induced renal fibrosis. In conclusion, clusterin attenuates renal fibrosis in obstructive nephropathy. These results suggest that upregulation of clusterin during renal injury is a protective response against the development of renal fibrosis.

Effect of leptin on polymorphonuclear leucocyte functions in healthy subjects and haemodialysis patients

BACKGROUND

Dysfunction of polymorphonuclear leucocytes (PMNLs) in end-stage renal disease (ESRD) patients contributes to a diminished immune defence. The serum levels of leptin are elevated in patients with ESRD. We analysed in vitro effects of leptin on PMNLs from healthy subjects (HS; n = 12) and haemodialysis (HD) patients (n = 15) before and after HD.

METHODS

PMNL oxidative burst and phagocytosis were tested by flow cytometry in whole blood. Chemotaxis of isolated PMNLs was assessed by the under-agarose method. To assess the involvement of leptin in PMNL signalling pathways, signal transduction inhibitors were used and the activity of intracellular kinases was investigated by western blotting, in vitro kinase assays and the Luminex technology.

RESULTS

Increasing the leptin level in the blood of HS leads to a reduced activation of the oxidative burst by Escherichia coli and phorbol 12-myristate 13-acetate. Activation of the oxidative burst is reduced in the blood of HD patients and the addition of leptin does not lead to further PMNL inhibition. Leptin at a concentration measured in HD patients significantly reduces the chemotaxis of PMNLs from HS but had no effect on PMNLs from ESRD patients before and also after HD treatment with high-flux dialysers. The phosphoinositide 3-kinase/Akt pathway is involved in the inhibitory effects of leptin.

CONCLUSIONS

In the presence of leptin, PMNLs from HS and HD patients respond differently to stimuli. The lack of response to leptin in PMNLs from HD patients cannot be influenced by HD.

siRNA-based therapy ameliorates glomerulonephritis

RNA interference by short interfering RNAs (siRNAs) holds promise as a therapeutic strategy, but use of siRNAs in vivo remains limited. Here, we developed a system to target delivery of siRNAs to glomeruli via poly(ethylene glycol)-poly(l-lysine)-based vehicles. The siRNA/nanocarrier complex was approximately 10 to 20 nm in diameter, a size that would allow it to move across the fenestrated endothelium to access to the mesangium. After intraperitoneal injection of fluorescence-labeled siRNA/nanocarrier complexes, we detected siRNAs in the blood circulation for a prolonged time. Repeated intraperitoneal administration of a mitogen-activated protein kinase 1 (MAPK1) siRNA/nanocarrier complex suppressed glomerular MAPK1 mRNA and protein expression in a mouse model of glomerulonephritis; this improved kidney function, reduced proteinuria, and ameliorated glomerular sclerosis. Furthermore, this therapy reduced the expression of the profibrotic markers TGF-beta1, plasminogen activator inhibitor-1, and fibronectin. In conclusion, we successfully silenced intraglomerular genes with siRNA using nanocarriers. This technique could aid the investigation of molecular mechanisms of renal disease and has potential as a molecular therapy of glomerular diseases.

Development of a device for chemiluminescence determination of superoxide generated inside a dialysis hollow-fiber membrane

Reactive oxygen species (ROS) generated during hemodialysis treatment cause dialysis complications because of the high reactivity of ROS. To prevent dialysis complications caused by oxidative stress, it is important to evaluate the generation and dismutation of ROS during hemodialysis treatment. In this study, our aim was to develop a device to determine superoxide (O(2)(-)) generated inside a dialysis hollow fiber, and also to examine whether this device could detect O(2)(-) separated from plasma using hollow fibers. Experimental apparatus was set up so that hypoxanthine (HX) solution flowed inside the hollow fibers and 2-methyl-6-p-methoxyphenylethynyl-imidazopyrazinone (MPEC) solution flowed outside the hollow fibers. Then, xanthine oxidase (XOD) solution was added to the HX solution to generate O(2)(-), and chemiluminescence resulting from the reaction of O(2)(-) with MPEC was measured with an optical fiber. Chemiluminescence intensity was measured at different HX concentrations, and the peak area of relative luminescence intensity yielded a first-order correlation with the HX concentration. Based on the relationship between HX and O(2)(-) concentrations determined by the cytochrome c reduction method, the relative luminescence intensity measured by this device was linearly dependent on the O(2)(-) concentration inside the hollow fibers. After modifications were made to the device, XOD solution injection into plasma including HX resulted in an increase in the relative luminescence intensity. We concluded that this novel device based on chemiluminescence is capable of determining aqueous O(2)(-) generated inside a hollow fiber and also of detecting O(2)(-) in plasma.

Comparative effects of dietary supplementation with red grape juice and vitamin E on production of superoxide by circulating neutrophil NADPH oxidase in hemodialysis patients

BACKGROUND

Atherosclerotic cardiovascular disease is the most common cause of death among hemodialysis patients; it has been attributed to increased oxidative stress, dyslipidemia, malnutrition, and chronic inflammation. Activation of neutrophils is a well-recognized feature in dialysis patients, and superoxide-anion production by neutrophil NADPH oxidase may contribute significantly to oxidative stress.

OBJECTIVE

The aim of the study was to compare the effects of dietary supplementation with concentrated red grape juice (RGJ), a source of polyphenols, and vitamin E on neutrophil NADPH oxidase activity and other cardiovascular risk factors in hemodialysis patients.

DESIGN

Thirty-two patients undergoing hemodialysis were recruited and randomly assigned to groups to receive dietary supplementation with RGJ, vitamin E, or both or a control condition without supplementation or placebo. Blood was obtained at baseline and on days 7 and 14 of treatment.

RESULTS

RGJ consumption but not vitamin E consumption reduced plasma concentrations of total cholesterol and apolipoprotein B and increased those of HDL cholesterol. Both RGJ and vitamin E reduced plasma concentrations of oxidized LDL and ex vivo neutrophil NADPH oxidase activity. These effects were intensified when the supplements were used in combination; in that case, reductions in the inflammatory biomarkers intercellular adhesion molecule 1 and monocyte chemoattractant protein 1 also were observed.

CONCLUSIONS

Regular ingestion of concentrated RGJ by hemodialysis patients reduces neutrophil NADPH-oxidase activity and plasma concentrations of oxidized LDL and inflammatory biomarkers to a greater extent than does that of vitamin E. This effect of RGJ consumption may favor a reduction in cardiovascular risk.

Elimination of lipid peroxide during hemodialysis

BACKGROUND/AIMS

This study is aimed to show the antioxidative effect of hemodialysis (HD) by demonstrating the elimination of toxic lipid peroxides.

METHODS

Blood samples were obtained from patients on regular maintenance HD before and 15, 30, 60, 120 and 240 min after the start of each HD session. Plasma cholesteryl ester hydroperoxide (CE-OOH), phosphatidylcholine hydroperoxide (PC-OOH), and eliminators of lipid peroxides (LOOH) such as apolipoprotein A-I (apoA-I) and lecithin:cholesterol acyltransferase (LCAT) were investigated. The hydroxyl radical scavenging activity was measured for the evaluation of the pro-oxidative side.

RESULTS

CE-OOH and PC-OOH were elevated in patients with chronic kidney disease both on and not on HD, while these values were much higher in HD patients. CE-OOH quickly dropped during the first 30 min of HD, then gradually decreased until 240 min. CE-OOH concentrations were related to those of apoA-I. In contrast, PC-OOH showed an increase 30 min after the start of HD, a change which resembled that of LCAT and was the reverse of the hydroxyl radical scavenging activity.

CONCLUSION

These results demonstrate the antioxidative action through CE-OOH elimination involving apoA-I. The pro- and antioxidative effects of HD on LOOH are not uniform but PC-OOH is mainly influenced prooxidatively.

A systematic review of the effect of the Excebrane dialyser on biomarkers of lipid peroxidation

BACKGROUND

Oxidative stress is prevalent in dialysis patients and has been implicated in the pathogenesis of cardiovascular disease and anaemia. We conducted a systematic review and meta-analysis to examine the effect of Excebrane, a vitamin E-coated cellulose-based dialyser, on circulating biomarkers of lipid peroxidation, as surrogate markers of oxidative stress.

METHODS

The primary sources used to identify candidate studies included PubMed, the Cochrane Central Register of Controlled Trials, a bibliography provided by the dialyser manufacturer, and a manual search of abstracts from proceedings of scientific meetings and review articles. Studies were selected for analysis if their design included a comparator group (primarily within patient comparison, i.e. pre- and post-study evaluations). For the meta-analysis, we computed the overall change of the outcome from baseline using a random-effects model. A supplemental analysis was performed in which the absolute levels of these biomarkers of lipid peroxidation were converted to a common unit by calculating standardized effect sizes.

RESULTS

Fourteen peer-reviewed articles met the criteria. The studies consisted of 11 single arm, one randomized crossover and two randomized controlled trials, with a total of 37 to 158 evaluable patients, according to the outcome of interest analysed. Due to the paucity of randomized trials, the meta-analysis was limited to the Excebrane arm of each study. When the studies were combined according to similar measurement units, the overall mean decrease in malondialdehyde (MDA) level was -0.3 mM (95% CI, -0.5 to -0.1 mM; seven studies) and -0.8 nmol/mg low-density lipoprotein (LDL) (95% CI, -1.3 to -0.4 nmol/mg LDL; three studies), respectively. The summary estimate revealed a non-significant decrease in pre-dialysis thiobarbituric acid reactive substances (TBARS) level of 0.4 microM (95% CI, -1.2 to 0.4 microM; three studies). When the MDA and TBARS studies were combined using the standardized effect size, the mean decrease in these biomarkers of lipid peroxidation was statistically significant at -1.7 units (95% CI, -2.7, -0.7 units; 13 studies). A meta-analysis on the effect of Excebrane on pre-dialysis levels of oxidized-LDL could not be performed due to study heterogeneity.

CONCLUSION

The conversion of dialysis patients to a vitamin E-coated dialyser is associated with an improvement in circulating biomarkers of lipid peroxidation, which is of potential clinical benefit.

Imbalance between production and scavenging of hydroxyl radicals in patients maintained on hemodialysis

BACKGROUND

Reactive oxygen species are as being related to the pathophysiology of endstage renal disease (ESRD). We measured the plasma hydroxyl radical (.OH)-producing ability and .OH-scavenging activity in patients with ESRD to clarify the pathophysiological states involved.

METHODS

We used electron spin resonance to measure plasma N-t-butyl-alpha-phenylnitron radical spin adduct (pPBN rsa) as .OH-producing ability and plasma 3,3,5,5-tetramethyl-1-pyrroline-N-oxide radical spin adduct (pM4PO rsa) as .OH-scavenging activity. Oxidative injuries were evaluated by determining oxidised low-density lipoprotein (Ox-LDL).

RESULTS

The pPBN rsa of the ESRD patients was lower than that of the controls (1.83 vs 2.94 micromol/g protein). The pM4PO rsa of the ESRD patients was higher than that of the controls (3.85 vs 3.15 mmol L: -ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl hydrogen phosphate] potassium salt (EPC-K1)/g protein). The pPBN rsa and pM4PO rsa were correlated, both in the ESRD patients and in the controls (r = 0.47 and r = 0.53). Ox-LDL was correlated with hemodialysis (HD) duration (r = 0.49) and was negatively correlated with pPBN rsa (r = -0.54), which indicates that oxidative stress was increased as HD therapy was prolonged and suppressed pPBN rsa.

CONCLUSIONS

There was an imbalance between .OH-producing ability and .OH-scavenging activity, in the ESRD patients, and this may be responsible for compromising the health of ESRD patients.

Clusterin: a protective mediator for ischemic cardiomyocytes?

We examined the relationship between clusterin and activated complement in human heart infarction and evaluated the effect of this protein on ischemic rat neonatal cardiomyoblasts (H9c2) and isolated adult ventricular rat cardiomyocytes as in vitro models of acute myocardial infarction. Clusterin protects cells by inhibiting complement and colocalizes with complement on jeopardized human cardiomyocytes after infarction. The distribution of clusterin and complement factor C3d was evaluated in the infarcted human heart. We also analyzed the protein expression of clusterin in ischemic H9c2 cells. The binding of endogenous and purified human clusterin on H9c2 cells was analyzed by flow cytometry. Furthermore, the effect of clusterin on the viability of ischemically challenged H9c2 cells and isolated adult ventricular rat cardiomyocytes was analyzed. In human myocardial infarcts, clusterin was found on scattered, morphologically viable cardiomyocytes within the infarcted area that were negative for complement. In H9c2 cells, clusterin was rapidly expressed after ischemia. Its expression was reduced after reperfusion. Clusterin bound to single annexin V-positive or annexin V and propidium iodide-positive H9c2 cells. Clusterin inhibited ischemia-induced death in H9c2 cells as well as in isolated adult ventricular rat cardiomyocytes in the absence of complement. We conclude that ischemia induces the upregulation of clusterin in ischemically challenged, but viable, cardiomyocytes. Our data suggest that clusterin protects cardiomyocytes against ischemic cell death via a complement-independent pathway.

Antioxidant therapy in uremia: evidence-based medicine?

Because of correlations between cardiovascular disease, inflammation, and renal failure, many investigators are pursuing nontraditional risk factors and therapies in order to reduce cardiovascular morbidity and mortality in the end-stage renal disease (ESRD) population. Despite the disappointing lack of clinical effects with antioxidative therapies seen in large studies of the general population, some studies suggest a diminished cardiovascular risk in individuals with renal failure. This expanding new line of evidence is promising as a method to help alleviate the more than 20-fold increase in risk of cardiovascular events in the ESRD population. Most of the current available studies have evaluated laboratory or physiologic endpoints, such as endothelial function and measures of oxidative burden, and have evaluated relatively small numbers of patients. However, it is currently premature to initiate widespread clinical therapy with antioxidants. Further investigation in this area should be supported to see if reported benefits can be duplicated in more widespread study populations, and to more accurately define the most appropriate choice of therapy, mode of therapy, and dose.

Oxidative stress during leukocyte absorption apheresis

Leukocyte absorption apheresis absorbs leukocytes to the apheresis columns involving leukocyte activation. This process is regarded as bioincompatible and avoided in hemodialysis or other extracorporeal circulation processes. Thus, leukocyte apheresis has a potential risk to exacerbate in vivo oxidative stress. We evaluated the changes in plasma oxidative stress during leukocyte apheresis. Patients diagnosed as ulcerative colitis (UC) and treated with leukocyte apheresis were studied. Adacolumn (celluloseacetate beads) or Cellsorba EX (polyethylenephtarate fiber) was used for the leukocyte absorption device. Oxidative stress was measured by thiobarbituric acid reactive substances (TBARS) and hydroxyl radical ((*)OH) scavenging activity. Plasma samples were collected from the pre- and post-column sampling port at the start, and from the pre-column sampling port at the end of the treatment. The (*)OH signal intensities (OHRI) significantly increased during a column passage, indicating a loss of plasma (*)OH scavenging activity. However, OHRI was reduced at the end, suggesting a recovery of radical scavenging activity during leukocyte apheresis. Significant decreases of OHRI and TBARS were only observed in the early phase of the therapeutic course. No differences of OHRI and TBARS levels were observed between the two columns. These results indicate that though the plasma antioxidant activity was diminished by a column passage, plasma antioxidant activity recovers during the procedure. This efficient antioxidative effect is limited to the early phase of the therapeutic course.

Vitamin E-bonded hemodialyzer improves atherosclerosis associated with a rheological improvement of circulating red blood cells

BACKGROUND

Vitamin E-bonded hemodialyzer is known to improve oxidative stress in patients with hemodialysis. However, there is little information available as to whether or not this membrane clinically improves atherosclerosis. Furthermore, it remains unknown whether there is any effect of the membrane on rheology of circulating red blood cells.

METHOD

We conducted a randomized, open-labeled, prospective control study (N = 34) for 1 year to investigate the effect of vitamin E-bonded cellulose membrane dialyzer (EE) (N = 17) on carotid atherosclerotic changes [intima-media thickness (IMT) of carotid arteries] and the viscosity, percentage of dysmorphism (%DMR) of red blood cells (RBCs) and their distribution width-standard deviation (RDW-SD), in comparison with cellulose membrane (SU) (N = 17) identical to EE without vitamin E-bonded membrane. Erythropoietin (EPO) dose used for the treatment of uremic anemia was also calculated.

RESULTS

The IMT significantly decreased in the EE group, while in the SU group the IMT significantly increased. The viscosity of RBCs in hemodialysis patients (4.70 +/- 0.45 cP) was greater than that in healthy individuals (3.73 +/- 0.15 cP). EE significantly improved the viscosity (from 4.84 +/- 0.41 cP to 4.51 +/- 0.54 cP, P < 0.01), %DMR (from 2.29 +/- 2.17% to 1.90 +/- 1.49%, P < 0.01), and RDW-SD (from 54.4 +/- 7.6 fL to 49.3 +/- 5.9 fL, P < 0.01). On the contrary, these parameters all worsened in the SU group. EPO dose needed for the treatment of anemia was significantly (P < 0.05) reduced from 5383 +/- 2655 U/week to 4235 +/- 3103 U/week in the EE group. During these period, mean blood pressure, Kt/V urea, and serum beta2-microglobulin were not changed between the two groups.

CONCLUSION

These findings suggest that vitamin E-bonded hemodialyzer is very useful for improving atherosclerosis from a clinical point of view. As one of the underlying mechanisms, as well as antioxidant effects, we want to address an important role of the improvement of rheology of circulating RBCs, which may also help to reduce the requirement of EPO dose in the treatment of anemia of ESRD patients.

Apolipoprotein J/clusterin prevents a progressive glomerulopathy of aging

Apoliprotein J (apoJ)/clusterin has attracted considerable interest based on its inducibility in multiple injury processes and accumulation at sites of remodeling, regression, and degeneration. We therefore sought to investigate apoJ/clusterin's role in kidney aging, as this may reveal the accumulated effects of diminished protection. Aging mice deficient in apoJ/clusterin developed a progressive glomerulopathy characterized by the deposition of immune complexes in the mesangium. Up to 75% of glomeruli in apoJ/clusterin-deficient mice exhibited moderate to severe mesangial lesions by 21 months of age. Wild-type and hemizygous mice exhibited little or no glomerular pathology. In the apoJ/clusterin-deficient mice, immune complexes of immunoglobulin G (IgG), IgM, IgA, and in some cases C1q, C3, and C9 were detectable as early as 4 weeks of age. Electron microscopy revealed the accumulation of electron-dense material in the mesangial matrix and age-dependent formation of intramesangial tubulo-fibrillary structures. Even the most extensively damaged glomeruli showed no evidence of inflammation or necrosis. In young apoJ/clusterin-deficient animals, the development of immune complex lesions was accelerated by unilateral nephrectomy-induced hyperfiltration. Injected immune complexes localized to the mesangium of apoJ/clusterin-deficient but not wild-type mice. These results establish a protective role of apoJ/clusterin against chronic glomerular kidney disease and support the hypothesis that apoJ/clusterin modifies immune complex metabolism and disposal.