Hemodialysis and Protein Oxidation Products

Design of the Functional Dialysis Membrane with a Catalase Pseudoactive Center on the Surface

Here, we have designed a functional dialysis membrane with a catalase pseudoactive center on the surface. To make the catalase pseudoactive center, we have modified the regenerated cellulose dialysis membrane with methylated or octylated poly(1-vinylimidazole) (PVIm-Me or PVIm-Oc), followed by manganese or iron tetrakis(4-carboxyphenyl)porphyrin (Mn- or Fe-TCPP), using the layer-by-layer (LbL) method. As a result of the optimization, the dialysis membrane modified with 25 mol % methylated poly(1-vinylimidazole) [PVIm-Me(25)] and Mn-TCPP produced the highest amount of oxygen (O2) from hydrogen peroxide (H2O2) without the decomposition of Mn-TCPP. Conversely, Mn- and Fe-TCPP were decomposed under other experimental conditions in the presence of H2O2. These results suggest the conversion of H2O2 to O2 by catalase catalytic activity on the surface coated with PVIm-Me(25) and Mn-TCPP.

Practical Strategies to Reduce Ochratoxin A in Foods

Ochratoxin A (OTA), a potent nephrotoxin, is one of the most deleterious mycotoxins, with its prevalence in agricultural crops and their processed foods around the world. OTA is a major concern to food safety, as OTA exposure through dietary intake may lead to a significant level of accumulation in the body as a result of its long half-life (about 35 days). Its potent renal toxicity and high risk of exposure as well as the difficulty in controlling environmental factors OTA production has prompted the need for timely information on practical strategies for the food industry to effectively manage OTA contamination during food processing. The effects of various food processes, including both nonthermal and thermal methods, on the reduction in OTA were summarized in this review, with emphasis on the toxicity of residual OTA as well as its known and unknown degradation products. Since complete removal of OTA from foodstuffs is not feasible, additional strategies that may facilitate the reduction in OTA in food, such as adding baking soda and sugars, was also discussed, so that the industry may understand and apply practical measures to ensure the safety of its products destined for human consumption.

Biomarkers and Mechanisms of Oxidative Stress-Last 20 Years of Research with an Emphasis on Kidney Damage and Renal Transplantation

Oxidative stress is an imbalance between pro- and antioxidants that adversely influences the organism in various mechanisms and on many levels. Oxidative damage occurring concomitantly in many cellular structures may cause a deterioration of function, including apoptosis and necrosis. The damage leaves a molecular “footprint”, which can be detected by specific methodology, using certain oxidative stress biomarkers. There is an intimate relationship between oxidative stress, inflammation, and functional impairment, resulting in various diseases affecting the entire human body. In the current narrative review, we strengthen the connection between oxidative stress mechanisms and their active compounds, emphasizing kidney damage and renal transplantation. An analysis of reactive oxygen species (ROS), antioxidants, products of peroxidation, and finally signaling pathways gives a lot of promising data that potentially will modify cell responses on many levels, including gene expression. Oxidative damage, stress, and ROS are still intensively exploited research subjects. We discuss compounds mentioned earlier as biomarkers of oxidative stress and present their role documented during the last 20 years of research. The following keywords and MeSH terms were used in the search: oxidative stress, kidney, transplantation, ischemia-reperfusion injury, IRI, biomarkers, peroxidation, and treatment.

Advanced oxidation protein products in nondiabetic end stage renal disease patients on maintenance haemodialysis

In chronic kidney disease (CKD), the impairment of the excretory function leads to elevation in the blood concentrations of urea, creatinine, and various protein metabolic products. Advanced oxidation protein products (AOPP), along with protein carbonyls, protein-bound di-tyrosines and S-thiolated proteins, are considered biomarkers of oxidative stress in end-stage renal disease (ESRD) patients on maintenance haemodialysis (HD). In this study, we evaluated the correlations between plasma levels of AOPP (measured by size exclusion/gel filtration high performance liquid chromatography) and those of protein-bound di-tyrosines, protein carbonyls, albumin and fibrinogen in 50 nondiabetic ESRD patients on maintenance HD. Considering that AOPP could represent the bridge between oxidative stress and inflammation, having been identified as proinflammatory mediators, we also evaluated the association between AOPP levels, C-reactive protein concentration and white blood cells count. Finally, we assessed the associations between plasma level of AOPP and serum concentrations of creatinine and urea, both of which showed a strong dependence on the chronological age of haemodialysed patients. Taken together, our results confirm the robust relationship between uraemia and oxidative stress, especially when measured as biomarkers of severe protein oxidative damage (e.g. plasma AOPP).

Therapeutic Strategies for Oxidative Stress-Related Cardiovascular Diseases: Removal of Excess Reactive Oxygen Species in Adult Stem Cells

Accumulating evidence indicates that acute and chronic uncontrolled overproduction of oxidative stress-related factors including reactive oxygen species (ROS) causes cardiovascular diseases (CVDs), atherosclerosis, and diabetes. Moreover ROS mediate various signaling pathways underlying vascular inflammation in ischemic tissues. With respect to stem cell-based therapy, several studies clearly indicate that modulating antioxidant production at cellular levels enhances stem/progenitor cell functionalities, including proliferation, long-term survival in ischemic tissues, and complete differentiation of transplanted cells into mature vascular cells. Recently emerging therapeutic strategies involving adult stem cells, including endothelial progenitor cells (EPCs), for treating ischemic CVDs have highlighted the need to control intracellular ROS production, because it critically affects the replicative senescence of ex vivo expanded therapeutic cells. Better understanding of the complexity of cellular ROS in stem cell biology might improve cell survival in ischemic tissues and enhance the regenerative potentials of transplanted stem/progenitor cells. In this review, we will discuss the nature and sources of ROS, drug-based therapeutic strategies for scavenging ROS, and EPC based therapeutic strategies for treating oxidative stress-related CVDs. Furthermore, we will discuss whether primed EPCs pretreated with natural ROS-scavenging compounds are crucial and promising therapeutic strategies for vascular repair.

Accumulation of circulating advanced oxidation protein products is an independent risk factor for ischaemic heart disease in maintenance haemodialysis patients

AIM

Whether the burden of advanced oxidation protein products (AOPP) accumulation, a marker of oxidative stress, is affected by dialysis modality remains unclear. We compared the serum levels of AOPP in patients on haemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) and tested the hypothesis that an accumulation of AOPP was an independent risk factor for cardiovascular disease.

METHODS

This was a cross-section study. A total of 2095 patients (1539 HD, 556 CAPD) were recruited from the nine largest dialysis centres in China. Persons in medical centres for disease screening were selected as controls. Patients maintained on HD were dialyzed twice or thrice weekly. CAPD patients used lactate-buffered, glucose-containing solutions. The patients' data were abstracted from the medical record. The serum levels of AOPP were determined by spectrophotometric detection.

RESULTS

The levels of AOPP were significantly elevated in both HD and CAPD patients compared to healthy controls. Accumulation of AOPP was more significant in HD compared to CAPD population. Meanwhile, AOPP accumulation was associated with the presence of ischaemic heart disease (IHD) only in HD, but not CAPD patients. A higher proportion of IHD was found in the HD population among those with higher levels of AOPP in each category of age and irrespective of the presence or absence of high triglyceride. Multivariate regression analysis indicated that accumulation of AOPP was an independent risk factor for IHD in HD population.

CONCLUSION

Accumulation of AOPP was more significant in HD compared to CAPD patients. The level of AOPP was independently associated with IHD only in HD patients.

Base excision repair gene polymorphisms are associated with inflammation in patients undergoing chronic hemodialysis

Chronic inflammation may increase the risk of mortality for patients undergoing hemodialysis, while enhanced oxidative stress and DNA oxidative damage are involved in the inflammatory response. The purpose of this study was to examine the associations between inflammation and polymorphisms in the base excision repair (BER) system, which protects against oxidative DNA damage, among hemodialysis patients. Data were analyzed from 167 hemodialysis patients and 66 healthy controls. All subjects were evaluated for the expression of inflammatory cytokines (IL-1β and IL-6) and genotyped for two BER genes, including hOGG1 c.977C>G, MUTYH c.972G>C and AluYb8MUTYH. The results showed that the hemodialysis patients had significantly higher levels of IL-1β and IL-6 than the healthy controls. In the healthy controls, no patterns of association were observed between the hOGG1 c.977C>G or MUTYH c.972G>C genotypes and IL-1β or IL-6 levels; however, patients with the MUTYH c.972G/G genotype presented higher levels of IL-1β than those with the C/C genotype. The AluYb8MUTYH genotype was strongly associated with increased IL-1β levels among controls and increased IL-1β and IL-6 levels among hemodialysis patients. Additionally, the synergetic effect of these variations of the BER genes on the levels of IL-1β and IL-6 was investigated. The combinations of the AluYb8MUTYH genotype with the hOGG1 c.977 C>G or MUTYH c.972 G>C genotypes were associated with the IL-1β and IL-6 levels in hemodialysis patients. This is the first report showing an association between BER genetic polymorphisms and the inflammatory state during hemodialysis; this association might be mediated by impaired anti-oxidant defense mechanisms.

Evidence for a role of oxidative stress in the carcinogenicity of ochratoxin a

The in vitro and in vivo evidence compatible with a role for oxidative stress in OTA carcinogenicity has been collected and described. Several potential oxido-reduction mechanisms have been identified in the past. More recently, the possibility of a reduction of cellular antioxidant defense has been raised as an indirect source of oxidative stress. Consequences resulting from the production of oxidative stress are observed at different levels. First, OTA exposure has been associated with increased levels of oxidative DNA, lipid, and protein damage. Second, various biological processes known to be mobilized under oxidative stress were shown to be altered by OTA. These effects have been observed in both in vitro and in vivo test systems. In vivo, active doses were often within doses documented to induce renal tumors in rats. In conclusion, the evidence for the induction of an oxidative stress response resulting from OTA exposure can be considered strong. Because the contribution of the oxidative stress response in the development of cancers is well established, a role in OTA carcinogenicity is plausible. Altogether, the data reviewed above support the application of a threshold-based approach to establish safe level of dietary human exposure to OTA.

Linkage of some trace elements, peripheral blood lymphocytes, inflammation, and oxidative stress in patients undergoing either hemodialysis or peritoneal dialysis

BACKGROUND

Changes in essential trace elements may affect the inflammatory and immunological state of patients on hemodialysis (HD) or peritoneal dialysis (PD). Therefore, we aimed to determine trace element content and markers of oxidative stress, inflammation, and immune status in HD and PD patients and to assess the relationships among these parameters.

METHODS

Patients on either HD (n = 20) or PD (n = 20) and age-, sex-, body mass index-matched healthy individuals (n = 20) were enrolled in the study. The trace elements zinc, copper, selenium, and iron; markers of oxidative stress thiobarbituric acid reactive substances (TBARS) and protein carbonyl levels; activities of antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase; percentages of CD3 T lymphocytes and the subsets CD4 and CD8; the CD4/CD8 ratio; and C-reactive protein (CRP) were measured.

RESULTS

All dialysis patients had low levels of albumin and hemoglobin. Significantly decreased percentages of CD3 and CD4 T lymphocytes and increased levels of CRP, TBARS, and carbonyl compounds were observed in HD patients. HD patients also had elevated erythrocyte SOD, lower GPx and catalase activities, and decreased levels of Se, Zn, and Fe in comparison to PD patients and healthy subjects. In addition, CRP was positively associated with TBARS and carbonyl levels, but was significantly inversely associated with Zn and Se levels. Positive correlations were found between T lymphocyte CD3 and CD4 percentages and Zn, Se, and Fe levels.

CONCLUSIONS

There were significant decreases in T lymphocyte-related immunological regulation and increased inflammation and oxidative stress in dialysis patients. Essential trace element status was independently related to immune status, inflammation, and oxidative damage.

Uremic toxicity, oxidative stress, and hemodialysis as renal replacement therapy

Patients with uremia are subject to greatly increased cardiovascular risk that cannot be completely explained by traditional cardiovascular risk factors. An increase in oxidative stress and inflammation has been proposed as contributory nontraditional uremic cardiovascular risk factors. Oxidative stress reflects the balance between oxidant generation and antioxidant defense mechanisms. Reduction/oxidation (redox) reactions may result in a stochastic process leading to oxidation of neighboring macromolecules. However, in many instances the reactive oxygen species target particular amino acid residues or lipid moieties. This provides a mechanism by which increased oxidative stress and/or alteration of antioxidant mechanisms can alter cell signaling. In individuals with advanced chronic kidney disease, the redox balance is not in equilibrium and is tipped toward oxidation resulting in the dysregulation of cellular process with subsequent vascular and tissue injury. In this review, the major oxidant and antioxidant pathways and the biomarkers to assess redox status in uremia are discussed, as well as the data linking the pathogenesis of oxidative stress, inflammation, cardiovascular events, and the progressive loss of kidney function in chronic kidney disease.

Tipping the redox balance of oxidative stress in fibrogenic pathways in chronic kidney disease

Patients with moderate to advanced chronic kidney disease or end-stage renal disease have a greatly increased cardiovascular risk that cannot be explained entirely by traditional cardiovascular risk factors. An increase in oxidative stress and inflammation have been proposed as nontraditional cardiovascular risk factors in this patient population. Oxidative stress reflects the redox balance between oxidant generation and antioxidant mechanisms. The generation of reactive oxygen species is not simply a random process that oxidizes nearby macromolecules, but, in many instances, the oxidants target particular amino acid residues or lipid moieties. Oxidant mechanisms are now recognized to be intimately involved in cell signaling and to be vital components of the immune response. This is equally true for antioxidant mechanisms as well. In the progression of chronic kidney disease, the redox balance is not in equilibrium and is tipped toward oxidation, resulting in the dysregulation of cellular process and subsequent tissue injury. In this review we discuss the major oxidant and antioxidant pathways and the biomarkers to assess redox status. We also review the data linking the pathogenesis of oxidative stress, inflammation, and the progressive loss of kidney function in chronic kidney disease.

Effect of losartan on ambulatory short-term blood pressure variability and cardiovascular remodeling in hypertensive patients on hemodialysis

OBJECTIVE

Previous studies have shown increases in ambulatory short-term blood pressure (BP) variability to be related to cardiovascular disease. In this study, we examined whether an angiotensin II type 1 receptor blocker losartan would improve ambulatory short-term BP variability in hypertensive patients on hemodialysis.

METHODS

Forty hypertensive patients on hemodialysis therapy were randomly assigned to the losartan treatment group (n=20) or the control treatment group (n=20). At baseline and 6 and 12 months after the treatment, 24-h ambulatory BP monitoring was performed. Echocardiography and measurements of brachial-ankle pulse wave velocity (baPWV) and biochemical parameters were also performed before and after therapy.

RESULTS

After 6- and 12-months of treatment, nighttime short-term BP variability, assessed on the basis of the coefficient of variation of ambulatory BP, was significantly decreased in the losartan group, but remained unchanged in the control group. Compared with the control group, losartan significantly decreased left ventricular mass index (LVMI), baPWV, and the plasma levels of brain natriuretic peptide and advanced glycation end products (AGE). Furthermore, multiple regression analysis showed significant correlations between changes in LVMI and changes in nighttime short-term BP variability, as well as between changes in LVMI and changes in the plasma levels of AGE.

CONCLUSION

These results suggest that losartan is beneficial for the suppression of pathological cardiovascular remodeling though its inhibitory effect on ambulatory short-term BP variability during nighttime.

Serum Concentrations of F2-Isoprostanes and 4-Hydroxynonenal in Hemodialysis Patients in Relation to Inflammation and Renal Anemia

Background

Patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) are apparently exposed to enhanced oxidative stress and to inflammation. It was the aim of this study to characterize the state of systemic oxidative stress of ESRD patients before and following HD using highly specific biomarkers, F₂-isoprostanes and 4-hydroxynonenal (HNE). Furthermore the question should be answered, if there are associations between inflammation and systemic oxidative stress and/or between systemic oxidative stress and renal anemia, which is more or less typical for HD patients.

Patients and methods

Concentrations of F₂-isoprostanes, HNE, C-reactive protein (CRP) as marker of inflammation, and hemoglobin were measured in serum samples of patients with ESRD before and after HD and of healthy control persons for comparison. Total (esterified plus free) F₂-isoprostanes were quantified by highly sensitive gas chromatography/mass spectrometry technique, HNE by thin layer chromatography and HPLC/UV detection, CRP by immunoturbidimetry and hemoglobin by clinico-chemical routine assay.

Results

1. HD patients showed significantly higher serum concentrations of F₂-isoprostanes and HNE than healthy human control subjects. 2. Total (esterified plus free) F₂-isoprostane levels before HD were not significantly different from those after HD, whereas HNE levels were significantly decreased in patients after HD. 3. F₂-isoprostane concentrations in HD patients correlated with the levels of CRP, whereas HNE concentrations inversely correlated with the content of hemoglobin.

Conclusion

Both, F₂-isoprostanes and HNE serum concentrations are useful oxidative stress parameters in ESRD patients undergoing HD. Whereas HNE strongly correlates with the severity of renal anemia, leading to left heart insufficiency, F₂-isoprostanes (sum of free plus esterified) highly correlate with the degree of inflammation.