Oxidative stress and uremia

Impact of Intravenous Iron on Oxidative Stress and Mitochondrial Function in Experimental Chronic Kidney Disease

Background: Mitochondrial dysfunction is observed in chronic kidney disease (CKD). Iron deficiency anaemia (IDA), a common complication in CKD, is associated with poor clinical outcomes affecting mitochondrial function and exacerbating oxidative stress. Intravenous (iv) iron, that is used to treat anaemia, may lead to acute systemic oxidative stress. This study evaluated the impact of iv iron on mitochondrial function and oxidative stress. Methods: Uraemia was induced surgically in male Sprague-Dawley rats and studies were carried out 12 weeks later in two groups sham operated and uraemic (5/6 nephrectomy) rats not exposed to i.v. iron versus sham operated and uraemic rats with iv iron. Results: Induction of uraemia resulted in reduced iron availability (serum iron: 31.1 ± 1.8 versus 46.4 ± 1.4 µM), low total iron binding capacity (26.4 ± 0.7 versus 29.5 ± 0.8 µM), anaemia (haematocrit: 42.5 ± 3.0 versus 55.0 ± 3.0%), cardiac hypertrophy, reduced systemic glutathione peroxidase activity (1.12 ± 0.11 versus 1.48 ± 0.12 U/mL), tissue oxidative stress (oxidised glutathione: 0.50 ± 0.03 versus 0.36 ± 0.04 nmol/mg of tissue), renal mitochondrial dysfunction (proton/electron leak: 61.8 ± 8.0 versus 22.7 ± 5.77) and complex I respiration (134.6 ± 31.4 versus 267.6 ± 26.4 pmol/min/µg). Iron therapy had no effect on renal function and cardiac hypertrophy but improved anaemia and systemic glutathione peroxidase (GPx) activity. There was increased renal iron content and complex II and complex IV dysfunction. Conclusion: Iron therapy improved iron deficiency anaemia in CKD without significant impact on renal function or oxidant status.

Proanthocyanidins against Oxidative Stress: From Molecular Mechanisms to Clinical Applications

Proanthocyanidins (PCs) are naturally occurring polyphenolic compounds abundant in many vegetables, plant skins (rind/bark), seeds, flowers, fruits, and nuts. Numerous in vitro and in vivo studies have demonstrated myriad effects potentially beneficial to human health, such as antioxidation, anti-inflammation, immunomodulation, DNA repair, and antitumor activity. Accumulation of prooxidants such as reactive oxygen species (ROS) exceeding cellular antioxidant capacity results in oxidative stress (OS), which can damage macromolecules (DNA, lipids, and proteins), organelles (membranes and mitochondria), and whole tissues. OS is implicated in the pathogenesis and exacerbation of many cardiovascular, neurodegenerative, dermatological, and metabolic diseases, both through direct molecular damage and secondary activation of stress-associated signaling pathways. PCs are promising natural agents to safely prevent acute damage and control chronic diseases at relatively low cost. In this review, we summarize the molecules and signaling pathways involved in OS and the corresponding therapeutic mechanisms of PCs.

Oxidative and Nitrosative Stress in Stable Renal Transplant Recipients with Respect to the Immunosuppression Protocol - Differences or Similarities?

Background

The aim of the study was to evaluate parameters of oxidative and nitrosative stress as well as antioxidative parameters in a group of renal transplant recipients with stable graft function and no clinical signs of cardiovascular disease. We also aimed to determine the correlations among these parameters and to evaluate potential differences in all the biomarkers with regard to the immunosuppression protocol.

Methods

We enrolled 57 renal transplant recipients and 31 controls who were age and sex matched with the renal transplant recipients. All of the patients included in this study had post-renal transplant surgery at least 12 months earlier and were on standard immunosuppressive therapy. In this study, we determined thiobarbituric acid-reactive substances in plasma and red blood cells and advanced oxidation protein products, nitrosative stress parameters (asymmetric and symmetric dimethylarginine – ADMA and SDMA), and antioxidative parameters (total SH groups and catalase activity).

Results

The results of our study demonstrated that the levels of oxidative and nitrosative stress were significantly increased compared to the healthy population (p<0.01 except for plasma catalase activity p<0.05). Correlation analysis showed significant positive correlations between: ADMA and SDMA (p<0.01); ADMA and nitrates (p<0.05); SDMA and nitrates (p<0.05); between OS parameters in the experimental group; AOPP and SH groups (p<0.05) and TBARS in plasma and SH groups (p<0.01), SDMA and AOPP (p< 0.05); SDMA and TBARS in plasma (p<0.05); SDMA and SH groups (p<0.01); nitrates and SH groups (p<0.05).

Conclusion

There was no significant difference in oxidative and nitrosative stress parameters with respect to the immunosuppressive protocol.

High-efficiency on-line haemodiafiltration improves conduit artery endothelial function compared with high-flux haemodialysis in end-stage renal disease patients

BACKGROUND

Middle molecular weight uraemic toxins are considered to play an important role in vascular dysfunction and cardiovascular outcomes in end-stage renal disease (ESRD) patients. Recent dialysis techniques based on convection, specifically high-efficiency on-line haemodiafiltration (HDF), enhance the removal of middle molecular weight toxins and reduce all-cause mortality in haemodialysis (HD) patients. However, the mechanisms of these improved outcomes remain to be established.

METHODS

This prospective study randomly assigned 42 ESRD patients to switch from high-flux HD to high-efficiency on-line HDF (n=22) or to continue HD (n=20). Brachial artery endothelium-dependent flow-mediated dilatation, central pulse pressure, carotid artery intima-media thickness (IMT), internal diastolic diameter and distensibility and circulating markers of uraemia, inflammation and oxidative stress were blindly assessed before and after a 4-month follow-up.

RESULTS

Brachial flow-mediated dilatation and carotid artery distensibility increased significantly in the HDF group compared with HD, while carotid IMT and diameter remained similar. HDF decreased predialysis levels of the uraemic toxins β2-microglobulin, phosphate and blood TNFα mRNA expression. Oxidative stress markers were not different between the HD and HDF groups. Blood mRNA expression of protein kinase C β2, an endothelial NO-synthase (eNOS) inhibitor, decreased significantly with HDF.

CONCLUSIONS

High-efficiency on-line HDF prevents the endothelial dysfunction and stiffening of the conduit arteries in ESRD patients compared with high-flux HD. HDF decreases uraemic toxins, vascular inflammation, and is associated with subsequent improvement in eNOS functionality. These results suggest that reduced endothelial dysfunction may be an intermediate mechanism explaining the beneficial outcomes associated with HDF.

Reduction of oxidative damage reflects a better kidney transplantation outcome

BACKGROUND/AIMS

DNA fragmentation is one of the typical features of apoptosis, frequently induced by oxidative stress. Increased oxidative stress is known to be related to several pathological processes. In this study, we assessed oxidative damage in the early follow-up period after kidney transplantation measuring DNA oxidation and fragmentation of mononuclear cells and the circulating levels of inflammatory cytokines.

METHODS

Blood samples from 30 kidney transplant recipients were collected before transplantation and after 2 days, 1 month and 6 months. Oxidative DNA fragmentation was measured by Comet Assay, whereas DNA oxidation was evaluated measuring 8-OHdG leukocyte levels. Serum IL-1β, IL-4, IL-6, IL-8, IL-10, IFN-γ and TNF-α were assayed using a multiplex ELISA analysis.

RESULTS

At 6 months after transplantation, a significant reduction in DNA fragmentation and IL-6 plasma levels was observed; DNA oxidation was higher in patients with a worse outcome, with delayed graft function and low nutritional status. We also found a correlation of IL-6 and IL-10 levels with DNA fragmentation and of IL-10 levels with DNA oxidation.

CONCLUSION

Low levels of oxidation and apoptosis at 6 months after transplantation correlate with a better recovery of renal function in kidney allografts. The measurement of cytokine levels confirmed a reduction of inflammatory parameters within 6 months of follow-up.

Renal transplantation normalized hydrogen peroxide production of neutrophils within the first day

BACKGROUND

Hemodialysis patients are in a state of oxidant stress. In renal transplantation reactive oxygen species (ROS) are considered to be important factors of ischemia-reperfusion injury. Neutrophils produce ROS as part of the host defense against invading bacteria. This study was designed to investigate whether neutrophil function in hemodialysis patients is immediately affected by renal transplantation.

METHODS

We evaluated the neutrophil respiratory burst and phagocytic activity in renal transplant patients with living-related donor (LRD) and cadaveric donor (CAD) grafts using flow cytometry techniques. Twenty patients (LRD = 6, CAD = 14) and 20 healthy volunteers were included in the study. Venous blood samples were drawn before anesthesia, 5 min before reperfusion, 1 h and 1, 3 and 7 days after reperfusion.

RESULTS

Before surgery, a significant increase in hydrogen peroxide production in neutrophils was seen for both renal transplantation groups compared to healthy subjects. Within 24 h after reperfusion hydrogen peroxide production almost decreased to normal values. The phagocytic capacity of neutrophils was continuously depressed. There were no differences between the CAD and LRD groups.

CONCLUSIONS

We found that the enhanced respiratory burst activity of patients with chronic renal failure decreased to normal values within 1 day following renal transplantation. Our results suggest that reduced respiratory burst activity resulting in a diminished risk of tissue damage by the uncontrolled production of ROS.

Differential effects of dialysis and ultrafiltrate from individuals with CKD, with or without diabetes, on platelet phosphatidylserine externalization

Individuals with chronic kidney disease (CKD) and/or diabetes mellitus (DM) are at increased risk of cardiovascular events and have elevated externalization of phosphatidylserine (PS; which propagates thrombus formation) in a small subpopulation of platelets. The purpose of this study was to examine the effect of 1) removing uremic toxins by hemodialysis on PS externalization in patients with either CKD or CKD and DM and 2) ultrafiltrate (UF) from these individuals on PS externalization in healthy platelets. PS externalization was quantified by a fluorescence-activated cell sorter using annexin V in platelet-rich plasma. PS externalization was elevated threefold in CKD patients and returned to basal values during 3-h hemodialysis. In contrast, it was elevated fivefold in individuals with CKD and DM and was still threefold above control after 3-h treatment. UF significantly increased PS externalization in a small subpopulation of platelets from healthy controls. The effect of UF from individuals with CKD and DM was significantly greater than that from patients with CKD alone, and the responses were partially inhibited by the protein kinase Cδ (PKCδ) inhibitor rottlerin and the 5-hydroxytryptamine (5-HT)2A/2Creceptor antagonist ritanserin. The data suggest that uremic toxins present in UF mediate PS externalization in a small subpopulation of platelets, at least in part, via the 5-HT2A/2Creceptor and PKCδ and demonstrate that DM further enhances platelet PS externalization in CKD patients undergoing hemodialysis. This may explain, at least in part, the additional increase in vascular damage observed in CKD patients when DM is present.

Early loss of proliferative potential of human peritoneal mesothelial cells in culture: the role of p16INK4a-mediated premature senescence

Much has been learned about the mechanisms underlying cellular senescence. The pathways leading to senescence appear to vary, depending on the cell type and cell culture conditions. In this respect, little is known about senescence of human peritoneal mesothelial cells (HPMC). Previous studies have significantly differed in the reported proliferative lifespan of HPMC. Therefore, in the present study, we have examined how HPMC enter state of senescence under conditions typically used for HPMC culture. HPMC were isolated from omentum and grown into senescence. The cultures were assessed for the growth rate, the presence of senescence markers, activation of cell-cycle inhibitors, and the oxidative stress. HPMC were found to reach, on average, six population doublings before senescence. The terminal growth arrest was associated with decreased expression of Ki67 antigen, increased percentage of cells in the G1 phase, reduced early population doubling level cDNA-1 mRNA expression, and the presence of senescence-associated beta-galactosidase. Compared with early-passage cells, the late-passage HPMC exhibited increased expression of p16INK4a but not of p21Cip1. In addition, these cells generated more reactive oxygen species and displayed increased presence of oxidatively modified DNA (8-hydroxy-2'-deoxyguanosine). These results demonstrate that early onset of senescence in omentum-derived HPMC may be associated with oxidative stress-induced upregulation of p16INK4a.