Oxidative Stress in Patients with End-Stage Renal Disease prior to the Start of Renal Replacement Therapy

Training vs. Tolerance: The Yin/Yang of the Innate Immune System

For almost nearly a century, memory functions have been attributed only to acquired immune cells. Lately, this paradigm has been challenged by an increasing number of studies revealing that innate immune cells are capable of exhibiting memory-like features resulting in increased responsiveness to subsequent challenges, a process known as trained immunity (known also as innate memory). In contrast, the refractory state of endotoxin tolerance has been defined as an immunosuppressive state of myeloid cells portrayed by a significant reduction in the inflammatory capacity. Both training as well tolerance as adaptive features are reported to be accompanied by epigenetic and metabolic alterations occurring in cells. While training conveys proper protection against secondary infections, the induction of endotoxin tolerance promotes repairing mechanisms in the cells. Consequently, the inappropriate induction of these adaptive cues may trigger maladaptive effects, promoting an increased susceptibility to secondary infections—tolerance, or contribute to the progression of the inflammatory disorder—trained immunity. This review aims at the discussion of these opposing manners of innate immune and non-immune cells, describing the molecular, metabolic and epigenetic mechanisms involved and interpreting the clinical implications in various inflammatory pathologies.

Trained immunity - basic concepts and contributions to immunopathology

Trained immunity is a functional state of the innate immune response and is characterized by long-term epigenetic reprogramming of innate immune cells. This concept originated in the field of infectious diseases - training of innate immune cells, such as monocytes, macrophages and/or natural killer cells, by infection or vaccination enhances immune responses against microbial pathogens after restimulation. Although initially reported in circulating monocytes and tissue macrophages (termed peripheral trained immunity), subsequent findings indicate that immune progenitor cells in the bone marrow can also be trained (that is, central trained immunity), which explains the long-term innate immunity-mediated protective effects of vaccination against heterologous infections. Although trained immunity is beneficial against infections, its inappropriate induction by endogenous stimuli can also lead to aberrant inflammation. For example, in systemic lupus erythematosus and systemic sclerosis, trained immunity might contribute to inflammatory activity, which promotes disease progression. In organ transplantation, trained immunity has been associated with acute rejection and suppression of trained immunity prolonged allograft survival. This novel concept provides a better understanding of the involvement of the innate immune response in different pathological conditions, and provides a new framework for the development of therapies and treatment strategies that target epigenetic and metabolic pathways of the innate immune system.

Head-to-Head Comparison of Oxidative Stress Biomarkers for All-Cause Mortality in Hemodialysis Patients

Oxidative stress (OS) presents even in the early chronic kidney disease (CKD) stage and is exacerbated in patients with end-stage renal disease (ESRD) undergoing maintenance hemodialysis (MHD). There is still a debate over the association between oxidative stress and mortality. Our study aims to compare head-to-head the prognostic value of different oxidative markers for all-cause mortality in hemodialysis (HD) patients. We thus enrolled 347 patients on HD in this prospective study. Four OS biomarkers were measured (carbonyl proteins, myeloperoxidase (MPO), advanced oxidation protein products (AOPPs), and oxidized low-density lipoprotein (ox-LDL)). During the 60-month follow-up period, 9 patients have been lost to follow-up and 168 (48.4%) patients died. Concerning the oxidative stress (ox-stress) byproducts, carbonyl proteins were lower in survivors (105.40 ng/mL (IQR 81.30−147.85) versus 129.65 ng/mL (IQR 93.20−180.33); p < 0.001), with similar results for male patients (103.70 ng/mL (IQR 76.90−153.33) versus 134.55 ng/mL (IQR 93.95−178.68); p = 0.0014). However, there are no significant differences in MPO, AOPP, and ox-LDL between the two groups. Kaplan−Meier survival analysis indicated that patients in the higher carbonyl proteins concentration (>117.85 ng/mL group) had a significantly lower survival rate (log-rank test, p < 0.001). Univariate Cox regression analysis showed a positive correlation between carbonyl proteins and all-cause mortality in the higher and lower halves. Even after adjustment for conventional risk factors, it remained a statistically significant predictor of an increased risk of death in MHD. Univariate Cox regression analysis of MPO showed that continuous MPO and Log MPO were significantly associated with all-cause mortality, except for binary MPO (divided according to the median of MPO). Multivariate Cox analysis for MPO showed that the mortality prediction remains significant after adjusting for multiple factors. In conclusion, not all ox-stress biomarkers predict all-cause mortality in HD patients to a similar extent. In the present study, carbonyl proteins and MPO are independent predictors of all-cause mortality in HD patients, whereas AOPPs and oxLDL are clearly not associated with all-cause mortality in HD patients.

Serum LDL Levels are a Major Prognostic Factor for Arteriovenous Fistula Thrombosis (AVFT) in Hemodialysis Patients

Introduction

Arteriovenous fistula thrombosis (AVFT) is still a common cause of morbidity in patients undergoing regular hemodialysis (HD). Many factors have been found to induce AVFT. Some of those factors are local and others are systemic ones. In this study, we evaluated some local and systemic factors simultaneously, to predict the most potent risk factor for AVFT in HD patients.

Patients and methods

One hundred and eighteen patients aged 20–80 yrs with end-stage renal disease (ESRD) were evaluated prospectively for a period of 14 months. First, anticardiolipin antibodies (ACLA), TG, cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) were analyzed by conventional methods. Other basic data were accessed from patients' medical records. All fistulas were evaluated clinically as patent at the start of this study. Patients were followed-up for any evidence of AVFT within 14 months. Finally, all factors (diabetes, hypertension, presence of ACLA, ultrafiltration ≥3 L, age, gender, weight, hypotension during dialysis, fistula site, epoetin alpha usage, TG, HDL, LDL and total cholesterol) were analyzed in a stepwise regression analysis.

Results

Eighteen episodes of AVFT documented with Doppler sonography occurred in 17 patients (15.3%). Regression analysis showed only LDL values were the AVFT predictor in our patients (p=0.002, β-coefficient=0.3). Kaplan-Meier analysis showed a significantly lower AVF patency time in patients with LDL >130 mg/dl than those with LDL <130 mg/dl (log rank=0.0014).

Discussion

LDL value is a major prognostic factor for AVFT in HD patients and lowering it to <130 mg/dl could improve fistula patency.

Increased Levels of sRAGE in Diabetic CKD-G5D Patients: A Potential Protective Mechanism against AGE-Related Upregulation of Fibroblast Growth Factor 23 and Inflammation

Advanced glycation end products (AGEs) may induce cardiac remodeling in kidney disease by promoting fibroblast growth factor 23 (FGF-23) expression. Since AGEs are increased in diabetes mellitus (DM), our first aim was to evaluate the existence of any potential association between AGEs, FGF-23, inflammation, and increased cardiovascular risk in DM patients on dialysis (CKD-G5D). Secondarily, we explored the potential role of the soluble receptor for AGEs (sRAGE) as a marker of heart failure. Levels of glycated albumin (GA), sRAGE, c-terminal FGF-23 (cFGF-23), brain natriuretic peptide (BNP), and inflammatory mediators were compared between DM and non-DM CKD-G5D patients. The levels of sRAGE, cFGF-23, BNP, and proinflammatory markers were over the ranges of normality in both DM and non-DM groups. Only GA and sRAGE levels were increased in DM compared to non-DM patients. Plasma levels of sRAGE and CRP were the only independent predictors of BNP concentration. In conclusion, in DM CKD-G5D patients, sRAGE appeared to be a marker of cardiac remodeling. Indeed, its increase could be a potential protective mechanism against the increased risk of cardiovascular complications related to AGEs and inflammation. The causal relationship between sRAGE and cardiovascular risk in these patients needs to be further confirmed by mechanistic studies.

Association of Plasma Adiponectin and Oxidized Low-Density Lipoprotein with Carotid Intima-Media Thickness in Diabetic Nephropathy

AIMS

We sought to determine the association between levels of adiponectin and oxidized low-density lipoprotein (ox-LDL) in patients with diabetic nephropathy as well as their effect on carotid intima-media thickness (cIMT).

METHODS

Adiponectin and ox-LDL were determined in 25 diabetic patients without nephropathy and 94 patients at different stages of diabetic nephropathy including subjects on hemodialysis. cIMT was measured using real-time B-mode ultrasonography.

RESULTS

Plasma adiponectin levels increased significantly with severity of diabetic nephropathy (P = 0.002), on the contrary to ox-LDL which decreased with disease severity (P < 0.001). cIMT was significantly higher at late stages of diabetic nephropathy compared with early stages (P = 0.022). Adiponectin was a significant negative predictor of ox-LDL levels (β = -5.45, P = 0.023), independently of confounding factors. There was no significant correlation between cIMT and adiponectin or ox-LDL either in the total sample population or according to disease staging. Cluster analysis showed that patients with the highest cIMT values, highest levels of adiponectin, and lowest levels of ox-LDL were included in one cluster and all assigned to stage 5 of diabetic nephropathy.

CONCLUSIONS

There was no significant association between adiponectin or ox-LDL and cIMT and, therefore, other factors affecting this surrogate marker of cardiovascular disease in diabetic nephropathy should be sought.

Oxidative stress in patients with cardiovascular disease and chronic renal failure

Oxidative response regulates many physiological response in human health, but if not properly regulated it could also lead to a number of deleterious effects. The importance of oxidative stress injury depends on the molecular target, the severity of the stress, and the mechanism by which the oxidative stress is imposed: it has been implicated in several diseases including cancer, neurodegenerative diseases, malaria, rheumatoid arthritis and cardiovascular and kidney disease. Most of the common diseases, such as hypertension, atherosclerosis, heart failure, and renal dysfunction, are associated with vascular functional and structural alterations including endothelial dysfunction, altered contractility, and vascular remodeling. Common to these processes is increased bioavailability of reactive oxygen species (ROS), decreased nitric oxide (NO) levels, and reduced antioxidant capacity. Oxidative processes are up-regulated also in patients with chronic renal failure (CRF) and seem to be a cause of elevated risk of morbidity and mortality in these patients. In this review, we highlight the role of oxidative stress in cardiovascular and renal disease.

FGF23 associated bone diseases

Recently, fibroblast growth factor 23 (FGF23) has sparked widespread interest because of its potential role in regulating phosphate and vitamin D metabolism. In this review, we summarized the FGF superfamily, the mechanism of FGF23 on phosphate and vitamin D metabolism, and the FGF23 related bone disease.

Oxidized low-density lipoprotein (oxLDL) plasma levels and oxLDL to LDL ratio - are they real oxidative stress markers in dialyzed patients?

AIMS

Dyslipidemia and oxidative stress are commonly present in patients during maintenance dialysis treatment. However, the significance of oxidized LDL (oxLDL) as a marker of oxidative stress in uremia is still unresolved. The aim of this study was to establish the role of oxLDL and oxLDL/LDL ratio as markers of lipoprotein abnormalities and oxidative stress in the dialyzed patients.

MAIN METHODS

Plasma oxLDL level was measured by ELISA, and oxLDL/LDL ratio was calculated in 106 dialyzed patients and 20 controls. The linkages between oxLDL, oxLDL/LDL ratio and lipid profile and oxidative stress markers malondialdehyde (MDA) and Cu/Zn superoxide dismutase (Cu/Zn SOD) levels were also analyzed.

KEY FINDINGS

OxLDL levels and oxLDL/LDL ratio were similar in hemodialyzed patients and controls, whereas these parameters were lower in peritoneally dialyzed patients when compared to healthy individuals. In contrast, both MDA and Cu/Zn SOD levels were significantly higher in uremics than in controls. oxLDL and oxLDL/LDL ratio positively correlated with lipid profile (except of HDL), whereas there were no positive associations between these parameters and both MDA and Cu/Zn SOD. Multiple regression analysis confirmed that increased oxLDL/HDL and TC/HDL ratios and total cholesterol levels are the parameters which independently predicted oxLDL in dialyzed patients. In the case of oxLDL/LDL ratio, the independent variables were oxLDL/HDL ratio, total cholesterol and HDL levels.

SIGNIFICANCE

oxLDL levels and oxLDL/LDL ratio seem to be the markers of lipoprotein abnormalities rather than the markers of oxidative stress in the population of dialyzed patients.

Dietary antioxidents and oxidative stress in predialysis chronic kidney disease patients

CONTEXT

Dietary antioxidants are important in protecting against human diseases. Oxidative stress, a non- traditional risk factors of cardio-vascular disease is far more prevalent in chronic kidney disease (CKD) patients than in normal subjects.

EVIDENCE ACQUISITIONS

Directory of Open Access Journals (DOAJ), Google Scholar, Pubmed (NLM), LISTA (EBSCO) and Web of Science have been searched.

RESULTS

Oxidative stress could be a consequence of an increase in reactive oxygen species as well as a decrease in antioxidant defenses. Among the important factors that can be involved in triggering oxidative stress is insufficient dietary intake of antioxidants. Malnourished CKD patients are reported to have more oxidative stress than well nourished ones.

CONCLUSIONS

Moving beyond the importance of assessment of dietary protein and energy in pre dialysis CKD patients to the assessment of dietary antioxidants is of utmost importance to help combat enhanced oxidative stress levels in such patients.

Skin autofluorescence: a pronounced marker of mortality in hemodialysis patients

Background

Accelerated formation and tissue accumulation of advanced glycation endproducts (AGEs), reflecting cumulative glycemic and oxidative stress, occur in age-related and chronic diseases like diabetes mellitus (DM) and renal failure, and contribute to vascular damage. Skin autofluorescence (AF), a noninvasive measurement method, reflects tissue accumulation of AGEs. The aim of our study was to determine the predictive value of skin AF on overall and cardiovascular mortality in hemodialysis patients.

Methods

Baseline skin AF was measured in 105 patients on hemodialysis, 23 had DM. Survival status was assessed after a mean follow-up period of 4.9 years (interquartile range 2.3–6.9 years).

Results

Multivariate Cox regression analysis showed skin AF (hazard ratio (HR) 1.83; 95% confidence interval (CI) 1.32–2.54), preexisting cardiovascular disease (CVD) (HR 2.77; 95% CI 1.48–5.18), renal replacement therapy duration (HR 1.10; 95% CI 1.01–1.19), age (HR 1.03; 95% CI 1.01–1.06), serum albumin (HR 0.90; 95% CI 0.85–0.95), hematocrit (HR 0.92; 95% CI 0.86–0.98), phosphorus (HR 2.01; 95% CI 1.15–3.49), and parathyroid hormone (HR 0.99; 95% CI 0.98–0.996) to be predictors of mortality, whereas DM was not. Preexisting CVD and serum phosphorus were the only predictors of cardiovascular mortality.

Conclusion

Skin AF showed to be an independent predictor of overall mortality in hemodialysis patients, but it had no predictive value for cardiovascular mortality.

Cardiovascular Complications in CKD Patients: Role of Oxidative Stress

Starting with the early stages, patients with chronic kidney disease (CKD) experience higher burden of cardiovascular disease (CVD). Moreover, CVD complications are the major cause of mortality in CKD patients as compared with complications from chronic kidney failure. While traditional CVD risk factors, including diabetes, hypertension, hyperlipidemia, obesity, physical inactivity, may be more prevalent among CKD patients, these factors seem to underestimate the accelerated cardiovascular disease in the CKD population. Search for additional biomarkers that could explain the enhanced CVD risk in CKD patients has gained increasing importance. Although it is unlikely that any single nontraditional risk factor would fully account for the increased CVD risk in individuals with CKD, oxidative stress appears to play a central role in the development and progression of CVD and its complications. We will review the data that support the contribution of oxidative stress in the pathogenesis of CVD in patients with chronic kidney failure.

AGEs/RAGE in CKD: irreversible metabolic memory road toward CVD?

BACKGROUND

Cardiovascular disease is the major cause of death in patients with renal insufficiency, accounting for 50% of all deaths in renal replacement therapy patients. Mortality from cardiovascular diseases in these patients is approximately 9% per year, which is about 30 times the risk in the general population. So far, intensive interventions to the general risk factors, such as high LDL-cholesterol or C-reactive protein, have not been successful in improving their cardiovascular outcomes, suggesting that the beneficial effect of risk reduction may be overwhelmed by accumulated risk memorized by long-term exposure to oxidative stress during the progression of renal failure.

DESIGN

In this review, we propose that this irreversible memory effect in renal failure may be mediated by advanced glycation end-products (AGEs).

RESULTS

The generation of AGEs has been implicated to be deeply associated with increased oxidative stress. Moreover, interaction of the receptor for AGEs (RAGE) with AGEs leads to crucial biomedical pathway generating intracellular oxidative stress and inflammatory mediators, which could result in further amplification of the pathway involved in AGE generation. Several lines of evidence suggest that AGEs/RAGE axis can profoundly be involved in cardiovascular diseases. Recent advances in AGEs and RAGE measurements led us to be capable of understanding more about the role of AGEs/RAGE axis as a risk for cardiovascular diseases in patients with renal failure.

CONCLUSION

AGEs/RAGE axis could be a crucial mediator of oxidative stress in renal failure. RAGE could be not only a useful biomarker, but also a potentially therapeutic target to overcome the accumulated adverse metabolic memory in renal failure.

Low-density lipoprotein oxidizability in children with chronic renal failure

BACKGROUND

In childhood, dyslipidemia and low-density lipoprotein (LDL) oxidation play an important role in the development of atherosclerosis. Alterations of these factors have been shown in adult uremic patients.

METHODS

Nine children affected by chronic renal failure (CRF; urinary tract malformation, n = 8; polycystic kidney disease, n = 1) were studied to investigate the abnormalities of plasma lipoprotein concentration and composition and to assess the susceptibility of LDL to oxidation. All patients with CRF were on conservative treatment and, after informed consent, underwent the evaluation of (i) quantitative and qualitative plasma lipid profile; (ii) lipoprotein oxidation in vitro; and (iii) lipoprotein anti-oxidant content. These results were compared to those of an age-matched control group of eight healthy children.

RESULTS

Total cholesterol, LDL and triglycerides were significantly higher in CRF than in the control group. The composition of lipoproteins was different in the two groups: the amount of anti-oxidant factors (alpha-, gamma-tocopherol and carotenoids) was different in CRF and normal controls children, while LDL susceptibility to oxidation was significantly higher in uremic children than in controls.

CONCLUSIONS

CRF patients, already before dialysis, have a higher LDL oxidizability due to an altered lipoprotein composition and a low anti-oxidant content; therefore they have higher risk factors for atherosclerosis. On the basis of these data, supplementation with anti-oxidants might be useful in CRF children, but further studies are needed to evaluate the efficacy and safety of this therapeutic intervention.

Alteration of serum semicarbazide-sensitive amine oxidase activity in chronic renal failure

Despite recent intensive investigations, physiological and pathological role of semicarbazide-sensitive amine oxidase (SSAO) is far from clear. In this study, serum SSAO activity was determined, radiochemically, in various groups of uremic patients: haemodialysed (HD), peritoneally dialysed (PD) and those receiving conservative treatment but still not dialysed (ND), as well as in controls. Reduced enzyme activity was found in HD uremic patients before and after dialysis treatment, compared to controls (5260 +/- 862 and 6011 +/- 958 pmol/h/ml vs. 8601 +/- 283 pmol/h/ml, p < 0.01 and p < 0.05, respectively). The activity was slightly lower in PD, and normal in ND patients. In HD patients SSAO activity was also determined by an assay based on the formation of hydrogen peroxide, and was found to be elevated compared to controls (2384 +/- 323 pmol/h/ml vs. 1437 +/- 72 pmol/h/ml, p < 0.05). The elevated serum SSAO activity measured through the detection of the enzyme-generated hydrogen peroxide in HD patients might indicate its contribution to the accelerated atherosclerotic disease observed in uremia.

Chronic renal failure-induced multiple-organ injury in rats is alleviated by the selective CysLT1 receptor antagonist montelukast

Chronic renal failure (CRF) is associated with oxidative stress that promotes production of reactive oxygen species and cytokine release. We aimed to investigate the possible protective effect of montelukast, a CysLT1 receptor antagonist, against oxidative damage in a rat model of CRF, induced by 5/6 reduction of renal mass. Male Wistar albino rats were randomly assigned to either the CRF group or the sham-operated control group, which received saline or montelukast (10mg/kg, i.p.) for 4 weeks. At the end of the 4 weeks, rats were decapitated and trunk blood was collected. Creatinine, blood urea nitrogen and lactate dehydrogenase (LDH) activity were measured in the serum samples, while leukotriene B(4), TNF-alpha, IL-1 beta, IL-6, total antioxidant capacity (AOC) and leukocyte apoptosis were assayed in plasma samples. Kidney, lung, heart and brain tissue samples were taken for the determination of tissue malondialdehyde (MDA), glutathione (GSH) levels, and myeloperoxidase (MPO) activity. Oxidant-induced tissue fibrosis was determined by tissue collagen contents, and the extent of tissue injuries was analyzed microscopically. CRF caused significant decreases in tissue GSH and plasma AOC, which were accompanied with significant increases in MDA levels, MPO activities, and collagen contents of all the studied tissues, while the circulating levels of the pro-inflammatory mediators, LDH activity, creatinine and BUN were elevated. Montelukast treatment reversed all these biochemical indices, as well as histopathological alterations induced by CRF. Similarly, flow cytometric measurements revealed that leukocyte apoptosis was increased in CRF group, while montelukast reversed this effect. In conclusion, CRF-induced oxidative tissue injury occurs via the activation of pro-inflammatory mediators and by neutrophil infiltration into tissues, and that protective effects of montelukast on CRF-induced injury can be attributed to its ability to inhibit neutrophil infiltration and apoptosis, to balance oxidant-antioxidant status and to regulate the generation of pro-inflammatory mediators.

Impaired renal function and duration of dialysis therapy are associated with oxidative stress and proatherogenic cytokine levels in patients with end-stage renal disease

OBJECTIVES

The present study was undertaken to clarify the role of the impaired renal function and the dialysis therapy on plasma levels of proatherogenic cytokines and Cu/Zn superoxide dismutase (Cu/Zn SOD)--as a marker of oxidative stress (SOX) in uraemia.

DESIGN AND METHODS

We have measured the levels of Cu/Zn SOD, monocyte chemoattractant protein-1 (MCP-1) macrophage inflammatory proteins (MIP-1alpha, MIP-1beta) and vascular endothelial growth factor (VEGF) in the plasma of predialysis (CRF) (n=42), on maintenance hemodialysis (HD) (n=25) or peritoneal dialysis (PD) (n=45) patients and in the healthy volunteers (n=20).

RESULTS

The increase in Cu/Zn SOD levels was in PD and HD patients compared to controls (215.56+/-125.18 and 356.28+/-122.57 versus 53.53+/-23.65 ng/ml, respectively). In plasma of the CRF, PD and HD subjects we have also observed the significant increase in the levels of MIP-1beta: [31.5 (2-149), 33.0 (1-203) and 76.0 (9-345), respectively]; MCP-1 (616.50+/-240.15, 943.64+/-348.99 and 968.50+/-355.85, respectively) and VEGF (387.93+/-184.63, 371.56+/-125.18 and 645.56+/-136.30, respectively) compared to healthy people. In the predialysis group, creatinine clearance correlated with Cu/Zn SOD and cytokine levels. Moreover, the cytokine levels were also associated with age. In dialysis patients, the correlations were between duration of dialysis treatment and both Cu/Zn SOD and cytokine levels. There was also a direct relationship between Cu/Zn SOD and both MIP-1beta and VEGF levels.

CONCLUSIONS

This study has shown that impaired renal function, age and duration of dialysis treatment are associated with increased oxidative stress and proatherogenic cytokine levels in uremic patients.

Inflammation but not oxidative stress is associated with beta-chemokine levels and prevalence of cardiovascular disease in uraemic patients

Inflammation and oxidative stress (SOX) have been reported in patients with chronic renal failure (CRF), but their influence on beta-chemokines levels and cardiovascular disease (CVD) prevalence remains unknown. We assessed beta-chemokines, SOX markers and high sensitivity C-reactive protein (hs CRP) as a marker of inflammation in 40 uraemic patients, both with as well as without CVD and 20 controls. Compared with the controls, the patients with CVD showed a significant increase in plasma concentrations of monocyte chemoattractant protein-1 (MCP-1), total peroxide (both p<0.05), macrophage inflammatory protein 1beta (MIP-1beta) and hs CRP (both p<0.01). The values of MCP-1 and hs CRP were more elevated in patients with CVD than without CVD (p<0.01 and p<0.05; respectively). Both subgroup of CRF patients were lower of regulated upon activation, normal T cell expressed and secreted (RANTES) levels than in the controls (both p<0.001). The positive relationships were between hs CRP and presence of CVD, MIP-1beta (both p<0.01) and MCP-1 levels (p<0.05). SOX markers did not show any significant correlation with beta-chemokines, hs CRP and presence of CVD. We documented that increased inflammation but not SOX were associated with significant elevation in plasma beta-chemokines levels and CVD prevalence in CRF patients not requiring dialysis.

Oxidative stress, inflammation and early cardiovascular damage in children with chronic renal failure

The relationship between inflammation, oxidant stress and cardiovascular damage in children with chronic renal failure (CRF) has not previously been investigated. The aim of this study was to investigate markers of oxidative stress, inflammation and early cardiovascular abnormalities. Therefore, erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities; blood glutathione (GSH) and serum malondialdehyde (MDA) levels; C-reactive protein (CRP) and proinflammatory cytokines (IL-6, TNF-alpha,); and left ventricular masses (LVM) and intima media thicknesses (IMT) were measured in children with CRF. A total of 29 children with CRF (19 nondialysis, 10 peritoneal dialysis) were included. The control group consisted of 25 healthy subjects. CRF children had significantly increased IL-6, TNF-alpha, CRP and MDA concentrations and decreased SOD, CAT and GSH levels compared with controls (P<0.05). Nondialysis and peritoneal dialysis subgroups had similar oxidative stress and inflammation biomarkers (P>0.05). Erythrocyte CAT was positively correlated with CRP, TNF-alpha, and IL2-R in the study group. Positive correlations were found between cytokine concentrations, CRP and urea/creatinine levels. Significantly increased LVM and IMT values were found in CRF children (P<0.05). In conclusion, increased oxidant stress and inflammation together with early cardiovascular damage were found in CRF children. Further studies with more patients are needed to verify these results.

Paraoxonase, anti-oxidant response and oxidative stress in children with chronic renal failure

Increased oxidative stress is believed to contribute to an increased risk of cardiovascular disease in uraemia. In children with chronic renal failure (CRF), an anti-oxidant enzyme, paraoxonase (PON), that inhibits oxidation of LDL-cholesterol, has not been previously investigated. In this study we aimed to investigate PON activity, total anti-oxidant response (TAR), total peroxide (TPX), oxidative stress index (OSI) and some pro-oxidant cytokines in 29 children with CRF [mean age 10.2+/-3.5 years; 19 pre-dialysis, ten on continuous ambulatory peritoneal dialysis (CAPD)] and in 25 control subjects. Children with CRF had lower PON and TAR and higher TPX and OSI values than did controls (P<0.05). Except for lower TAR and serum albumin levels of the CAPD subgroup (P<0.05), other parameters were similar in non-dialysis and CAPD patients (P>0.05). Patients had significant positive correlation between TAR and serum albumin (P<0.05). Serum urea had significant positive correlation with TPX and OSI (P<0.05). Increased oxidative stress and decreased anti-oxidants measured by serum PON activity and TAR were found in children with CRF. We can hypothesize, on the basis of statistical correlations, that low levels of serum albumin and high levels of uraemic metabolites might be responsible for increased oxidative stress in children with CRF. Further studies with larger sample sizes are needed to verify these results.

The effect of the initiation of renal replacement therapy on lipid profile and oxidative stress during the first 6 months of treatment

BACKGROUND

Disturbed lipoproteins and increased oxidative stress are two of the "non-traditional" cardiovascular risk factors in chronic renal failure. There are very few prospective data of the influence of dialysis on these two factors. In the present study we investigated the effects of the initiation of both hemo- and peritoneal dialysis therapy on lipoproteins and parameters of LDL oxidation.

METHODS

In this prospective cohort study, we assessed lipoproteins, plasma lipid peroxides and in vitro copper-induced LDL oxidation in 46 patients with end-stage renal disease prior to the start of dialysis and after 6 months of treatment with either hemodialysis (n=33) or peritoneal dialysis (n=13).

RESULTS

After 6 months of treatment with hemodialysis there was an increase in total cholesterol (4.6+/-1.1 vs. 5.0+/-1.3 mmol/l; p<0.05) and triglycerides (2.0+/-0.9 vs. 2.8+/-1.6 mmol/l; p<0.03). In the peritoneal dialysis group the lipoproteins did not change. Regarding lipid peroxides and in vitro copper-induced LDL oxidation, also no changes were observed after 6 months of treatment in both groups.

CONCLUSION

Dyslipidemia aggravates after 6 months of hemodialysis but not after 6 months of peritoneal dialysis. During this period, no net effects on oxidative stress were demonstrated.

Cellular oxidative processes in relation to renal disease

This article summarizes the biochemical processes that produce reactive oxygen species (ROS) and other mediators that account for 'oxidative stress'. Formation of ROS in signal transduction cascades is illustrated from studies of kidney cell systems. The pathophysiological implications for the nephrologist are then reviewed.