Serum sulfatide abnormality is associated with increased oxidative stress in hemodialysis patients

Sulfatides are major glycosphingolipids of lipoproteins that influence atherosclerosis and blood coagulation. Our previous cross‐sectional study of hemodialysis patients showed that serum sulfatide levels decreased markedly with increasing duration of hemodialysis treatment, which may contribute to the development of cardiovascular disease. However, this past study could not demonstrate the time‐dependent change in serum sulfatide levels in each patient, and the underlying mechanism is unknown. To confirm the time‐dependent aggravation of serum sulfatide abnormality, 95 stable hemodialysis outpatients were followed up for 3 years. To show the underlying mechanisms, we statistically analyzed correlations between serum sulfatide levels and clinical factors, including an oxidative stress marker, malondialdehyde. Serum sulfatides were quantified by mass spectrometry after conversion to lysosulfatides. Malondialdehyde was measured using a colorimetric assay. The results showed a time‐dependent decrease in serum sulfatide levels associated with increased malondialdehyde levels, although the absolute level of serum malondialdehyde does not determine the baseline level of serum sulfatides. Multiple linear regression analysis showed a significant correlation only between the time‐dependent change in serum sulfatide levels and the time‐dependent change in serum malondialdehyde levels. This study demonstrated, for the first time, a time‐dependent aggravation of serum sulfatide abnormality in hemodialysis patients, as well as the potential relationship between serum sulfatide abnormality and increasing oxidative stress. These findings suggest that oxidative stress might be an aggravating factor in serum sulfatide abnormality. As continuation of hemodialysis treatment hardly improves abnormal serum sulfatide levels or increased oxidative stress, development of novel therapeutic strategies may be important.     

Silica nanoparticle induces oxidative stress and provokes inflammation in human lung cells

Amorphous silica has been used in a wide variety of industrial and consumer applications. Nanosized silica is being considered a potentially ideal nanomaterial for biomedical and biotechnological applications. In the present study, hierarchical oxidative stress paradigms of nanoparticle toxicity were assumed to evaluate the toxicity of amorphous silica nanoparticle in human healthy lung cells, L-132. The cells were exposed to varied concentrations viz. 0, 100, 200, 300, 400 and 500 μg/ml of silica nanoparticle for 24 h. Different parameters of cytotoxicity, oxidative stress and pro-inflammatory markers were assessed. Silica nanoparticle exposure showed concentration-dependent decrease in cell viability, increase in reactive oxygen species with depletion of antioxidant enzyme activity, induction of inteleukin-8 and cyclooxygenase-2 expression and subsequent DNA damage in L-132 cells. The results indicated that amorphous silica nanoparticle followed hierarchical oxidative stress model and generated oxidative stress which provoked the pro-inflammatory response and caused necrosis in human lung cells.     

Effects of l‐carnitine supplement on serum inflammatory cytokines,C‐reactive protein,lipoprotein (a), and oxidative stress in hemodialysis patients with Lp (a) hyperlipoproteinemia

Inflammation, oxidative stress, and high concentration of serum lipoprotein (a) [Lp (a)] are common complications in hemodialysis patients. The present study was designed to investigate the effects of l ‐carnitine supplement on serum inflammatory cytokines, C‐reactive protein (CRP), Lp (a), and oxidative stress in hemodialysis patients with Lp (a) hyperlipoproteinemia [hyper Lp (a)]. This was an unblinded, randomized clinical trial. Thirty‐six hyper Lp (a) hemodialysis patients (23 men and 13 women) were randomly assigned to either a carnitine or control group. Patients in the carnitine group received 1000 mg/d oral l ‐carnitine for 12 weeks, whereas patients in the control group did not receive any l ‐carnitine supplement. At baseline and the end of week 12, 5 mL of blood were collected after a 12‐ to 14‐hours fast and serum free carnitine, CRP, interleukin‐1β, interleukin‐6 (IL‐6), tumor necrosis factor‐α, Lp (a), and oxidized low‐density lipoprotein were measured. Serum free carnitine concentration increased significantly by 86% in the carnitine group at the end of week 12 compared with baseline (P<0.001), while serum CRP and IL‐6 showed a significant decrease of 29% (P<0.05) and 61% (P<0.001), respectively. No significant changes were observed in serum free carnitine, CRP, and IL‐6 in the control group. There were no significant differences between the two groups in mean changes of serum interleukin‐1β, tumor necrosis factor‐α, Lp (a), and oxidized low‐density lipoprotein concentrations. l ‐carnitine supplement reduces inflammation in hemodialysis patients, but has no effect on hyper Lp (a) and oxidative stress.     

Impact of inflammation on anti‐oxidative effects of vitamin E‐coated membrane dialyzer in patients on chronic hemodialysis

Hemodialysis (HD) with the use of vitamin E‐coated membrane (VEM) dialyzers is shown to exert anti‐inflammatory and antioxidative effects in patients with end‐stage renal disease on HD. However, the association of baseline inflammatory status with the antioxidative effects of VEM has not been investigated thus far. Thirty‐five stable end‐stage renal disease patients treated with VEM for 6 months were enrolled in the present prospective, observational cohort study. For the previous 3 months minimum, 17 (48%) patients were dialyzed with a cellulose, eight (23%) patients with a hemophane, and 10 (29%) patients with a polysulfone 1.2 to 1.5 m² hollow fiber dialyzer. The effects of treatment on oxidized low‐density lipoprotein (oxLDL) were stratified according to half percentiles of baseline serum logC‐reactive protein and interleukin‐6, and the association between treatment goal, arbitrarily defined as a minimum 30% decrease in baseline oxLDL, was assessed with the use of logistic regression analysis. The higher C‐reactive protein and interleukin‐6 half percentiles were independently and additively associated with a higher odds ratio for achieving treatment goal. Adjustment for baseline oxLDL, age, sex, HD duration, smoking, and body mass index did not attenuate the odds ratios, whereas the history of diabetes, as primary renal disease, significantly decreased the odds ratio for achieving treatment goal. Increased baseline C‐reactive protein and interleukin‐6 are independent, additive factors associated with the effect of VEM on oxLDL in HD patients.     

Overproduction of reactive oxygen species in end-stage renal disease patients: a potential component of hemodialysis-associated inflammation

During the past decade, hemodialysis (HD)-induced inflammation has been linked to the development of long-term morbidity in end-stage renal disease (ESRD) patients on regular renal replacement therapy. Because interleukins and anaphylatoxins produced during HD sessions are potent activators for nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, an example of an enzyme that is responsible for overproduction of reactive oxygen species (ROS), this may constitute a link between leukocyte activation and cell or organ toxicity. Oxidative stress, which results from an imbalance between oxidant production and antioxidant defense mechanisms, has been documented in ESRD patients using lipid and/or protein oxidative markers. Characterization of HD-induced oxidative stress has included identification of potential activators for NADPH oxidase. Uremia per se could prime phagocyte oxidative burst. HD, far from improving the oxidative status, results in an enhancement of ROS owing to hemoincompatibility of the dialysis system, hemoreactivity of the membrane, and trace amounts of endotoxins in the dialysate. In addition, the HD process is associated with an impairment in antioxidant mechanisms. The resulting oxidative stress has been implicated in long-term complications including anemia, amyloidosis, accelerated atherosclerosis, and malnutrition. Prevention of oxidative stress in HD might focus on improving the hemocompatibility of the dialysis system, supplementation of deficient patients with antioxidants, and modulation of NADPH oxidase by pharmacologic approaches.     

Effect of phosphate binders on oxidative stress and inflammation markers in hemodialysis patients

It has been suggested that phosphate binders may reduce the inflammatory state of hemodialysis (HD) patients. However, it is not clear whether it has any effect on oxidative stress. The objective of this study was to evaluate the effect of sevelamer hydrochloride (SH) and calcium acetate (CA) on oxidative stress and inflammation markers in HD patients. Hemodialysis patients were randomly assigned to therapy with SH (n=17) or CA (n=14) for 1 year. Before the initiation of therapy (baseline) and at 12 months, we measured in vitro reactive oxygen species (ROS) production by stimulated and unstimulated polymorphonuclear neutrophils and serum levels of tumor necrosis factor α, interleukin-10, C-reactive protein, and albumin. There was a significant reduction of spontaneous ROS production in both groups after 12 months of therapy. There was a significant decrease of Staphylococcus aureus stimulated ROS production in the SH group. There was a significant increase in albumin serum levels only in the SH group. In the SH group, there was also a decrease in the serum levels of tumor necrosis factor α and C-reactive protein. Our results suggest that compared with CA treatment, SH may lead to a reduction in oxidative stress and inflammation. Therefore, it is possible that phosphate binders exert pleiotropic effects on oxidative stress and inflammation, which could contribute toward decreasing endothelial injury in patients in HD.     

Pruritus in hemodialysis patients: The problem remains

Pruritus is still one of the most common and disturbing symptoms of end-stage renal disease. The objective of this study is to analyze the prevalence of pruritus in hemodialysis patients and the possible factors implicated in its genesis. In a cross-sectional study, 101 patients on hemodialysis at our center were screened for pruritus. The relationship of various factors with pruritus was evaluated. Of the 101 patients included, 31(30.7%) had pruritus at the time of examination. Patients with pruritus were significantly older than those without pruritus (P=0.0027). Pruritus tended to be more prevalent in patients undergoing dialysis 3 times a week than in those undergoing daily dialysis, but the difference did not reach statistical significance (P=0.0854). Lower transferrin saturation levels were found in patients with pruritus than in those without pruritus (P=0.0144). C-reactive protein levels were significantly higher in patients with pruritus than in those without pruritus (P=0.0013). There was no significant difference between the groups in the levels of the other inflammatory biomarkers measured. However, there was a tendency toward a correlation between the levels of α-1-glycoprotein and the intensity of pruritus (P=0.0834). Our results suggest a possible relationship of the inflammatory response upregulation to pruritus. Additionally, there was a positive relationship between pruritus and iron deficiency, possibly associated with inflammatory elevation of hepcidin. A better understanding of the factors implicated in the genesis of pruritus related to end-stage renal disease is crucial in the development of more effective treatments for this symptom.     

Effect of protein-energy malnutrition on erythropoietin requirement in maintenance hemodialysis patients

Possible interactions between inflammatory and nutritional markers and their impact on recombinant human erythropoietin (rHuEPO) hyporesponsiveness are not well understood. We investigated the role of nutritional status in rHuEPO requirement in maintenance hemodialysis (MHD) patients without evidence of inflammation. This cross-sectional study included 88 MHD patients. The associations between required rHuEPO dose and malnutrition-inflammation score (MIS) and several laboratory values known to be related to nutrition and/or inflammation were analyzed. Anthropometric measures including body mass index, triceps skinfold thickness, and midarm circumferences were also measured. Twenty-three patients with serum C-reactive protein levels >10 mg/L were excluded from the analysis. The remaining 65 patients (male/female, 41/24; age 49.1+/-11.4 years; dialysis duration 99.7+/-63.0 months) were studied. These patients had moderate malnutrition and the average MIS was 7.4 (range 3-17). The average weekly dose of administered rHuEPO was 69.1+/-63.1 U/kg. Malnutrition-inflammation score had a positive correlation with the serum concentration of tumor necrosis factor-alpha, whereas it had a negative correlation with anthropometric measures, total iron-binding capacity, prealbumin, phosphorus, creatinine, and triglyceride. According to Pearson's correlation analysis, significant relationships of increased MIS with increased required rHuEPO dose and rHuEPO responsiveness index (EPO divided by hematocrit) were observed (p=0.008, r=-0.326; p=0.017, r=-0.306, respectively). Recombinant human erythropoietin dose requirement is correlated with MIS and adverse nutritional status in MHD patients without evidence of inflammation. Further research should focus on reversing the undergoing microinflammation for a better outcome in dialysis patients.     

The level of C‐reactive protein in chronic hemodialysis patients: A comparative study between patients with noninfected catheters and arteriovenous fistula in two large Gulf hemodialysis centers

Hemodialysis (HD) patients have greater morbidity and mortality when they have a central venous catheter (CVC) rather than an arteriovenous fistula (AVF) access. Inflammation associated with dialysis catheter use and resultant higher C‐reactive protein (CRP) levels could have an independent adverse effect on patient outcomes. In this prospective study, we investigated whether HD catheters induce inflammation independent of infection. We compared the mean levels of the inflammatory marker (CRP) in 67 patients on maintenance HD using noninfected catheters with 86 HD patients using AVFs at Prince Salman Center for Kidney Diseases, Saudi Arabia (KSA), and Jahra Hospital, Kuwait, who met our inclusion criteria. C‐reactive protein levels were measured every 2 months over a period of 6 months using immunoturbidimetric assay. One hundred fifty‐three patients on maintenance HD for more than 6 months were included in the study, with mean age of 52.19 ± 16.06 years; 66% were males and 34% were females. Serial levels of mean CRP were statistically and significantly higher in group with noninfected catheters (1.33, 1.24, and 1.10 mg/dL) compared to those with AVFs (0.65, 0.59, and 0.68 mg/dL) with P value of 0.000. In our study, we found no relation between CRP level and age, sex, hemoglobin, albumin, calcium, phosphorus, and iPTH level in both groups. Hemodialysis patients with a catheter have a heightened state of inflammation independent of infection, and thus our study supports the avoidance of catheters and a timely conversion to AVFs with catheter removal.     

Effect of a hydrogen (H2)‐enriched solution on the albumin redox of hemodialysis patients

Elevated oxidative stress (OS) is associated with severe cardiovascular disease and premature death among patients treated with hemodialysis (HD). Oxidative stress is enhanced by contact between blood and dialysis membranes during HD sessions. This study aimed to clarify whether hydrogen (H₂), which is a known antioxidant, is capable of suppressing increased OS induced during HD sessions. Eight patients on regular HD treatment were studied. Two HD sessions were performed in a cross‐over design trial using standard and hydrogen‐enriched solutions (mean of 50 p.p.b. H₂; H₂‐HD). Blood samples were obtained from the inlet and outlet of the dialyzer during HD to determine changes in plasma levels of glutathione, hydrogen peroxide, and albumin redox state as a marker of OS. Comparison of inlet and outlet blood revealed significant decreases in total glutathione and reduced glutathione, as well as significant increases in hydrogen peroxide in both HD treatments. However, the mean proportion of reversibly oxidized albumin in outlet serum was significantly lower than that in inlet serum following the H₂‐HD session, whereas no significant changes were found in the standard solution session, suggesting that “intra‐dialyzer” OS is reduced by H₂‐HD. In conclusion, the application of H₂‐enriched solutions could ameliorate OS during HD.     

Increased leukocyte aggregates are associated with atherosclerosis in patients with hemodialysis

Little data are available on the role of blood rheology in atherosclerosis in hemodialysis (HD) patients. This study sought to assess the relationship between leukocytes conjugated with platelets (leukocyte aggregates [LA]) and atherosclerosis in patients with HD. The present study included 118 patients on HD. As surrogate markers of atherosclerosis, aortic stiffness measured by brachial-ankle pulse wave velocity, and carotid intima-media thickness (IMT) were measured. As an assessment of LA, a method, microchannel array flow analyzer, which makes it possible to directly observe the flow of blood cell elements through the microchannel, was used. We measured a number of LA during 50 μL flow of whole blood through microchannels. In 12 age-matched healthy individuals, a number of LA during 50 μL flow of whole blood was 25.7±5.4, whereas in HD patients it was significantly increased up to 48.2±16.4 (P<0.001). Flow cytometry demonstrated that LA were predominantly monocytes. Leukocyte aggregates were positively associated with plasma levels of fibrinogen (P<0.01), or serum high-sensitive C-reactive protein (P<0.01). Moreover, LA had highly significant associations with brachial-ankle pulse wave velocity (P<0.001) and IMT (P<0.001). In conclusion, we demonstrated hemorheologically that monocyte-platelet conjugates play an important role in aortic stiffness and IMT in HD patients.     

Role of turmeric in oxidative modulation in end‐stage renal disease patients

Oxidative stress is considered as a major player in uremia‐associated morbidity and mortality in hemodialysis (HD) patients. The aim of this study was to evaluate the effects of turmeric on oxidative stress markers in HD patients. This study was a prospective and double‐blind randomized clinical trial. Fifty HD patients aged 18–60 years were recruited after fulfilling the inclusion criteria. Patients were randomly categorized into 2 groups: trial group received turmeric and control group received placebo for 8 weeks. Each patient in the trial group received turmeric, whereas the control group received starch for the same 8 weeks. Plasma malondialdehyde (MDA), red blood cell (RBC) antioxidant enzyme activities as glutathione peroxidase (GPX), glutathione reductase (GR), and catalase (CAT), cholesterol, high‐density lipoprotein‐cholesterol, low‐density lipoprotein‐cholesterol, triglyceride, albumin, and hemoglobin were also measured before and after study. Although MDA level was reduced in both groups, the ratio of decrease was significantly higher in the turmeric group (0.2 vs. 0.1, P = 0.040). Three enzymes of GPX, GR, and CAT levels were increased in both groups; the ratio of increased was significantly higher in the turmeric group for the CAT enzyme (0.73 vs. 0.54; P = 0.02). Also, significant elevation of albumin level in the turmeric group compared with the control group was observed (P = 0.001). Regular ingestion of turmeric reduces plasma MDA and increases RBC CAT activity and plasma albumin levels in HD patients. Turmeric showed no adverse effects.     

Dipyridamole stress echocardiography in diagnosis and prognosis of hemodialysis patients with asymptomatic coronary disease

The prevalence of coronary artery disease (CAD) is high in hemodialysis (HD) patients. The aim of the study was to assess the diagnostic and prognostic value of dipyridamole stress echocardiography (DSE) in nondiabetic HD patients without signs or symptoms of CAD. In 51 out of 158 evaluated HD patients (21 females, age 67 [33–85] years, HD duration 38 [9–271] months), resting echocardiography and DSE were performed. Exclusion criteria were known CAD, diabetes mellitus, and pulmonary and oncologic pathologies. Logistic regression analysis was carried out to identify predictors of abnormal DSE response, while Cox regression analysis was performed to determine variables associated with total and cardiovascular mortality, after 43.3 (11–60) months of follow‐up. Seven patients (14%) showed a positive response to DSE (DSE+). In 5/7, CAD was documented by angiography: All of them underwent coronary revascularization. DSE+ patients had significantly smaller body mass index than patients with a negative response (DSE‐): 21.7 ± 1.9 vs. 25.1 ± 3.4 kg/m² (p = 0.018). During follow‐up, 16 (31%) patients died. Older age hazard ratio [HR = 1.07; confidence interval (CI) = 1.01–1.12; p = 0.02] and higher plasma phosphate levels (HR = 10.41; CI = 2.30–47.17; p < 0.01) were predictors of total mortality. Male gender (HR = 22.7; CI = 1.45–354.4; p = 0.03), older age (HR = 1.24; CI = 1.03–1.50; p = 0.02), longer HD duration (HR = 1.13; CI = 1.01–1.26; p = 0.04), and positive response to DSE (HR = 5.82; CI = 1.04–32.65; p = 0.04) were associated with cardiovascular mortality. Ten percent of asymptomatic HD patients had significant CAD, but timely diagnosis did not seem to improve their prognosis. Total survival was associated with age and higher levels of plasma phosphate, while male gender, older age, longer HD duration, and DSE+ were predictors of cardiovascular mortality.     

The effects of hemodialysis treatment on the level of DNA strand breaks and oxidative DNA lesions measured by the comet assay

Hemodialysis patients have a higher risk for oxidative stress‐related complications, such as cardiovascular disease and cancer. The increased level of oxidative stress is due to several factors, e.g., the hemodialysis treatment itself and the uremic state. In the present study, the effects of dialysis treatment on the level of DNA breaks and oxidative DNA lesions in mononuclear cells were measured with the comet assay. Factors possibly affecting DNA damage (reported as % DNA in tail) such as the duration of dialysis, time since last dialysis session, years of dialysis treatment, nutritional status (measured as protein catabolic rate), age, and diabetes were also investigated. The levels of DNA breaks (13.6 ± 4.7 before dialysis) and oxidative DNA lesions (7.9 ± 4.8 before dialysis) were significantly higher in dialysis patients (n = 31) compared to the levels of DNA breaks (5.8 ± 1.1) and oxidative DNA lesions (3.4 ± 1.7) in 10 healthy controls (P < 0.001). A decrease of DNA breaks was observed after dialysis (P = 0.038), and the level of oxidative DNA lesions was higher when the time between two treatment sessions were 68 hours compared to 44 hours (P < 0.001). Older subjects had a higher level of DNA breaks (P = 0.003), a good nutritional status predicted a lower level of DNA breaks (P < 0.001), and the duration of the dialysis session was inversely correlated with oxidative DNA lesions (P = 0.014). Diabetes or years of dialysis treatment did not affect DNA damage. The observations in the present study suggest that accumulation of uremic toxins induce DNA damage. The hemodialysis treatment seems to change the DNA damage.