Ellen McMonagle

Oxidative Stress Is Increased in Critically Ill Patients with Acute Renal Failure

Patients with acute renal failure (ARF) experience a high mortality rate. Dysregulated inflammation and altered metabolism may increase oxidative stress in ARF patients. Thirty-eight patients who met the Program to Improve Care in Acute Renal Disease (PICARD) Study inclusion criteria underwent plasma protein oxidation and plasma cytokine measurements. For comparison, similar measurements were also performed in 21 critically ill patients without ARF, 28 patients with ESRD, and 49 healthy subjects. Plasma protein thiol oxidation was measured by spectrophotometry. Plasma protein carbonyl content and cytokine concentrations were measured by ELISA. Plasma protein thiol oxidation and carbonyl content were markedly different in ARF patients compared with healthy subjects, ESRD patients, and critically ill patients (P < 0.001 in all cases). There were significant but less marked differences in plasma protein oxidation between ESRD patients and critically ill patients compared with healthy subjects. Plasma protein thiol oxidation in ARF patients improved with dialysis (P < 0.001); however, there was significant plasma oxidant reaccumulation during the interdialytic period (P < 0.001) not due to rebound equilibration of compartmentalized solutes. Plasma proinflammatory cytokine levels were significantly higher (P < 0.05) in ARF patients and critically ill patients than in healthy subjects. Plasma protein oxidation is markedly increased in ARF patients compared with healthy subjects, ESRD patients, and critically ill patients. Increased oxidative stress may be an important target for nutritional and pharmacologic therapy in ARF patients.

Linkage of hypoalbuminemia, inflammation, and oxidative stress in patients receiving maintenance hemodialysis therapy

BACKGROUND Hypoalbuminemia is a powerful predictor of cardiovascular mortality in maintenance hemodialysis patients. Increased biomarkers of acute-phase inflammation and oxidative stress are highly prevalent and also correlate with cardiovascular morbidity and mortality. The extent to which hypoalbuminemia, biomarkers of inflammation, and biomarkers of oxidative stress are linked in this patient population is unknown. We hypothesized that a high proportion of hypoalbuminemic hemodialysis patients also would manifest increased levels of biomarkers of inflammation and oxidative stress. METHODS We surveyed 600 maintenance hemodialysis patients and identified 18 severely hypoalbuminemic patients (serum albumin level < 3.2 g/dL [32 g/L]) without recent infection or hospitalization. We then identified 18 age-, race-, sex-, and diabetes-matched normoalbuminemic hemodialysis patients, as well as 18 age-, race-, sex-, and diabetes-matched healthy subjects, for cohort comparison. Measurements of plasma interleukin-6 (IL-6) levels, plasma protein reduced thiol content, plasma protein carbonyl content, and plasma free F2-isoprostane levels, as well as serum concentrations of C-reactive protein (CRP) and prealbumin, were performed for study purposes. RESULTS Levels of serum CRP, IL-6, plasma protein thiol oxidation, and protein carbonyl formation were significantly elevated in both hypoalbuminemic and normoalbuminemic hemodialysis patients compared with healthy subjects and also were significantly different in hypoalbuminemic maintenance dialysis patients compared with normoalbuminemic hemodialysis patients. Prealbumin levels were significantly lower in hypoalbuminemic hemodialysis patients than in other groups. CONCLUSION There is a high prevalence of inflammation and oxidative stress in the maintenance hemodialysis population. Levels of inflammatory and oxidative stress biomarkers are increased further in hypoalbuminemic compared with normoalbuminemic dialysis patients. Hypoalbuminemia, acute-phase inflammation, and oxidative stress may act synergistically to increase cardiovascular morbidity and mortality risk in maintenance hemodialysis patients.

Hemodialysis Acutely Improves Hepatic CYP3A4 Metabolic Activity

The uremic syndrome remains poorly understood despite the widespread availability of dialysis for almost four decades. To date, assessment of the biologic activity of uremic toxins has focused primarily on in vitro effects, rather than on specific biochemical pathways or enzymatic activity in vivo. The activity of cytochrome P450 (CYP) 3A4, the most important enzyme in human drug metabolism, is decreased in uremia. The purpose of this study was to assess the effect of hemodialysis and hence varying concentrations of uremic toxins on CYP3A4 activity using the 14C-erythromycin breath test and the traditional phenotypic trait measure, 20-min 14CO2 flux. CYP3A4 activity increased by 27% postdialysis (P = 0.002 compared with predialysis) and was significantly inversely related to plasma blood urea nitrogen concentration (rs= -0.50, P = 0.012), but not to several middle molecules. This is the first study in humans characterizing uremia as a state in which hepatic CYP3A4 activity is acutely improved by hemodialysis.

Manifestations of Oxidant Stress in Uremia

Oxidant injury is now thought to contribute to the pathogenesis of a wide array of disease states [1, 2]. These include the development of atherosclerosis, tissue injury related to ischemia-reperfusion injury, and cellular changes associated with both the aging process and carcinogenesis. In certain inflammatory disease states, such as the development of acute respiratory disease syndrome (ARDS), acute renal failure and inflammatory bowel disease, tissue injury can be mediated by oxidative reactions. Oxidative stress can result from the variety of biochemical pathways ranging from metal-catalyzed oxidative reactions to the release of reactive oxygen compounds such as superoxide anion, hydrogen peroxide and hypochlorous acid from activated phagocytic cells [3, 4]. Recently, the importance of myeloperoxidase-catalyzed oxidative reactions (with hypochlorous acid as the major oxidant in causing tissue injury by phagocytic cells) have been emphasized [5]. Thus in vivo detection of injury patterns induced by HOCl would be useful in characterizing inflammatory oxidative injury. In many human disease states, the understanding of how oxidative reactions contribute to the disease process is limited because of inaccessibility of important tissue samples during the disease process. For example, in atherosclerosis, oxidative modification of lipoproteins likely takes place in the subendothelium which in humans is not routinely accessible for laboratory measurements [6]. In other disease processes that affect patients such as acute renal failure or ARDS, sampling of biological fluids and relevant tissue may not be attainable until well after the injury phase has occurred. Because of their ready access to repeated sampling, biomolecules that develop as a result of oxidative stress in the plasma are attractive in understanding how human disease may result from specific pathways of oxidative stress. Plasma proteins constitute an important target for analysis of oxidative modification, both because of their relative stability in plasma and because of the variety of oxidative reactions that can take place [7].

Effects of Combination Tocopherols and Alpha Lipoic Acid Therapy on Oxidative Stress and Inflammatory Biomarkers in Chronic Kidney Disease

OBJECTIVE Although increased oxidative stress and inflammation are highly prevalent in chronic kidney disease (CKD), few studies have investigated whether oral antioxidant therapy can alter markers of inflammation or oxidative stress in patients with CKD. The purpose of this study was to investigate whether a combination of mixed tocopherols and alpha lipoic acid (ALA) would alter biomarkers of oxidative stress and inflammation in subjects with stage 3 to 4 CKD. METHODS This was a prospective, randomized, double-blind, placebo-controlled pilot trial. In all, 62 subjects were enrolled and were randomly assigned to receive a combination of mixed tocopherols 666 IU/day, in addition to ALA 600 mg/day, or their matching placebos for a total of 8 weeks. Plasma F(2)-isoprostane and protein thiol concentration were measured as biomarkers of oxidative stress, and C-reactive protein and interleukin-6 concentration as biomarkers of systemic inflammation. RESULTS There were no significant differences in demographics, diabetic status, or estimated glomerular filtration rate between study treatment and placebo groups at baseline. Of the 62 randomized subjects, 58 (93%) completed the study protocol. After 2 months of treatment, there were no significant changes in the concentrations of F(2)-isoprostanes, protein thiols, C-reactive protein, and interleukin-6 with respect to treatment with mixed tocopherols and ALA as compared with matching placebos, whether analyzed as intention to treat or as treated. Diabetic status and baseline body mass index did not influence the results. CONCLUSIONS Combination of oral mixed tocopherols and ALA treatment for 2 months does not influence biomarkers of oxidative stress and inflammation in patients with stage 3 to 4 CKD.

Kt/V, Nutritional Parameters, Serum Cortisol, and Insulin Growth Factor-1 Levels and Patient Outcome in Hemodialysis

Despite many technical advances in dialysis care, morbidity and mortality in chronic hemodialysis patients in the United States remains high. In this study, we analyzed the effects of Kt/V, nutritional parameters (serum albumin level, triceps skin-fold thickness, mid-arm muscle circumference, and normalized protein catabolic rate), and predialysis serum cortisol and insulin growth factor-1 levels on predicting morbidity and mortality. The cohort studied consisted of 52 patients recruited from a single outpatient dialysis facility. Cox proportional hazards modeling indicated that only Kt/V predicted subsequent mortality (P = 0.02), while both predialysis cortisol levels (P = 0.03) and Kt/V (P = 0.03) predicted hospitalization. Kaplan-Meier analysis demonstrated that the ability of cortisol levels to predict hospitalization was largely confined to the group with values greater than 22 micrograms/dL predialysis. High serum cortisol levels were correlated with low serum albumin levels and a trend toward low triceps skin-fold thickness and higher normalized protein catabolic rate, suggesting a catabolic state. Both predialysis serum cortisol and insulin growth factor-1 levels were higher than those in age- and sex-matched normal human controls. These results demonstrate the importance role of Kt/V in predicting subsequent hospitalization rates and mortality, and that high predialysis serum cortisol levels correlate with a high hospitalization rate.

Effects of aprotinin on complement and granulocyte activation during ex vivo hemodialysis

Hemodialysis with cellulosic membranes results in complement activation, granulocytopenia, and granulocyte activation. To further investigate the relationship between complement activation and granulocyte activation, we developed a model of ex vivo hemodialysis with blood flow, dialysate flow, and dialysate composition similar to in vivo hemodialysis. We used this model to investigate the effects of aprotinin, a potent serine protease inhibitor frequently used as an anti-inflammatory agent during cardiopulmonary bypass surgery, on both complement and granulocyte activation. Seven normal human volunteers were phlebotomized for ex vivo hemodialysis on two occasions each, one with and once without 800,000 kallikrein inhibitor units of aprotinin added to the circuit. Measurements were made of complement activation (radioimmunoassay for C3a desArg and C5a desArg), as well as granulocyte activation (flow cytometric measurements of reactive oxygen species (ROS) production, granulocyte CD11b-CD18 [MAC-1, CR3] expression, and CD62-L [L-selectin] expression). Statistically significant elevations in C3a desArg levels occurred by 10 minutes and reached a maximum of 5,367 +/- 712 ng/mL by 60 minutes after the initiation of ex vivo hemodialysis. Plasma C5a levels were elevated to 236 +/- 32 ng/mL at 60 minutes compared with 45 +/- 15 ng/mL predialysis. Aprotinin was able to significantly inhibit dialysis-induced C3a generation (peak 2,456 +/- 572 ng/mL at 60 minutes) as well as C5a generation (86 +/- 23 ng/mL at 60 minutes). During ex vivo hemodialysis, there was also a significant increase in granulocyte ROS production, MAC-1 upregulation, and L-selectin downregulation. Changes in granulocyte activation were not affected by the administration of aprotinin.(ABSTRACT TRUNCATED AT 250 WORDS)

Baseline Oxysterols and Other Markers of Oxidative Stress, Inflammation and Malnutrition in the Vitamin E and Intima Media Thickness Progression in End-Stage Renal Disease (VIPER) Cohort

Background and Objectives: Oxysterols are markers of oxidative stress, levels of which have not yet been reported in hemodialysis (HD) patients. This study was designed to compare levels of the oxysterols 7-ketocholesterol (7KC) and 7β-hydroxycholesterol (7βOH) between a cohort of HD patients and healthy controls. Methods: This nested cross-sectional study reflects baseline (pre-intervention) values for markers of oxidative stress, inflammation and nutrition status in the 160-member vitamin E and carotid intima media thickness progression in end-stage renal disease (VIPER) cohort (age 64.1 ± 8.8, 33.5% female). Age- and sex-matched healthy volunteers served as controls. Plasma oxysterols 7KC and 7βOH were determined by isotope dilution gas chromatography/mass spectrometry. Results: Despite higher plasma α-tocopherol levels in HD patients than controls (36.0 ± 9.3 vs. 31.8 ± 8.4 µmol/l, p = 0.007), 7KC levels (9.8 ± 6.9 vs. 5.9 ± 2.8 nmol/mmol cholesterol, p < 0.0001) and 7βOH levels (8.7 ± 4.3 vs. 2.7 ± 1.6 nmol/mmol cholesterol, p < 0.0001) were higher in HD patients. The oxysterol 7βOH was significantly, inversely associated with prealbumin (r = –0.18, p = 0.03), though neither oxysterol was significantly associated with any other marker of oxidative stress, inflammation or nutrition status and did not discriminate for CVD in HD patients. Conclusions: Elevated levels of the oxysterols 7KC and 7βOH indicate that HD patients are in a state of oxidative stress compared to healthy controls. However, oxysterols 7KC and 7βOH did not appear to contribute additional information about oxidative stress among HD patients.