Further evidence that oxidative stress may be a risk factor responsible for the development of atherosclerosis

Leukocyte 8-hydroxy-2'-deoxyguanosine as an oxidative stress marker to predict cardiovascular events and death in chronic hemodialysis patients

BACKGROUND

Hemodialysis patients have a markedly increased risk of cardiovascular (CV) morbidity and mortality. Oxidative stress plays a pathogenic role in the progression of atherosclerosis and CV disease among chronic hemodialysis patients. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) content in leukocyte deoxyribonucleic acid (DNA) has been shown as a sensitive and well-known biomarker of oxidant-induced DNA damage in chronic hemodialysis patients.

METHODS

We conducted a retrospective cohort study to investigate the association of leukocyte 8-OHdG and CV events and deaths in patients of chronic hemodialysis. In this study, 217 chronic hemodialysis patients were recruited from 2016 to 2021. The 8-OHdG content of leukocyte DNA was measured by a high-performance liquid chromatography electrochemical detection method. Study outcomes were CV events as well as CV and all-cause deaths. The patients were followed until May 2021.

RESULTS

The median follow-up period was 34.8 months. At the end of May 2021, 57 first CV events and 89 all-CV events occurred. Among the first and all CV events, 17 (29.8%) and 32 (36.0%) were fatal, respectively. Multivariate Cox regression analysis showed per 1/10 5 dG increment in leukocyte 8-OHdG values increased risk of CV events (adjusted hazard ratio [aHR], 1.19; 95% CI, 1.10-1.41; p < 0.001), CV death (aHR, 1.27; 95% CI, 1.03-1.72; p = 0.034), and all-cause death (aHR, 1.11; 95% CI, 1.01-1.30; p = 0.038).

CONCLUSION

This is the first study to demonstrate that oxidative stress assessed by 8-OHdG levels of leukocyte DNA predicted CV events as well as CV and all-cause deaths among chronic hemodialysis patients.

Polycyclic aromatic hydrocarbon exposure and atherosclerotic cardiovascular disease risk in urban adults: The mediating role of oxidatively damaged DNA

Polycyclic aromatic hydrocarbon (PAH) exposure has been considered a risk factor for cardiovascular diseases (CVD), whereas possible mechanisms for this association have not been fully understood. This study focused on exploring the potential effect of oxidatively damaged DNA on the relationships between PAH exposure and the 10-year atherosclerotic CVD (ASCVD) risk. Urinary levels of monohydroxy PAH metabolites (OH-PAHs) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG, the typical biomarker for oxidatively damaged DNA) were measured among 3052 subjects in the baseline of the Wuhan-Zhuhai cohort. The relationships between urinary OH-PAHs, 8-oxodG and 10-year risk of ASCVD were analyzed by linear mixed models and logistic regression models, respectively. The mediation analysis was further applied to explore the role of 8-oxodG in the relationship between urinary OH-PAHs and 10-year ASCVD risk. After controlling for potential confounders, the log-transformed level of total urinary low molecular weight OH-PAHs (∑LMW OH-PAHs) was significantly associated with an elevated risk of 10-year ASCVD [odds ratio (OR) = 1.222, 95% confidence interval (CI): 1.065-1.402]. More specifically, significantly positive dose-response relationships between total urinary hydroxynaphthalene (∑OHNa), hydroxyfluorene (∑OHFlu), hydroxyphenanthrene (∑OHPh) and 10-year ASCVD risk were observed (all P for trend <0.05). We also found positive relationships between urinary OH-PAH levels and 8-oxodG, as well as between urinary 8-oxodG levels and 10-year risk of ASCVD. Moreover, mediation analyses indicated that urinary 8-oxodG mediated 14.49%, 12.62% and 10.55% of the associations between urinary ∑LMW OH-PAHs, ∑OHNa, ∑OHFlu and 10-year ASCVD risk, respectively. These findings suggest that the oxidatively damaged DNA pathway may be a possible mechanism underlying PAH-associated ASCVD risk elevation.

Approaches and Methods to Measure Oxidative Stress in Clinical Samples: Research Applications in the Cancer Field

Reactive oxygen species (ROS) are common by-products of normal aerobic cellular metabolism and play important physiological roles in intracellular cell signaling and homeostasis. The human body is equipped with antioxidant systems to regulate the levels of these free radicals and maintain proper physiological function. However, a condition known as oxidative stress (OS) occurs, when ROS overwhelm the body's ability to readily detoxify them. Excessive amounts of free radicals generated under OS conditions cause oxidative damage to proteins, lipids, and nucleic acids, severely compromising cell health and contributing to disease development, including cancer. Biomarkers of OS can therefore be exploited as important tools in the assessment of disease status in humans. In the present review, we discuss different approaches used for the evaluation of OS in clinical samples. The described methods are limited in their ability to reflect on OS only partially, revealing the need of more integrative approaches examining both pro- and antioxidant reactions with higher sensitivity to physiological/pathological alternations. We also provide an overview of recent findings of OS in patients with different types of cancer. Identification of OS biomarkers in clinical samples of cancer patients and defining their roles in carcinogenesis hold great promise in promoting the development of targeted therapeutic approaches and diagnostic strategies assessing disease status. However, considerable data variability across laboratories makes it difficult to draw general conclusions on the significance of these OS biomarkers. To our knowledge, no adequate comparison has yet been performed between different biomarkers and the methodologies used to measure them, making it difficult to conduct a meta-analysis of findings from different groups. A critical evaluation and adaptation of proposed methodologies available in the literature should therefore be undertaken, to enable the investigators to choose the most suitable procedure for each chosen biomarker.

Assessing Free-Radical-Mediated DNA Damage during Cardiac Surgery: 8-Oxo-7,8-dihydro-2'-deoxyguanosine as a Putative Biomarker

Coronary artery bypass grafting (CABG), one of the most common cardiac surgical procedures, is characterized by a burst of oxidative stress. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), produced following DNA repairing, is used as an indicator of oxidative DNA damage in humans. The effect of CABG on oxidative-induced DNA damage, evaluated through the measurement of urinary 8-oxodG by a developed and validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method in 52 coronary artery disease (CAD) patients, was assessed before (T0), five days (T1), and six months (T2) after CABG procedure. These results were compared with those obtained in 40 subjects with cardiovascular risk factors and without overt cardiovascular disease (CTR). Baseline (T0) 8-oxodG was higher in CAD than in CTR (p = 0.035). A significant burst was detected at T1 (p = 0.019), while at T2, 8-oxodG levels were significantly lower than those measured at T0 (p < 0.0001) and comparable to those found in CTR (p = 0.73). A similar trend was observed for urinary 8-iso-prostaglandin F_2α (8-isoPGF_2α), a reliable marker of oxidative stress. In the whole population baseline, 8-oxodG significantly correlated with 8-isoPGF_2α levels (r = 0.323, p = 0.002). These data argue for CABG procedure in CAD patients as inducing a short-term increase in oxidative DNA damage, as revealed by 8-oxodG concentrations, and a long-term return of such metabolite toward physiological levels.

Pandora's Box: mitochondrial defects in ischaemic heart disease and stroke

Ischaemic heart disease and stroke are vascular events with serious health consequences worldwide. Recent genetic and epigenetic techniques have revealed many genetic determinants of these vascular events and simplified the approaches to research focused on ischaemic heart disease and stroke. The pathogenetic mechanisms of ischaemic heart disease and stroke are complex, with mitochondrial involvement (partially or entirely) recently gaining substantial support. Not only can mitochondrial reactive oxygen species give rise to ischaemic heart disease and stroke by production of oxidised low-density lipoprotein and induction of apoptosis, but the impact on pericytes contributes directly to the pathogenesis. Over the past two decades, publications implicate the causative role of nuclear genes in the development of ischaemic heart disease and stroke, in contrast to the potential role of mitochondrial DNA (mtDNA) in the pathophysiology of the disorders, which is much less understood, although recent studies do demonstrate that the involvement of mitochondria and mtDNA in the development of ischaemic heart disease and stroke is likely to be larger than originally thought, with the novel discovery of links among mitochondria, mtDNA and vascular events. Here we explore the molecular events and mtDNA alterations in relation to the role of mitochondria in ischaemic heart disease and stroke.

Citrate and albumin facilitate transferrin iron loading in the presence of phosphate

Labile plasma iron (LPI) is redox active, exchangeable iron that catalyzes the formation of reactive oxygen species. Serum transferrin binds iron in a non-exchangeable form and delivers iron to cells. In several inflammatory diseases serum LPI increases but the reason LPI forms is unknown. This work evaluates possible pathways leading to LPI and examines potential mediators of apo transferrin iron loading to prevent LPI. Previously phosphate was shown to inhibit iron loading into apo transferrin by competitively binding free Fe³⁺. The reaction of Fe³⁺ with phosphate produced a soluble ferric phosphate complex. In this study we evaluate iron loading into transferrin under physiologically relevant phosphate conditions to evaluate the roles of citrate and albumin in mediating iron delivery into apo transferrin. We report that preformed Fe³⁺-citrate was loaded into apo transferrin and was not inhibited by phosphate. A competition study evaluated reactions when Fe³⁺ was added to a solution with citrate, phosphate and apo transferrin. The results showed citrate marginally improved the delivery of Fe³⁺ to apo transferrin. Studies adding Fe³⁺ to a solution with phosphate, albumin and apo transferrin showed that albumin improved Fe³⁺ loading into apo transferrin. The most efficient Fe³⁺ loading into apo transferrin in a phosphate solution occurred when both citrate and albumin were present at physiological concentrations. Citrate and albumin overcame phosphate inhibition and loaded apo transferrin equal to the control of Fe³⁺ added to apo transferrin. Our results suggest a physiologically important role for albumin and citrate for apo transferrin iron loading.

Iron and peripheral arterial disease: revisiting the iron hypothesis in a different light

The relationship between iron status and atherosclerosis has long been a topic of debate in the literature. Despite more than 25 years of research, there is no consensus regarding a causal relationship. To date, the vast majority of studies have focused on iron burden with respect to a hypothesized role in the onset and progression of coronary artery disease. However, the effect of iron in the coronary arterial system may differ mechanistically and therefore clinically from its effect in the peripheral arterial system. This review will summarize the biochemical, pathologic, animal, and clinical research data with respect to iron and atherosclerosis. This background will be expanded upon to provide insights into ongoing studies and paths for future investigations into the role of iron and peripheral arterial disease.

Antioxidant enzymes status and reproductive health of adult male workers exposed to brick kiln pollutants in Pakistan

The present study was designed to study the effect of brick kilns emissions on the reproductive health and biochemical status of brick kiln workers and people living in the area near brick kilns. Body mass index (BMI) was significantly reduced in brick makers, carriers, and bakers compared to the control. Red blood cells count and hematocrit (%) were significantly high in brick bakers while MCH was significantly reduced in brick makers and brick bakers. Heavy metals (lead, cadmium, and chromium) concentration in whole blood of the brick kiln workers were significantly higher as compared to the control. Antioxidant enzymes (CAT, SOD, POD, GSH, and GR) were significantly reduced in brick kiln workers as compared to the control while TBARS level were significantly high in brick bakers as compared to the control. Plasma leutinizing hormone (LH) was significantly high in brick bakers while testosterone concentrations were significantly reduced in brick makers, carriers, and bakers. The present study shows that brick kiln workers and people living in the brick kiln vicinity are exposed to heavy metals and other pollutants that is a serious threat to their health. Alternate technology is needed to be developed and brick kilns should be replaced.

8-Hydroxy-2-Deoxyguanosine Levels and Cardiovascular Disease: A Systematic Review and Meta-Analysis of the Literature

SIGNIFICANCE

8-Hydroxy-2-deoxyguanosine (8-OHdG) is generated after the repair of ROS-mediated DNA damages and, thus, is one of the most widely recognized biomarkers of oxidative damage of DNA because guanosine is the most oxidized among the DNA nucleobases. In several pathological conditions, high urinary levels of oxidized DNA-derived metabolites have been reported (e.g., cancer, atherosclerosis, hypertension, and diabetes).

RECENT ADVANCES

Even if published studies have shown that DNA damage is significantly associated with the development of atherosclerosis, the exact role of this damage in the onset and progression of this pathology is not fully understood, and the association of oxidative damage to DNA with cardiovascular disease (CVD) still needs to be more extensively investigated. We performed a meta-analysis of the literature to investigate the association among 8-OHdG levels and CVD.

CRITICAL ISSUES

Fourteen studies (810 CVD patients and 1106 controls) were included in the analysis. We found that CVD patients showed higher 8-OHdG levels than controls (SMD: 1.04, 95%CI: 0.61, 1.47, p < 0.001, I(2) = 94%, p < 0.001). The difference was confirmed both in studies in which 8-OHdG levels were assessed in urine (MD: 4.43, 95%CI: 1.71, 7.15, p = 0.001) and in blood samples (MD: 1.42, 95%CI: 0.64, 2.21, p = 0.0004). Meta-regression models showed that age, hypertension, and male gender significantly impacted on the difference in 8-OHdG levels among CVD patients and controls.

FUTURE DIRECTIONS

8-OHdG levels are higher in patients with CVD than in controls. However, larger prospective studies are needed to test 8-OHdG as a predictor of CVD.

Age and metabolic risk factors associated with oxidatively damaged DNA in human peripheral blood mononuclear cells

Aging is associated with oxidative stress-generated damage to DNA and this could be related to metabolic disturbances. This study investigated the association between levels of oxidatively damaged DNA in peripheral blood mononuclear cells (PBMCs) and metabolic risk factors in 1,019 subjects, aged 18-93 years. DNA damage was analyzed as strand breaks by the comet assay and levels of formamidopyrimidine (FPG-) and human 8-oxoguanine DNA glycosylase 1 (hOGG1)-sensitive sites There was an association between age and levels of FPG-sensitive sites for women, but not for men. The same tendency was observed for the level of hOGG1-sensitive sites, whereas there was no association with the level of strand breaks. The effect of age on oxidatively damaged DNA in women disappeared in multivariate models, which showed robust positive associations between DNA damage and plasma levels of triglycerides, cholesterol and glycosylated hemoglobin (HbA_1c). In the group of men, there were significant positive associations between alcohol intake, HbA_1c and FPG-sensitive sites in multivariate analysis. The levels of metabolic risk factors were positively associated with age, yet only few subjects fulfilled all metabolic syndrome criteria. In summary, positive associations between age and levels of oxidatively damaged DNA appeared mediated by age-related increases in metabolic risk factors.

DNA damage in non-communicable diseases: A clinical and epidemiological perspective

Non-communicable diseases (NCDs) are a leading cause of death and disability, representing 63% of the total death number worldwide. A characteristic phenotype of these diseases is the accelerated aging, which is the result of phenomena such as accumulated DNA damage, telomere capping loss and subcellular irreversible/nonrepaired oxidative damage. DNA damage, mostly oxidative, plays a key role in the development of most common NCDs. The present review will gather some of the most relevant knowledge concerning the presence of DNA damage in NCDs focusing on cardiovascular diseases, diabetes, chronic obstructive pulmonary disease, and neurodegenerative disorders, and discussing a selection of papers from the most informative literature. The challenge of comorbidity and the potential offered by new systems approaches for introducing these biomarkers into the clinical decision process will be discussed. Systems Medicine platforms represent the most suitable approach to personalized medicine, enabling to identify new patterns in the pathogenesis, diagnosis and prognosis of chronic diseases.

Does morphology of carotid plaque depend on patient's oxidative stress?

OBJECTIVES

This study explored the relationship between oxidative stress biomarkers and stability of carotid plaque. We decided to analyze the broad range of parameters describing oxidative stress in patients with carotid stenosis.

DESIGN AND METHODS

124 consecutive patients undergoing carotid endarterectomy were enrolled in the study group. The control group consisted of 49 patients without symptoms of atherosclerosis. The stability of carotid plaques was assessed using GSM (gray-scale median) scoring system and the study group was divided into three subgroups according to echogenicity of the plaque. The following parameters of oxidative stress/DNA damage were analyzed: i) urinary excretion of the products of oxidative DNA damage repair; ii) the background level of 8-oxo-7,8-dihydro-2'-deoxyguanosine in leukocytes' DNA and in atherosclerotic plaques; and iii) the concentrations of antioxidant vitamins, uric acid and C-reactive protein in plasma.

RESULTS

Oxidative stress (described by redox status) was higher in the patient group than in the control group. There is a correlation between oxidative stress of the patients and stability of the plaque, echolucent plaques (GSM<25) being associated with the highest antioxidant level and lowest excretion of DNA repair markers.

CONCLUSIONS

The plaque formation/morphology may depend on local environment and is independent of oxidative stress/inflammation observed on the level of the whole body.

Association of oxidative DNA damage and C-reactive protein in women at risk for cardiovascular disease

OBJECTIVE

The aim of the current study was to examine the relationship between clinical markers of inflammation and 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG), an oxidative stress marker, in middle-aged women drawn from the HANDLS study, a longitudinal epidemiological study.

METHODS AND RESULTS

We examined commonly assayed markers of inflammation, the DNA base adduct 8-oxodG, a marker of oxidative stress, and cardiovascular risk factors in a cohort of women matched on age and race in 3 groups (n=39 per group) who had low (<3 mg/L) high-sensitivity C-reactive protein (hsCRP), mid (>3-20 mg/L), and high (>20 mg/L) hsCRP. We found a significant relationship between hsCRP level and the oxidative stress marker, 8-oxodG. 8-oxodG was positively correlated with systolic blood pressure, pulse pressure, and interleukin-23. hsCRP was associated with obesity variables, high-density lipoprotein, serum insulin levels, interleukin-12p70 and intracellular adhesion molecule-1. Incubation of primary human endothelial cells with hsCRP generated reactive oxygen species in vitro. Furthermore, hsCRP specifically induced DNA base lesions, but not other forms of DNA damage, including single and double strand breaks.

CONCLUSIONS

These data suggest that in women 8-oxodG is associated with hsCRP and is independently related to select cardiovascular risk factors. Our data in women suggest that hsCRP may contribute to cardiovascular disease by increasing oxidative stress.

Non transferrin bound iron: nature, manifestations and analytical approaches for estimation

Iron is an essential trace element and plays a number of vital roles in biological system. It also leads the chains of pathological actions if present in excess and/or present in free form. Major portion of iron in circulation is associated with transferrin, a classical iron transporter, which prevent the existence of free iron. The fraction of iron which is free of transferrin is known as "non transferrin bound iron". Along with the incidence in iron over loaded patient non transferrin bound iron has been indicated in patients without iron overload. It has been suggested as cause as well as consequence in a number of pathological conditions. The major organs influenced by iron toxicity are heart, pancreas, kidney, organs involved in hematopoiesis etc. The most commonly suggested way for iron mediated pathogenesis is through increased oxidative stress and their secondary effects. Generation of free oxygen radicals by iron has been well documented in Fenton chemistry and Haber-Weiss reaction. Non transferrin bound iron has obvious chance to generate the free reactive radicals as it is not been shielded by the protective carrier protein apo transferrin. The nature of non transferrin bound iron is not clear at present time but it is definitely a group of heterogenous iron forms free from transferrin and ferritin. A variety of analytical approaches like colorimetry, chromatography, fluorimetry etc. have been experimented in different research laboratories for estimation of non transferrin bound iron. However the universally accepted gold standard method which can be operated in pathological laboratories is still to be developed.

Multiple aberrations in shared inflammatory and oxidative & nitrosative stress (IO&NS) pathways explain the co-association of depression and cardiovascular disorder (CVD), and the increased risk for CVD and due mortality in depressed patients

There is evidence that there is a bidirectional relationship between major depression and cardiovascular disorder (CVD): depressed patients are a population at risk for increased cardiac morbidity and mortality, and depression is more frequent in patients who suffer from CVD. There is also evidence that inflammatory and oxidative and nitrosative stress (IO&NS) pathways underpin the common pathophysiology of both CVD and major depression. Activation of these pathways may increase risk for both disorders and contribute to shared risk. The shared IO&NS pathways that may contribute to CVD and depression comprise the following: increased levels of pro-inflammatory cytokines, like interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-12, tumor necrosis factor-α, and interferon-γ; T cell activation; increased acute phase proteins, like C-reactive protein, haptoglobin, fibrinogen and α1-antitrypsin; complement factors; increased LPS load through bacterial translocation and subsequent gut-derived inflammation; induction of indoleamine 2,3-dioxygenase with increased levels of tryptophan catabolites; decreased levels of antioxidants, like coenzyme Q10, zinc, vitamin E, glutathione and glutathione peroxidase; increased O&NS characterized by oxidative damage to low density lipoprotein (LDL) and phospholipid inositol, increased malondialdehyde, and damage to DNA and mitochondria; increased nitrosative stress; and decreased ω3 polyunsaturated fatty acids (PUFAs). The complex interplay between the abovementioned IO&NS pathways in depression results in pro-atherogenic effects and should be regarded as a risk factor to future clinical CVD and due mortality. We suggest that major depression should be added as a risk factor to the Charlson "comorbidity" index. It is advised that patients with (sub)chronic or recurrent major depression should routinely be assessed by serology tests to predict if they have an increased risk to cardiovascular disorders.

Parenteral iron formulations differentially affect MCP-1, HO-1, and NGAL gene expression and renal responses to injury

Despite their prooxidant effects, ferric iron compounds are routinely administered to patients with renal disease to correct Fe deficiency. This study assessed relative degrees to which three clinically employed Fe formulations [Fe sucrose (FeS); Fe gluconate (FeG); ferumoxytol (FMX)] impact renal redox- sensitive signaling, cytotoxicity, and responses to superimposed stress [endotoxin; glycerol-induced acute renal failure (ARF)]. Cultured human proximal tubule (HK-2) cells, isolated proximal tubule segments (PTS), or mice were exposed to variable, but equal, amounts of FeS, FeG, or FMX. Oxidant-stimulated signaling was assessed by heme oxygenase-1 (HO-1) or monocyte chemoattractant protein (MCP)-1 mRNA induction. Cell injury was gauged by MTT assay (HK-2 cells), %LDH release (PTS), or renal cortical neutrophil gelatinase-associated lipoprotein (NGAL) protein/mRNA levels. Endotoxin sensitivity and ARF severity were assessed by TNF-alpha and blood urea nitrogen concentrations, respectively. FeS and FeG induced lethal cell injury (in HK-2 cells, PTS), increased HO-1 and MCP-1 mRNAs (HK-2 cells; in vivo), and markedly raised plasma ( approximately 10 times), and renal cortical ( approximately 3 times) NGAL protein levels. Both renal and extrarenal (e.g., hepatic) NGAL production likely contributed to these results, based on assessments of tissue and HK-2 cell NGAL mRNA. FeS pretreatment exacerbated endotoxemia. However, it conferred marked protection against the glycerol model of ARF (halving azotemia). FMX appeared to be "bioneutral," as it exerted none of the above noted FeS/FeG effects. We conclude that 1) parenteral iron formulations that stimulate redox signaling can evoke cyto/nephrotoxicity; 2) secondary adaptive responses to this injury (e.g., HO-1/NGAL induction) can initiate a renal tubular cytoresistant state; this suggests a potential new clinical application for intravenous Fe therapy; and 3) FMX is bioneutral regarding these responses. The clinical implication(s) of the latter, vis a vis the treatment of Fe deficiency in renal disease patients, remains to be defined.

Urinary excretion rates of 8-oxoGua and 8-oxodG and antioxidant vitamins level as a measure of oxidative status in healthy, full-term newborns

The aim of the present study was to evaluate the oxidative status in healthy full-term children and piglets. Urinary excretion of 8-oxoGua (8-oxoguanine) and 8-oxodG (8-oxo-2'-deoxyguanosine) were determined using HPLC/GS/MS methodology and concentrations of vitamins A, C and E with HPLC technique. The levels of 8-oxoGua in urine samples were about 7-8 times higher in newborn children and piglets when compared with the level of adult subjects, while in the case of 8-oxodG the difference was about 2.5 times. The levels of vitamin C and E in umbilical cord blood of newborn children significantly depend on the concentration of these compounds in their mother's blood. However, the values of vitamin C in human's cord blood were about 2-times higher than in respective mother blood, while the level of vitamin E showed an opposite trend. The results suggest that: (i) healthy, full-term newborns are under potential oxidative stress; (ii) urinary excretion of 8-oxoGua and 8-oxodG may be a good marker of oxidative stress in newborns; and (iii) antioxidant vitamins, especially vitamin C, play an important role in protecting newborns against oxidative stress.

Urinary levels of oxidative DNA and RNA damage among workers exposed to polycyclic aromatic hydrocarbons in silicon production: comparison with 1-hydroxypyrene

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous occupational and environmental pollutants and the urinary excretion of 1-hydroxypyrene (1-OHP) is classically measured for the determination of PAH exposure internal dose. Some of PAH are tumorigenic due to their metabolites ability to generate DNA adducts and oxidative DNA damage through the production of reactive oxygen species during metabolism. 8-hydroxy-7,8-dihydro-2'-deoxyguanosine (8-OHdGuo) is one of the major oxidative DNA lesions and its use as a potential biomarker of genotoxic PAH occupational exposure should be evaluated. Indeed conflicting results are frequently reported in occupational studies in terms of correlation between 8-OHdGuo urinary levels and PAH exposure. The aim of our study was therefore to determine the potential for PAH occupational exposure to increase urinary oxidative DNA damage. The population consisted of 68 male workers employed in silicon production. The urinary concentrations of 8-OHdGuo and its homologue in RNA, 8-hydroxy-7,8-dihydroguanosine (8-OHGuo) were determined using high performance liquid chromatography (HPLC) coupled to tandem mass spectrometry, whereas those of 1-OHP were measured using HPLC with fluorescence detection. Individual variation rates were calculated on a working day and a working week. The results indicated that, while 1-OHP levels strongly increased on a working day and even more on a working week, 8-OHdGuo and 8-OHGuo urinary levels did not show similar significant increases. Moreover, no correlation between 1-OHP and oxidative DNA and RNA lesions was found. Consequently, urinary 8-OHdGuo and 8-OHGuo did not seem to be relevant biomarkers of genotoxic PAH exposure in the case of the silicon plant studied.

Prolonged exposure to LPS increases iron, heme, and p22phox levels and NADPH oxidase activity in human aortic endothelial cells: inhibition by desferrioxamine

OBJECTIVE

Vascular oxidative stress and inflammation are contributing factors in atherosclerosis. We recently found that the iron chelator, desferrioxamine (DFO), suppresses NADPH oxidase-mediated oxidative stress and expression of cellular adhesion molecules in mice treated with lipopolysaccharide (LPS). The objective of the present study was to investigate whether and how LPS and iron enhance, and DFO inhibits, NADPH oxidase activity in human aortic endothelial cells (HAECs).

METHODS AND RESULTS

Incubation of HAECs for 24 hours with 5 microg/mL LPS led to a 4-fold increase in NADPH oxidase activity, which was strongly suppressed by pretreatment of the cells for 24 hours with 100 micromol/L DFO. Incubating HAECs with LPS also significantly increased cellular iron and heme levels and mRNA and protein levels of p22phox, a heme-containing, catalytic subunit of NADPH oxidase. All of these effects of LPS on HAECs were strongly inhibited by DFO. Exposing HAECs to 100 micromol/L iron (ferric citrate) for 48 hours exerted similar effects as LPS, and these effects were strongly inhibited by coincubation with DFO. Furthermore, neither LPS nor DFO affected mRNA and protein levels of p47phox a nonheme-containing, regulatory subunit of NADPH oxidase, or the mRNA level of NOX4, an isoform of the principal catalytic subunit of NADPH oxidase in endothelial cells. In contrast, heme oxygenase-1 was strongly suppressed by DFO, both in the absence and presence of LPS or iron.

CONCLUSIONS

Our data indicate that prolonged exposure to LPS or iron increases endothelial NADPH oxidase activity by increasing p22phox gene transcription and cellular levels of iron, heme, and p22phox protein. Iron chelation by DFO effectively suppresses endothelial NADPH oxidase activity, which may be helpful as an adjunct in reducing vascular oxidative stress and inflammation in atherosclerosis.

Relation of increased chromosomal damage to future adverse cardiac events in patients with known coronary artery disease

Somatic deoxyribonucleic acid (DNA) damage has been associated with early-phase and/or acute complications of atherosclerosis. However, it remains unclear whether circulating levels of DNA damage have prognostic value in patients with coronary artery disease (CAD). The aim of this study was to assess the prognostic significance of chromosomal DNA damage in human lymphocytes on the rate of major adverse cardiovascular events in patients with CAD. A follow-up prospective cohort study was carried out of 178 patients (153 men, mean age 61.9 +/- 9.7 years) with angiographically proved CAD who underwent micronucleus assay, a sensitive biomarker of chromosomal damage and genetic instability, from March 1999 and June 2001. During a mean follow-up period of 51.4 +/- 23.8 months, 58 patients had major adverse cardiovascular events (cardiac death, myocardial infarction, stroke, congestive heart failure, unstable angina, or coronary and peripheral revascularization). The overall event-free survival rates were 77.5%, 70.4%, and 49.0% in patients in the lower, middle, and upper tertiles of micronucleus level, respectively (log rank = 11.5, p = 0.003). In a multivariate Cox regression model, only the upper tertiles were significantly associated with a higher risk for major adverse cardiovascular events (hazard ratio 2.2, 95% confidence interval 1.1 to 4.7, p = 0.03). In conclusion, levels of peripheral chromosomal DNA damage may be a new sensitive biomarker of prognostic stratification in patients with known CAD.

Antioxidantes, atividade física e estresse oxidativo em mulheres idosas

OBJETIVO: Verificar a influência da suplementação de vitaminas antioxidantes na dieta de mulheres idosas que praticam exercícios físicos regulares, sobre o estresse oxidativo, indicadores da saúde física e risco de enfermidades cardiovasculares (ECV). MÉTODO: Foram observados dois grupos (S e C) de mulheres com idades entre 60 e 80 anos participantes de um programa de atividades físicas durante 58 semanas, com freqüência de três vezes por semana e duração de 50 a 55 minutos cada sessão. A dieta habitual do Grupo S (n=36) foi suplementada diariamente com 330 ml de uma bebida antioxidante (FuncionaTM); o Grupo C (n=32) ingeriu água e se caracterizou como controle. Como indicadores do estresse oxidativo foram determinadas as concentrações plasmáticas de glutationa reduzida (GSH) e oxidada (GSSG), calculada a relação molar GSH/GSSG, e identificado o dano oxidativo em lipídios e proteínas. As condições físicas e cardiovasculares foram avaliadas por meio dos parâmetros antropométricos habituais (peso, altura e índice de massa corporal) e da pressão arterial. RESULTADOS: O Grupo C apresentou aumentos significativos do estresse oxidativo, redução da pressão arterial e dos valores médios de indicadores de risco de ECV. O Grupo S teve o estresse oxidativo reduzido significativamente e apresentou incremento dos ganhos cardiovasculares. Não foram identificadas significâncias em relação aos efeitos ergogênicos. CONCLUSÃO: Os dados indicam que mulheres idosas que realizam exercícios físicos freqüentes melhoram suas condições físicas e cardiovasculares e que o suplemento dietético continuado de alimentos funcionais antioxidantes podem minimizar os efeitos danosos das espécies reativas de oxigênio.

Parenteral iron compounds: potent oxidants but mainstays of anemia management in chronic renal disease

Ferric iron (Fe)-carbohydrate complexes are widely used for treating Fe deficiency in patients who are unable to meet their Fe requirements with oral supplements. Intravenous Fe generally is well tolerated and effective in correcting Fe-deficient states. However, the complexing of Fe to carbohydrate polymers does not block its potent pro-oxidant effects; systemic free radical generation and, possibly, tissue damage may result. The purpose of this review is to (1) underscore the capacity of currently used parenteral Fe formulations to induce oxidative stress, (2) compare the severity of these oxidant reactions with those that result from unshielded Fe salts and with each other, and (3) speculate as to the potential of these agents to induce acute renal cell injury and augment systemic inflammatory responses. The experimental data that are reviewed should not be extrapolated to the clinical setting or be used for clinical decision making. Rather, it is hoped that the information provided herein may have utility for clinical hypothesis generation and, hence, future clinical studies. By so doing, a better understanding of Fe's potential protean effects on patients with renal disease may result.

Effects of basal level of antioxidants on oxidative DNA damage in humans

BACKGROUND

Vitamins A, E and C, and uric acid, which can scavenge free radicals should also protect DNA from the damage. It is reasonable to assume that agents that decrease oxidative DNA damage should also decrease subsequent cancer development.

AIM OF THE STUDY

A relationship between basal level of antioxidants (vitamins A, C and E and uric acid) and oxidative DNA damage was assessed. For the first time, the broad spectrum of oxidative DNA damage biomarkers: urinary excretion of 8-oxodG, 8-oxoGua and 5HMUra as well as the level of oxidative DNA damage in leukocytes was analyzed in healthy subjects (n = 158).

METHODS

Using HPLC prepurification/isotope dilution GC/MS methodology, we examined the amount of oxidative DNA damage products excreted into urine and the amount of 8-oxodG in leukocytes' DNA (with HPLC/EC technique). The level of antioxidant vitamins and uric acid was estimated by HPLC technique with fluorimetric and UV detection.

RESULTS

Analyses of relationship between the most common antioxidants (vitamins A, C, E and uric acid) and oxidative DNA damage products reveal weak, statistically significant negative correlation between retinol and all the measured parameters except 5HMUra. Vitamin C negatively correlates with urinary excretion of 8-oxodG and 8-oxoGua. Uric acid revealed statistically significant negative correlation with 8-oxodG in cellular DNA and urinary excretion of 5HMUra, while alpha-tocopherol correlates negatively only with 8-oxodG in cellular DNA. Good, significant (P < 0.0001), positive correlation (r = 0.61) was noted between urinary levels of the base, 8-oxoGua and the deoxynucleoside, 8-oxodG.

CONCLUSION

Our results suggest that oxidative DNA damage shows limited but significant response to antioxidants analyzed in this study and is more affected by many other cellular functions like antioxidant enzymes or DNA repair enzymes as well as genetics.

HFE mutations and risk of coronary heart disease in middle-aged women

BACKGROUND

Although heterozygosity for the C282Y mutation in the HFE gene has been associated with an increased risk of cardiovascular events, epidemiological studies remain inconclusive. The aim of the present study was to obtain further evidence as to whether HFE mutations are associated with risk of coronary heart disease (CHD) in middle-aged women. We used data of a cohort of 15 236 Dutch middle-aged women to investigate whether C282Y carriers and H63D carriers are at increased risk of coronary heart disease compared with non-carriers.

MATERIALS AND METHODS

Women were included in the study between 1993 and 1997 and were followed until 1 January 2000 for cardiovascular events. HFE genotyping was performed on all 211 coronary heart disease cases and a randomly selected sample from the baseline cohort (n = 1526). A weighted Cox proportional hazards model was used to estimate crude, age-adjusted and multivariate adjusted hazard ratios for C282Y and H63D carriership in relation to coronary heart disease.

RESULTS

Compared with non-carriers, those that carried the C282Y allele were not at increased risk for CHD (HR = 1.25, 95% CI = 0.74-2.09). Neither did we find an association between the H63D mutation and CHD risk (HR = 0.73, 95% CI = 0.43-1.24).

CONCLUSIONS

Our results are in accordance with similar studies to date, for which we present a meta-analysis. HFE mutations appear not to affect the risk of coronary heart disease.

Exercise, oxidative stress and risk of cardiovascular disease in the elderly. Protective role of antioxidant functional foods

Free radicals and oxidative stress are involved in the pathogenic mechanisms of cardiovascular disease (CVD), diabetes and cancer. Exercise is a useful strategy for preventing CVD but in elderly persons it can enhance oxidative stress, which is why some studies recommend antioxidant supplementation for exercising elderly subjects. This intervention study was performed on 320 elderly subjects following a Geriatric Revitalization Program (GEREPRO) to maintain physical health and reduce CVD risk. GEREPRO was based on regular exercise concurrent with a nutritional antioxidant treatment based on daily intake of a functional antioxidant food, Biofrutas. Sustained exercise (10 months, 3 sessions/week) significantly increased cardiorespiratory fitness and plasma HDL-cholesterol; it reduced some predictors of cardiovascular risk (arterial pressure, LDL-cholesterol, total cholesterol/LDL-C, LDL-C/HDL-C), but significantly enhanced some biomarkers of oxidative stress. Concurrent antioxidant supplementation did not produce any ergogenic effects but, meaningfully, enhanced some positive effects of exercise on physical health and the CDV risk index, and it totally prevented the exercise-induced oxidative stress. Our results show that regular and moderate exercise improves cardiorespiratory function and reduces CVD risk in elderly people, while concurrent antioxidant supplementation modulates oxidative insult during exercise in the elderly and enhances the beneficial effects of exercise.

Increased plasma malondialdehyde and protein carbonyl levels and lymphocyte DNA damage in patients with angiographically defined coronary artery disease

We investigated the oxidative modifications of lipids, proteins and DNA, three potential molecular targets of oxidative stress, in 30 patients with angiographically defined coronary artery disease (CAD) and 30 healthy control subjects. In addition, we examined relationships between these oxidative modifications and the severity of vascular lesions in patients with CAD. Malondialdehyde (MDA) and protein carbonyl (PC) levels, as well as ferric reducing antioxidant power (FRAP), were measured in the plasma. DNA damage was evaluated as single strand breaks (SSBs), formamidopyrimidine glycosylase (Fpg) and endonuclease III (E-III)-sensitive sites by the comet assay in DNA isolated from lymphocytes. MDA and PC levels increased, but FRAP values decreased, in patients as compared to controls. However, these values did not vary with the number of affected coronary vessels and were not correlated with Duke score, a parameter of the severity of vascular lesions in patients with CAD. We also found that lymphocyte DNA damage (SSBs, Fpg and E-III sites) were increased in patients. Although there were no significant differences in SSBs values in patients grouped according to affected vessel number, Fpg and E-III sites increased. We also detected significant correlations between Duke scores and SSBs and Fpg sites. Serum cholesterol, triglyceride and LDL-cholesterol levels were found to increase, but HDL-cholesterol levels decreased in CAD patients, but these lipids were not correlated with Duke scores. The results of this study reinforce the presence of increased combined oxidative modifications in lipid, protein and DNA in patients with CAD. However, lymphocyte DNA damage seems to be a more reliable assay than MDA and PC determinations to detect the severity of vascular lesions in patients.

Iron, oxidative stress and human health

The amount of iron within the cell is carefully regulated in order to provide an adequate level of the micronutrient while preventing its accumulation to toxic levels. Iron excess is believed to generate oxidative stress, understood as an increase in the steady state concentration of oxygen radical intermediates. The main aspects of cellular metabolism of iron, with special emphasis on the role of iron with respect to oxidative damage to lipid membranes, are briefly reviewed here. Both in vitro and in vivo models are examined. Finally, a discussion of iron overload and its impact on human health is included. Overall, further studies are required to assess more effective means to limit iron-dependent damage, by minimizing the formation and release of free radicals in tissues when the cellular iron steady state concentration is increased either as a consequence of disease or by therapeutic iron supplementation.

Oxidation of serum low-density lipoprotein (LDL) and antioxidant status in young and elderly humans

The incidence of atherosclerosis increases with age, as do various indices of free-radical mediated damage, e.g., lipid peroxidation. Because lipid peroxidation plays a prominent role in lipoprotein oxidation, likely a prelude to atherosclerosis, we compared the susceptibility of lipoproteins to oxidation in young (19-30 years) and elderly (59-86 years) groups. Although we found no significant differences in serum malondialdehyde (MDA) or oxidized LDL antibodies (OLAB) between young and elderly lipoproteins, MDA was directly related to OLAB regardless of age (r = 0.322, p = 0.005) and there was a trend for lower OLAB levels (30.5%, p = 0.079) in the elderly compared to the young population. Overall, serum antioxidant status was either similar or greater in the elderly group compared to the young group, likely reflecting antioxidant supplementation by the elderly group. OLAB was inversely related to Vitamin C (r = -0.310, p = 0.008) and Vitamin E intake (r = -0.277, p = 0.018) from foods and supplements. Serum levels of Vitamin C and Vitamin E were significantly higher (18.5%, p = 0.021 and 58.1 %, p < 0.001, respectively) in the elderly group compared to the young group and the ratio of Vitamin E to Vitamin C was significantly higher (30.4%, p = 0.042) in the serum of the elderly group. Oxidation of serum LDL and antioxidant status were not affected by age; however, the ratio of serum Vitamin E to Vitamin C was higher in the elderly group which may affect Vitamin E recycling.

Exposure to chronic noise and fractionated X-ray radiation elicits biochemical changes and disrupts body weight gain in rat

The aim was to assess the developmental and biochemical effects resulting from separate and combined exposures to radiation and noise in adult male Sprague-Dawley rats. For 21 days, animals were exposed daily (1) to whole-body 121 kVp X-ray exposure (cumulative dose=5 Gy), (2) to random intermittent noise band-limited between 0.4 and 20 kHz; 2 h day(-1) 86 decibels (dB) and (3) to combined exposures. Control animals were housed under ambient noise conditions 55 dB A-weighted (dBA) and sham-exposed to X-rays. Body weight gain was significantly reduced in animals exposed to either X-rays or noise, and the loss was more pronounced in animals exposed to both conditions. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone was altered by the treatment conditions. This study corroborated previous reports that ionizing radiation exposure increased plasma levels of 8-hydroxy-2'-deoxyguanosine (8-OHDG), but no effect was observed in animals co-exposed to chronic noise. Plasma big-endothelin-1 (Big ET-1) was significantly reduced in animals exposed to a combination of noise and X-rays. The results indicated that (1) adaptation to chronic noise appeared to occur at the level of the hypothalamic pituitary adrenal (HPA) response, in spite of a compromise in overall body weight gain; and (2) ionizing radiation exposure might alter systems activated by stressor exposure and/or act independently to influence health outcomes.

Oxidative DNA damage and antioxidant vitamin level: comparison among lung cancer patients, healthy smokers and nonsmokers

In the present study, we examined whether the level of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in leukocyte DNA is higher in lung cancer patients compared to controls. Factors that may influence oxidative stress, such as antioxidant vitamins, were also determined. These parameters were analyzed in 4 groups of subjects: smokers with lung cancer, ex-smokers with lung cancer, healthy smokers with comparable smoking status and healthy nonsmokers. The 8-oxodGuo mean level in leukocytes of lung cancer patients reached values of 9.22/10(6) dGuo molecules (smokers) and 11.16/10(6) dGuo molecules (ex-smokers). These values were significantly higher than in DNA of healthy smokers and nonsmokers, where mean levels reached 6.99/10(6) dGuo molecules and 5.98/10(6) dGuo molecules, respectively. Mean levels of vitamin C in the plasma of controls and lung cancer patients were 56.17 microM (nonsmokers), 26.34 microM (healthy smokers), 23.83 microM (cancer patients, smokers) and 29.19 microM (cancer patients, ex-smokers). The difference between nonsmokers and the 3 other groups was statistically significant. Vitamin E level was significantly reduced in the plasma of cancer patients (smokers 19.94 microM, ex-smokers 19.59 microM) compared to healthy smokers (28.93 microM). No changes in vitamin A concentration were found. Our results suggest that a high level of 8-oxodGuo in leukocyte DNA and a low concentration of vitamin E in the blood may predict lung cancer risk. However, it is also possible that these phenomena may simply result from disease development.

Oxidative stress in atherogenesis and arterial thrombosis: the disconnect between cellular studies and clinical outcomes

Atherosclerosis is a multifactorial disease for which the molecular etiology of many of the risk factors is still unknown. As no single genetic marker or test accurately predicts cardiovascular death, phenotyping for markers of inflammation may identify the individuals at risk for vascular diseases. Reactive oxygen species (ROS) are key mediators of signaling pathways that underlie vascular inflammation in atherogenesis, starting from the initiation of fatty streak development through lesion progression to ultimate plaque rupture. Various animal models of atherosclerosis support the notion that ROS released from NAD(P)H oxidases, xanthine oxidase, lipoxygenases, and enhanced ROS production from dysfunctional mitochondrial respiratory chain indeed have a causatory role in atherosclerosis and other vascular diseases. Human investigations also support the oxidative stress hypothesis of atherogenesis. This is further supported by the observed impairment of vascular function and enhanced atherogenesis in animal models that have deficiencies in antioxidant enzymes. The importance of oxidative stress in atherosclerosis is further emphasized because of its role as a unifying mechanism across many vascular diseases. The main contraindicator for the role oxidative stress plays in atherosclerosis is the lack of effectiveness of antioxidants in reducing primary endpoints of cardiovascular death and morbidity. However, this lack of effectiveness by itself does not negate the existence or causatory role of oxidative stress in vascular disease. Lack of proven markers of oxidative stress, which could help to identify a subset of population that can benefit from antioxidant supplementation, and the complexity and subcellular localization of redox reactions, are among the factors responsible for the mixed outcomes in the use of antioxidants for the prevention of cardiovascular diseases. To better understand the role of oxidative stress in vascular diseases, future studies should be aimed at using advances in mouse and human genetics to define oxidative stress phenotypes and link phenotype with genotype.

Dietary haem iron and coronary heart disease in women

AIMS

A role for iron in the risk of ischaemic heart disease has been supported by in vitro and in vivo studies. We investigated whether dietary haem iron intake is associated with coronary heart disease (CHD) risk in a large population-based cohort of middle-aged women.

METHODS AND RESULTS

We used data of 16 136 women aged 49-70 years at recruitment between 1993 and 1997. Follow-up was complete until 1 January 2000 and 252 newly diagnosed CHD cases were documented. Cox proportional hazards analysis was used to estimate hazard ratios of CHD for quartiles of haem iron intake, adjusted for cardiovascular and nutritional risk factors. We stratified by the presence of additional cardiovascular risk factors, menstrual periods, and antioxidant intake to investigate the possibility of effect modification. High dietary haem iron intake was associated with a 65% increase in CHD risk [hazard ratio (HR)=1.65; 95% confidence interval (CI): 1.07-2.53], after adjustment for cardiovascular and nutritional risk factors. This risk was not modified by additional risk factors, menstruation, or antioxidant intake.

CONCLUSION

The results indicate that middle-aged women with a relatively high haem iron intake have an increased risk of CHD.

Parenteral iron compounds sensitize mice to injury-initiated TNF-alpha mRNA production and TNF-alpha release

Intravenous Fe is widely used to treat anemia in renal disease patients. However, concerns of potential Fe toxicity exist. To more fully define its spectrum, this study tested Fe's impact on systemic inflammation following either endotoxemia or the induction of direct tissue damage (glycerol-mediated rhabdomyolysis). The inflammatory response was gauged by tissue TNF-alpha message expression and plasma TNF-alpha levels. CD-1 mice received either intravenous Fe sucrose, -gluconate, or -dextran (FeS, FeG, or FeD, respectively; 2 mg), followed by either endotoxin (LPS) or glycerol injection 0-48 h later. Plasma TNF-alpha was assessed by ELISA 2-3 h after the LPS or glycerol challenge. TNF-alpha mRNA expression (RT-PCR) was measured in the kidney, heart, liver, lung, and spleen with Fe +/- LPS treatment. Finally, the relative impacts of intramuscular vs. intravenous Fe and of glutathione (GSH) on Fe/LPS- induced TNF-alpha generation were assessed. Each Fe preparation significantly enhanced LPS- or muscle injury-mediated TNF-alpha generation. This effect was observed for at least 48 h post-Fe injection, a time at which plasma iron levels were increased by levels insufficient to fully saturate transferrin. Fe did not independently increase plasma TNF-alpha or tissue mRNA. However, it potentiated postinjury-induced TNF-alpha mRNA increments and did so in an organ-specific fashion (kidney, heart, and lung; but not in liver or spleen). Intramuscular administration, but not GSH treatment, negated Fe's ability to synergize LPS-mediated TNF-alpha release. We conclude 1) intravenous Fe can enhance TNF-alpha generation during LPS- or glycerol-induced tissue damage; 2) increased TNF-alpha gene transcription in the kidney, heart, and lung may contribute to this result; and 3) intramuscular administration, but not GSH, might potentially mitigate some of Fe's systemic toxic effects.

Oxidative DNA damage and disease: induction, repair and significance

The generation of reactive oxygen species may be both beneficial to cells, performing a function in inter- and intracellular signalling, and detrimental, modifying cellular biomolecules, accumulation of which has been associated with numerous diseases. Of the molecules subject to oxidative modification, DNA has received the greatest attention, with biomarkers of exposure and effect closest to validation. Despite nearly a quarter of a century of study, and a large number of base- and sugar-derived DNA lesions having been identified, the majority of studies have focussed upon the guanine modification, 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-OH-dG). For the most part, the biological significance of other lesions has not, as yet, been investigated. In contrast, the description and characterisation of enzyme systems responsible for repairing oxidative DNA base damage is growing rapidly, being the subject of intense study. However, there remain notable gaps in our knowledge of which repair proteins remove which lesions, plus, as more lesions identified, new processes/substrates need to be determined. There are many reports describing elevated levels of oxidatively modified DNA lesions, in various biological matrices, in a plethora of diseases; however, for the majority of these the association could merely be coincidental, and more detailed studies are required. Nevertheless, even based simply upon reports of studies investigating the potential role of 8-OH-dG in disease, the weight of evidence strongly suggests a link between such damage and the pathogenesis of disease. However, exact roles remain to be elucidated.

Parenteral iron nephrotoxicity: Potential mechanisms and consequences1

BACKGROUND

Parenteral iron administration is a mainstay of anemia management in renal disease patients. However, concerns of potential iron toxicity persist. Thus, this study was conducted to more fully gauge iron toxicologic profiles and potential determinants thereof.

METHODS

Isolated mouse proximal tubule segments (PTS) or cultured proximal tubular [human kidney (HK-2)] cells were exposed to four representative iron preparations [iron sucrose (FeS), iron dextran (FeD), iron gluconate (FeG), or iron oligosaccharide (FeOS)] over a broad dosage range (0, 30 to 1000 microg iron/mL). Cell injury was assessed by lactate deyhdrogenase (LDH) release, adenosine triphosphate (ATP) reductions, cell cytochrome c efflux, and/or electron microscopy. In vivo toxicity (after 2 mg intravenous iron injections) was assessed by plasma/renal/cardiac lipid peroxidation [malondialdehyde (MDA)], renal ferritin (protein)/heme oxygenase-1 (HO-1) (mRNA) expression, electron microscopy, or postiron injection PTS susceptibility to attack.

RESULTS

In each test, iron evoked in vitro toxicity, but up to 30x differences in severity (e.g., ATP declines) were observed (FeS > FeG > FeD = FeOS). The in vitro differences paralleled degrees of cell (HK-2) iron uptake. In vivo correlates of iron toxicity included variable increases in renal MDA, ferritin, and HO-1 mRNA levels. Again, these changes appeared to parallel in vivo (glomerular) iron uptake (seen with FeS and FeG, but not with FeD or FeOS). Iron also effected in vivo alterations in proximal tubule cell homeostasis, as reflected by the "downstream" emergence of tubule resistance to in vitro oxidant attack.

CONCLUSION

Parenteral iron formulations have potent, but highly variable, cytotoxic potentials which appear to parallel degrees of cell iron uptake (FeS > FeG >> FeD or FeOS). That in vitro injury can be expressed at clinically relevant iron concentrations, and that in vivo glomerular iron deposition/injury may result, suggest caution is warranted if these agents are to be administered to patients with active renal disease.

Obesity Exacerbates Oxidative Stress Levels after Acute Exercise

INTRODUCTION/PURPOSE

This study compared oxidative stress levels and antioxidant capacity in nonobese and obese participants after acute resistance (RX) and aerobic exercise (AX).

METHODS

Blood samples were collected from 28 nonobese (mean = 20.8% body fat) and obese (mean = 35.0% body fat) participants pre- and immediately post-RX and AX. Lipid hydroperoxides (PEROX), malondialdehyde (TBARS) and total antioxidant status (TAS) were measured. Oxygen consumption (VO2) and minute ventilation (VE) values were determined during each exercise session.

RESULTS

In both groups, PEROX and TBARS were elevated post-RX and AX, with the greater elevations occurring in the obese group in each case (P < 0.05). In the obese, TBARS increased by 42% and 41% post-RX and AX, respectively, compared with 7.1% and 26.9% in the nonobese group. PEROX increased by 100% and 70% post-RX and AX, respectively, in the obese, and by 85% and 62% in the nonobese. TAS was 17% higher (P < 0.05) post-RX in the nonobese compared with the obese, whereas TAS values were not different post-AX. Peak and average VE, and relative VO2). rates were higher in the obese post-AX compared with the nonobese (P < 0.05) Correlations existed between the exercise-induced change in PEROX and body fat, vitamin C and A intake, peak oxygen consumption, and exercise ventilation rates in the obese group (r = 0.784-0.776, P < 0.05). In both groups, the exercise-induced changes in PEROX were associated with vitamin C intake, exercise ventilation rates, VO2peak, and plasma triglycerides (r = 0.669-0.558, P < 0.05).

CONCLUSION

Lipid peroxidation is elevated in both RX and AX, and it is exacerbated in the obese. The mechanisms underlying this response in each exercise may be different but could involve plasma triglycerides, oxygen consumption, and antioxidant intake.

Effects of homocysteine on apoptosis-related proteins and anti-oxidant systems in isolated human lymphocytes

Homocysteine (Hcy) is a nonprotein-forming sulphur amino acid that plays an important role in remethylation and trans-sulphuration processes. In recent years, it has been suggested that increased levels of plasma Hcy may play a role in the pathogenesis of various diseases, particularly at the cardiovascular level. The pathogenic mechanism of hyperhomocysteinemia, however, has not been clarified. Because oxygen radicals can be generated by the auto-oxidation of this amino acid, it has been suggested that Hcy may cause cellular damage through oxidative mechanisms, ultimately leading to apoptotic cell death. In this study, we sought to investigate the effects of Hcy on oxidative damage and antioxidant agent levels, as well as on apoptosis-related proteins and apoptosis occurrence in human cells. For this purpose, we measured levels of Bcl-2, caspase-3 and caspase-9 activity, Cu/Zn superoxide dismutase, reduced glutathione, lipid peroxidation [malondialdehyde and 4-hydroxy-2 (E)-nonenal concentrations], apoptotic single-stranded DNA and nuclear changes in human isolated lymphocytes exposed to increasing concentrations of Hcy. Incubation with Hcy did not induce significant changes in any of these biomarkers. Therefore, our results do not support the existence of a direct link between increased levels of Hcy and the occurrence of a pro-apoptotic state mediated by enhanced oxidative stress.

Age-related changes of serum lipoprotein oxidation in rats

Oxidation of low-density lipoprotein (LDL) may be a prelude to atherogenesis and directly age related. To assess whether there may be relationship between age and plasma lipoprotein (LP) oxidation, we studied copper-mediated LP oxidation isolated from the blood of 2 months, 7 months, and 15 months old rats. We determined whether the susceptibility of LP to oxidation might be related to vitamin C levels in serum, vitamin E levels in LP, or the total antioxidant capacity (TAC) of serum or LP. Serum vitamin C content was inversely related to age, malondialdehyde (MDA) propagation rate, and maximum change of MDA concentrations. However, there were no significant relationships between age and serum TAC, LP TAC, serum vitamin E, or the ratio of LP vitamin E to serum vitamin C content. The lag phase of MDA formation was significantly decreased with age and the ratio of LP vitamin E content to serum vitamin C content, increased with age. Maximum change of MDA concentration was positively correlated with the ratio of LP vitamin E contents to serum vitamin C concentration. Thus, as the rat ages, vitamin C status decreases with an increased LP susceptibility to oxidation. It is tempting to speculate that enhanced LP oxidation in older rats may reflect a reduced amount of recycling of LDL vitamin E by serum vitamin C.

Red blood cells upregulate cytoprotective proteins and the labile iron pool in dividing human T cells despite a reduction in oxidative stress

We have recently reported that red blood cells (RBC) promote T cell growth and survival by inhibiting activation-induced T cell death. In the present study, we have examined parameters of oxidative stress and intracellular iron in activated T cells and correlated these data with the expression of ferritin, heme oxygenase-1 (HO-1), and the transferrin receptor CD71. T cells growing in the presence of RBC had reduced levels of reactive oxygen species (ROS) and oxidatively modified proteins, suggesting that RBC efficiently counteracted ROS production on the activated T cells. Flow cytometry and immunodetection demonstrated that T cells dividing in the presence of RBC had increased levels of intracellular ferritin rich in L-subunits and HO-1 along with a downmodulation in CD71 expression. Finally, using the fluorescent iron indicator calcein and flow cytometry analysis, we were able to show that a relative amount of the labile iron pool (LIP) was upregulated in T cells growing in the presence of RBC. These findings are consistent with a typical response to iron overload. However, neither heme compounds nor ferric iron reproduced the levels of expansion and survival of T cells induced by intact RBC. Altogether, these data suggest that RBC inhibit apoptosis of activated T cells by a combination of ROS scavenging and upregulation of cytoprotective proteins such as ferritin and HO-1, which may counteract a possible toxic effect of the increased intracellular free iron.