Smoking is associated with alterations of blood thiol-group related antioxidants in patients on hemodialysis

Oxidative stress in hemodialysis: Causative mechanisms, clinical implications, and possible therapeutic interventions

Oxidative stress (OS) is the result of prooxidant molecules overwhelming the antioxidant defense mechanisms. Hemodialysis (HD) constitutes a state of elevated inflammation and OS, due to loss of antioxidants during dialysis and activation of white blood cells triggering production of reactive oxygen species. Dialysis vintage, dialysis methods, and type and condition of vascular access, biocompatibility of dialyzer membrane and dialysate, iron administration, and anemia all can play a role in aggravating OS, which in turn has been associated with increased morbidity and mortality. Oral or intravenous administration of antioxidants may detoxify the oxidative molecules and at least in part repair OS-mediated tissue damage. Lifestyle interventions and optimization of a highly biocompatible HD procedure might ameliorate OS development in dialysis.

An association of smoking with serum urate and gout: A health paradox

BACKGROUND

The potential effect of cigarette smoking on levels of serum urate and risk of gout has been considered by a large number of studies, either as the primary variable of interest or as a covariate.

METHODS

Here we systematically review the published evidence relating to the relationship of smoking with serum urate, hyperuricaemia, and gout.

RESULTS

Many studies have reported that smoking reduces serum urate, however, the evidence has not been conclusive with other studies pointing to the opposite or no effect. It has also been suggested that smoking reduces the risk of gout, although there is some evidence to contradict this finding.

CONCLUSION

A consensus has yet to be reached as to the effect of smoking on serum urate levels and the risk of gout.

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Oxidative Stress and Antioxidant Capacity in Smoking and Nonsmoking Men With HIV/Acquired Immunodeficiency Syndrome

BACKGROUND

Past studies document decreased levels of antioxidants and selenium and increased levels of oxidative stress in people living with HIV/acquired immunodeficiency syndrome (AIDS). Cigarette smoking is another source of oxidative stress. Excessive oxidative stress can induce HIV replication, resulting in disease progression. The purpose of this study was to determine whether subjects with HIV/AIDS who smoke cigarettes have increased oxidative stress and decreased antioxidant status compared with nonsmokers with HIV/AIDS.

METHODS

Thirty-one men with HIV/AIDS (adhering to highly active antiretroviral therapy for the previous 3 months) were recruited during regular visits to a Veterans Affairs Medical Center Infectious Disease Clinic in a southeastern US city. Plasma was obtained from a 1-time blood draw for this comparison study. Plasma lipid peroxide (LPO) was used as a marker of oxidative stress. Indicators of antioxidant capacity included plasma glutathione peroxidase (GPx, the functional indicator of selenium status), vitamin C, and antioxidant potential (AOP).

RESULTS

Fifteen smokers and 10 nonsmokers with HIV/AIDS were enrolled. Median plasma LPO level was above the normal range of 0-1.3 micromol/L in both nonsmokers (2.5 [0-23.4] micromol/L, median [range]) and smokers (4.0 [0-47.5] micromol/L), but there was no difference between groups. Plasma GPx concentration was significantly lower in smokers (169 [118-295] mumol/min/L) compared with nonsmokers (197 [149-414] micromol/min/L). Vitamin C and AOP levels were not different between groups.

CONCLUSIONS

This pilot study suggests that effects of smoking on oxidative stress are not additive, as no striking differences were observed in oxidative stress or antioxidant capacity between clinically stable smoking and nonsmoking men with HIV/AIDS.

[Smoking cessation in case of chronic kidney disease]

Smoking is one of the main causes of morbidity and mortality around the world. In France, despite increase of cost of cigarettes and exclusion of smoking in public places, daily smoking consummation remains high, particularly in women and young. Now, smoking is considered as a compartmental and/or psychologic and/or physic addiction. There are many categories of smokers and smoking cessation strategies must be tailored to individual level. Whatever the etiology of chronic kidney disease, in dialysis patient as transplanted, hypertension and vascular diseases are strong determinants of prognosis. In this way, there is a need for stronger involvement of nephrologists in the process of smoking cessation of their patients. Therapeutics and strategies are reviewed.

Cysteine/cystine redox signaling in cardiovascular disease

Extracellular thiol/disulfide redox environments are highly regulated in healthy individuals. The major thiol/disulfide redox couple in human plasma is cysteine (Cys) and its disulfide form, cystine (CySS). Oxidation of this redox couple, measured as a more positive steady-state redox potential (E(h)), is associated with risk factors for cardiovascular disease (CVD), including aging, smoking, obesity, and alcohol abuse. Rodent and vascular cell studies show that the extracellular redox state of Cys/CySS (E(h)CySS) can play a vital role in controlling CVD through proinflammatory signaling. This inflammatory signaling is regulated by cell-surface protein redox state and involves mitochondrial oxidation, nuclear factor-κB activation, and elevated expression of genes for monocyte recruitment to endothelial cells. Gene array and proteomics studies reveal the global nature of redox effects, and different cell types, e.g., endothelial cells, monocytes, fibroblasts, and epithelial cells, show cell-specific redox responses with different phenotypic traits, e.g., proliferation and apoptosis, which can contribute to CVD. The critical nature of the proinflammatory redox signaling and cell biology associated with E(h)CySS supports the use of plasma levels of Cys, CySS, and E(h)CySS as key indicators of vascular health. Plasma redox-state-based pharmacologic interventions to control or improve E(h)CySS may be effective in preventing CVD onset or progression.

Ameliorative effect of caffeic acid phenethyl ester on histopathological and biochemical changes induced by cigarette smoke in rat kidney

It was aimed to investigate the histopathological and biochemical changes in kidney tissues of rats exposed to cigarette smoke and possible protective effects of caffeic acid phenethyl ester (CAPE) on these changes. Twenty one male Wistar albino rats were divided into three equal groups. Animals in group I were used as control. Rats in group II were exposed to cigarette smoke and rats in group III were exposed to cigarette smoke and daily administration of CAPE. At the end of the 60-day experimental period, all the animals were sacrificed by decapitation. The serum samples obtained from the animals were studied for uric acid, creatinine and blood urine nitrogen (BUN) levels. Following routine histological procedures, kidney tissue specimens were examined under a light microscope. In addition, dismutase (SOD) and glutathione peroxidase (GSH-Px) enzyme activities and malondialdehyde (MDA) and nitric oxide (NO) contents were determined spectrophotometrically in tissue samples. It was found that serum uric acid and BUN levels of the rats exposed to cigarette smoke alone were elevated, although serum creatinine levels did not significantly change. Furthermore, renal SOD, GSH-Px, NO and MDA levels were significantly increased. These increases in serum BUN, and renal SOD, GSH-Px, NO and MDA levels were significantly inhibited by CAPE treatment. In light microscopic observations of tissues from rats exposed to smoke, mesangial cell proliferation in the renal corpuscles, dilatation and congestion in the peritubular capillaries and degenerative alterations in the proximal tubules were noted. There were also atrophic renal corpuscles. However, these histopathological changes were partially disappeared in the rats exposed to cigarette smoke plus CAPE. The present findings indicate that cigarette smoke causes impairment in renal structure and function, which can be prevented by CAPE administration.

Endothelial function and aminothiol biomarkers of oxidative stress in healthy adults

Endothelial dysfunction is known to precede the development of atherosclerosis and results primarily from increased oxidative degradation of NO. We hypothesized that assessment of oxidative stress in the bloodstream will reliably predict endothelial function in healthy adults. A total of 124 healthy nonsmokers had endothelial function assessed using ultrasound measurement of brachial artery flow-mediated vasodilation. Plasma oxidative stress was estimated by measuring the levels of the reduced and oxidized forms of thiols, including glutathione (reduced glutathione and oxidized glutathione) and cysteine (cysteine and cystine), respectively, and the mixed disulfide. Among the traditional risk factors, there were significant and independent correlations between flow-mediated vasodilation and high-density lipoprotein level, body mass index, gender, and the Framingham risk score. Among the thiol markers, plasma cystine (r=-0.23; P=0.009) and the mixed disulfide (r=-0.23; P=0.01) levels correlated with endothelium-dependent but not endothelium-independent vasodilation, even after adjusting for the Framingham risk score and high-sensitivity C-reactive protein level. A higher level of oxidized metabolites was associated with worse endothelial function. In conclusion, the oxidative stress markers, cystine, and the mixed disulfide are independent predictors of endothelial function. These markers, in combination with the Framingham risk score, may help in the early identification of asymptomatic subjects with endothelial dysfunction who are at potentially increased risk for future atherosclerotic disease progression.

Malondialdehyde as biomarker of oxidative damage to lipids caused by smoking

Thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) have been used as biomarkers of lipid oxidation for more than thirty years. The validity of these biomarkers has been rightfully criticized for a lack of specificity and problems with post sampling formation. Numerous assays have been published for their analysis giving rise to reference intervals for healthy non-smoking humans varying more than to orders of magnitude. In spite of these problems, these biomarkers remain among the most commonly reported indices of oxidative damage and the present review focuses on the problems associated with MDA/TBARS analysis, their potential as biomarkers of oxidative stress and the effect of smoking on MDA status.

The relationship between plasma levels of oxidized and reduced thiols and early atherosclerosis in healthy adults

OBJECTIVES

The study investigated the relationship between biomarkers of oxidative stress and early atherosclerosis.

BACKGROUND

Oxidative stress is an important etiologic factor in the pathogenesis of vascular disease. We hypothesized that oxidative stress would predict early atherosclerosis in a relatively healthy population.

METHODS

One hundred fourteen healthy non-smokers, without known clinical atherosclerosis, had carotid intima-media thickness (IMT) measured using ultrasound. Oxidative stress was estimated by measuring plasma levels of: 1) glutathione (GSH), an important intracellular antioxidant thiol, its oxidized disulfide form (GSSG), and their redox state (E(h) GSH/GSSG), and 2) cysteine (Cys), an important extracellular antioxidant thiol, its oxidized disulfide form cystine (CySS), and their redox state (E(h)Cys/CySS).

RESULTS

The univariate predictors of IMT were age, body mass index, low-density lipoprotein cholesterol, triglycerides, high-density lipoprotein cholesterol, high-sensitivity C-reactive protein (hs-CRP), and Framingham risk score. Intima-media thickness was also higher in males and hypertensive subjects. Among the oxidative stress markers, GSH (r = -0.39, p < 0.0001), CySS (r = 0.18, p = 0.049), and E(h) GSH/GSSG (r = 0.34, p < 0.0002) correlated with IMT. After adjusting for traditional risk factors and hs-CRP, only E(h) GSH/GSSG remained an independent predictor of IMT. E(h) GSH/GSSG predicted IMT in a manner that was both independent of and additive to Framingham risk score.

CONCLUSIONS

Glutathione redox state (E(h) GSH/GSSG), an in vivo measure of intracellular oxidative stress, is an independent predictor for the presence of early atherosclerosis in an otherwise healthy population. This finding supports a role for oxidative stress in the pathogenesis of premature atherosclerosis, and its measurement may help in the early identification of asymptomatic subjects at risk of atherosclerotic disease.