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

Dietary Antioxidants and Lung Cancer Risk in Smokers and Non-Smokers

Smoking is considered a major risk factor in the development of lung diseases worldwide. Active smoking and secondhand (passive) smoke (SHS) are related to lung cancer (LC) risk. Oxidative stress (OS) and/or lipid peroxidation (LP) induced by cigarette smoke (CS) are found to be involved in the pathogenesis of LC. Meta-analyses and other case-control/prospective cohort studies are inconclusive and have yielded inconsistent results concerning the protective role of dietary vitamins C and E, retinol, and iron intake against LC risk in smokers and/or non-smokers. Furthermore, the role of vitamins and minerals as antioxidants with the potential in protecting LC cells against CS-induced OS in smokers and non-smokers has not been fully elucidated. Thus, this review aims to summarize the available evidence reporting the relationships between dietary antioxidant intake and LC risk in smokers and non-smokers that may be used to provide suggestions for future research.

Oxidatively Damaged Nucleic Acid: Linking Diabetes and Cancer

Significance: Our current knowledge of the mechanism between diabetes and cancer is limited. Oxidatively damaged nucleic acid is considered a critical factor to explore the connections between these two diseases. Recent Advances: The link between diabetes mellitus and cancer has attracted increasing attention in recent years. Emerging evidence supports that oxidatively damaged nucleic acid caused by an imbalance between reactive oxygen species generation and elimination is a bridge connecting diabetes and cancer. 8-Oxo-7,8-dihydro-2'-deoxyguanosine and 8-oxo-7,8-dihydroguanosine assume important roles as biomarkers in assessing the relationship between oxidatively damaged nucleic acid and cancer. Critical Issues: The consequences of diabetes are extensive and may lead to the occurrence of cancer by influencing a combination of factors. At present, there is no direct evidence that diabetes causes cancer by affecting a single factor. Furthermore, the difficulty in controlling variables and differences in detection methods lead to poor reliability and repeatability of results, and there are no clear cutoff values for biomarkers to indicate cancer risk. Future Directions: A better understanding of connections as well as mechanisms between diabetes and cancer is still needed. Both diabetes and cancer are currently intractable diseases. Further exploration of the specific mechanism of oxidatively damaged nucleic acid in the connection between diabetes and cancer is urgently needed. In the future, it is necessary to further take oxidatively damaged nucleic acid as an entry point to provide new ideas for the diagnosis and treatment of diabetes and cancer. Experimental drugs targeting the repair process of oxidatively generated damage require an extensive preclinical evaluation and could ultimately provide new treatment strategies for these diseases. Antioxid. Redox Signal. 37, 1153-1167.

Surface-enhanced Raman spectroscopy for comparison of serum samples of typhoid and tuberculosis patients of different stages

BACKGROUND

Surface-enhanced Raman spectroscopy (SERS) is a reliable tool for the identification and differentiation of two different human pathological conditions sharing the same symptomology, typhoid and tuberculosis (TB).

OBJECTIVES

To explore the potential of surface-enhanced Raman spectroscopy for differentiation of two different diseases showing the same symptoms and analysis by principal component analysis (PCA) and partial least square discriminate analysis (PLS-DA).

METHODS

Serum samples of clinically diagnosed typhoid and tuberculosis infected individuals were analyzed and differentiated by SERS using silver nanoparticles (Ag NPs) as a SERS substrate. For this purpose, the collected serum samples were analyzed under the SERS instrument and unique SERS spectra of typhoid and tuberculosis were compared showing notable spectral differences in protein, lipid and carbohydrates features. Different stages of the diseased class of typhoid (Early acute and late acute stage) and tuberculosis (Pulmonary and extra-pulmonary stage) were compared with each other and with healthy human serum samples, which were significantly separated. Moreover, SERS data was analyzed using multivariate data analysis techniques including principal component analysis (PCA) and partial least square discriminate analysis (PLS-DA) and differences were so prominent to observe.

RESULTS

SERS Spectral data of typhoid and tuberculosis showed clear differences and were significantly separated using PCA. SERS spectral data of both stages of typhoid and tuberculosis were separated according to 1st principle component. Moreover, by analyzing data using partial least square discriminate analysis, differentiation of two disease classes were considered more valid with a 100% value of sensitivity, specificity and accuracy.

CONCLUSION

SERS can be employed for identification and comparison of two different human pathological conditions sharing same symptomology.

Relationships among smoking, oxidative stress, inflammation, macromolecular damage, and cancer

Smoking is a major risk factor for a variety of diseases, including cancer and immune-mediated inflammatory diseases. Tobacco smoke contains a mixture of chemicals, including a host of reactive oxygen- and nitrogen species (ROS and RNS), among others, that can damage cellular and sub-cellular targets, such as lipids, proteins, and nucleic acids. A growing body of evidence supports a key role for smoking-induced ROS and the resulting oxidative stress in inflammation and carcinogenesis. This comprehensive and up-to-date review covers four interrelated topics, including 'smoking', 'oxidative stress', 'inflammation', and 'cancer'. The review discusses each of the four topics, while exploring the intersections among the topics by highlighting the macromolecular damage attributable to ROS. Specifically, oxidative damage to macromolecular targets, such as lipid peroxidation, post-translational modification of proteins, and DNA adduction, as well as enzymatic and non-enzymatic antioxidant defense mechanisms, and the multi-faceted repair pathways of oxidized lesions are described. Also discussed are the biological consequences of oxidative damage to macromolecules if they evade the defense mechanisms and/or are not repaired properly or in time. Emphasis is placed on the genetic- and epigenetic alterations that may lead to transcriptional deregulation of functionally-important genes and disruption of regulatory elements. Smoking-associated oxidative stress also activates the inflammatory response pathway, which triggers a cascade of events of which ROS production is an initial yet indispensable step. The release of ROS at the site of damage and inflammation helps combat foreign pathogens and restores the injured tissue, while simultaneously increasing the burden of oxidative stress. This creates a vicious cycle in which smoking-related oxidative stress causes inflammation, which in turn, results in further generation of ROS, and potentially increased oxidative damage to macromolecular targets that may lead to cancer initiation and/or progression.

Low Vitamin C Status in Patients with Cancer Is Associated with Patient and Tumor Characteristics

Vitamin C (ascorbate) acts as an antioxidant and enzyme cofactor, and plays a vital role in human health. Vitamin C status can be affected by illness, with low levels being associated with disease due to accelerated turnover. However, robust data on the ascorbate status of patients with cancer are sparse. This study aimed to accurately measure ascorbate concentrations in plasma from patients with cancer, and determine associations with patient or tumor characteristics. We recruited 150 fasting patients with cancer (of 199 total recruited) from two cohorts, either prior to cancer surgery or during cancer chemo- or immunotherapy. A significant number of patients with cancer had inadequate plasma ascorbate concentrations. Low plasma status was more prevalent in patients undergoing cancer therapy. Ascorbate status was higher in women than in men, and exercising patients had higher levels than sedentary patients. Our study may prompt increased vigilance of ascorbate status in cancer patients.

Oxidative stress in lung cancer patients is associated with altered serum markers of lipid metabolism

In lung cancer (LC), alterations in redox balance are extensively observed and are a consequence of disease as well as co-occurrent with smoking. We previously demonstrated that metabolic disturbances such as trace element status and carbohydrate metabolism alterations are linked with redox status. The aim of this study was to evaluate relationships between the serum parameters of lipid metabolism and redox balance in LC patients. Serum parameters of lipid metabolism, i.e. total cholesterol (T-C), HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), triglycerides (TG), T-C:HDL-C ratio, non-HDL-C, apolipoprotein A1 (Apo-A1), apolipoprotein B (Apo-B) and Apo-B:Apo-A1 ratio, as well as systemic redox status, i.e. total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), vitamin E (VE), vitamin C (VC), malonyldialdehyde (MDA), conjugated dienes (CD), and 4-hydroxynonenal (4-HNE) were determined in 92 LC patients and 82 control subjects (CS). LC women had significantly lower T-C and LDL-C, and higher TG, while HDL-C, Apo-A1 and Apo-B were significantly decreased in LC patients regardless of sex, when compared to CS. LC men had alterations in the systemic total redox balance such as lower TAS and higher OSI than CS men. LC women had lower VC, but VE was decreased in LC patients, regardless of sex. We observed higher lipid peroxidation in LC patients expressed via higher 4-HNE and CD. Systemic redox disturbances were associated with serum lipid alterations: TOS and OSI were positively correlated with T-C:HDL-C ratio and Apo-B:Apo-A1 ratio and negatively with HDL-C. The parameters of lipid peroxidation CD and MDA were significantly associated with variables reflecting lipid disturbances. The observed correlations were strengthened by general overweight/obesity, abdominal obesity, hypertriglyceridemia and non-smoking status. In conclusion, parameters related to lipid alterations are associated with oxidative stress in LC patients. The largest contribution from lipid parameters was revealed for T-C:HDL-C ratio, HDL-C and Apo-B:Apo-A1 ratio, while the largest contribution from redox status was revealed for OSI and VE. Overweight, obesity, hypertriglyceridemia and non-smoking status intensified these relationships.

Endogenously generated DNA nucleobase modifications source, and significance as possible biomarkers of malignant transformation risk, and role in anticancer therapy

The DNA of all living cells undergoes continuous structural and chemical alteration, which may be derived from exogenous sources, or endogenous, metabolic pathways, such as cellular respiration, replication and DNA demethylation. It has been estimated that approximately 70,000 DNA lesions may be generated per day in a single cell, and this has been linked to a wide variety of diseases, including cancer. However, it is puzzling why potentially mutagenic DNA modifications, occurring at a similar level in different organs/tissue, may lead to organ/tissue specific cancers, or indeed non-malignant disease - what is the basis for this differential response? We suggest that it is perhaps the precise location of damage, within the genome, that is a key factor. Finally, we draw attention to the requirement for reliable methods for identification and quantification of DNA adducts/modifications, and stress the need for these assays to be fully validated. Once these prerequisites are satisfied, measurement of DNA modifications may be helpful as a clinical parameter for treatment monitoring, risk group identification and development of prevention strategies.

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.

Serum Vitamin A and Inflammatory Markers in Individuals with and without Chronic Obstructive Pulmonary Disease

BACKGROUND

Vitamin A is essential for the preservation and integrity of the lung epithelium and exerts anti-inflammatory effects.

OBJECTIVE

Evaluating vitamin A in the serum and sputum and testing its correlation with inflammatory markers in individuals with or without COPD. Methods. We evaluated dietary intake, serum and sputum vitamin A, tumor necrosis factor alpha, interleukin- (IL-) 6, IL-8, and C-reactive protein in 50 COPD patients (age = 64.0 ± 8.8 y; FEV1 (forced expiratory volume in the first second) (%) = 49.8 ± 16.8) and 50 controls (age = 48.5 ± 7.4 y; FEV1 (%) = 110.0 ± 15.7).

RESULTS

COPD exhibited lower serum vitamin A (1.8 (1.2-2.1) versus 2.1 (1.8-2.4) μmol/L, P < 0.001) and lower vitamin A intake (636.9 (339.6-1349.6) versus 918.0 (592.1-1654.6) RAE, P = 0.05) when compared with controls. Sputum concentration of vitamin A was not different between groups. Sputum vitamin A and neutrophils were negatively correlated (R (2) = -0.26; P = 0.03). Smoking (0.197, P = 0.042) exhibited positive association with serum vitamin A. COPD was associated with lower serum concentrations of vitamin A without relationship with the systemic inflammation.

CONCLUSIONS

Serum concentration of vitamin A is negatively associated with the presence of COPD and positively associated with smoking status. Sputum retinol is quantifiable and is negatively influenced by neutrophils. Although COPD patients exhibited increased inflammation it was not associated with serum retinol.

The APE1 Asp/Asp genotype and the combination of APE1 Asp/Asp and hOGG1-Cys variants are associated with increased p53 mutation in non-small cell lung cancer

Background

The hOGG1 Ser326Cys polymorphism is associated with lung cancer risk, but there are limited data regarding an association between the APE1 Asp148Glu polymorphism and lung cancer. Biological evidence shows that the hOGG1-Cys allele results in less DNA repair activity; however, this is not associated with p53 mutation in lung cancer. Therefore, we investigated whether an interaction between hOGG1 and APE1 is associated with the frequency of p53 mutation in lung cancer.

Methods

We studied 217 Taiwanese adults with primary lung cancer. DNA polymorphisms of hOGG1 and APE1 were determined by polymerase chain reaction (PCR)-based restriction fragment length polymorphism. Mutations in p53 exons 5–8 were detected by direct sequencing. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% CIs for the risk of p53 mutation associated with polymorphisms of hOGG1 and APE1 in lung cancer.

Results

As expected, no association between hOGG1 polymorphism and p53 mutation was observed in this population. However, a higher risk of p53 mutation was found in participants with the APE1 Asp/Asp genotype than in those with the APE1-Glu allele (OR, 2.15; 95% CI, 1.19–3.87; P = 0.011). The risk of p53 mutation was also higher in participants with APE1 Asp/Asp plus hOGG1-Cys than in those with APE1-Glu plus hOGG1 Ser/Ser (OR, 3.72; 95% CI, 1.33–10.40; P = 0.012).

Conclusions

These results suggest that the APE1 Asp/Asp genotype and the combination of the APE1 Asp/Asp and hOGG1-Cys variants are associated with increased risk of p53 mutation in non–small cell lung cancer.

Assessment of 8-oxo-7, 8-dihydro-2'-deoxyguanosine and malondialdehyde levels as oxidative stress markers and antioxidant status in non-small cell lung cancer

OBJECTIVE

The present investigation was taken up to evaluate the 8-oxo-7,8-dihydro-2'-deoxyguanosine and malondialdehyde as markers of oxidative stress, the levels of antioxidants and the correlations between these oxidative stress markers and antioxidants in lung cancer patients.

METHODS

The study included 222 patients (158 men and 64 women, age ranging from 32 to 85 years) and 207 control subjects (153 men and 54 women, aged 30-80 years) for the analysis of urinary excretion of 8-oxodG using an ELISA assay, plasma malondialdehyde using spectrophotometer and red cell Cu-Zn SOD and GPx activities by kit methods.

RESULTS

The levels of 8-oxodG and malondialdehyde were significantly higher (p < 0.001) and red cell superoxide dismutase and glutathione peroxidase activities (p < 0.001) were significantly lower in lung cancer patients than in controls. There was a significantly positive correlation between 8-oxodG and malondialdehyde (r=0.912, p < 0.001) and a negative correlation between 8-oxodG and antioxidants.

CONCLUSIONS

Our results demonstrate that an increased rate of oxidative stress might play a role in the pathogenesis of lung cancer as evidenced by a failure in the oxidant/antioxidant balance in favour of lipid peroxidation and DNA damage.

Bronchoalveolar lavage fluid alteration in antioxidant and inflammatory status in lung cancer patients

BACKGROUND

Increased oxidative and inflammatory markers have been reported in lung cancer patients, but relatively few studies have investigated the presence of antioxidants both in the local lung environment and in the systemic circulation. Furthermore, it is hypothesized that the immune system activation in vivo is regulated by the redox environment.

OBJECTIVES

To investigate local and systemically circulating antioxidant and inflammatory mediators in lung cancer patients and potential correlations between them.

METHODS

Forty two male patients (mean age 65±8years) with primary lung cancer were studied. Sixteen age and smoking history matched male subjects without any evidence of malignancy served as controls. Total antioxidant status (TAS) and glutathione (GSH), as well as interleukin-1a (IL-1a), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) were measured in bronchoalveolar lavage fluid (BALF) and serum samples.

RESULTS

A statistically significant increase of TAS and GSH in BALF was observed in lung cancer patients compared to healthy subjects (0.27±0.24 vs. 0.12±0.02mmol/L, p=0.02 and 7.56±4.29 vs. 4.62±2.23μmol/L, p=0.01 respectively). Statistically significant correlations in cancer patients were observed in BALF between TAS and a. IL-1α (r=0.87, p<0.001), b. IL-6 (r=0.52, p=0.001) and c. TNF-α (r=0.67, p<0.001).

CONCLUSIONS

Alteration in antioxidant and inflammatory mediator status was found in lung cancer patients both in serum and in BALF compared to healthy subjects matched for smoking history. Moreover, a positive correlation was observed between antioxidants and pro-inflammatory cytokines, but only locally and not systematically.

Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis

BACKGROUND

Despite reported antiproliferative activity of vitamin A and its common use for cancer, there is no comprehensive synthesis of its safety and efficacy in lung cancers. To address this issue we conducted a systematic review of the safety and efficacy of vitamin A for the treatment and prevention of lung cancers.

METHODS AND FINDINGS

Two independent reviewers searched six electronic databases from inception to July 2009 for clinical, observational, and preclinical evidence pertaining to the safety and efficacy of vitamin A and related retinoids for lung cancers. 248 studies were included for full review and analysis. Five RCTs assessed treatment of lung cancers, three assessed primary prevention, and three looked at secondary prevention of lung cancers. Five surrogate studies, 26 phase I/II, 32 observational, and 67 preclinical studies were also included. 107 studies were included for interactions between vitamin A and chemo- or radiation-therapy. Although some studies demonstrated benefits, there was insufficient evidence overall to support the use of vitamin A or related retinoids for the treatment or prevention of lung cancers. Retinyl palmitate combined with beta carotene increased risk of lung cancer in smokers in the large CARET trial. Pooling of three studies pertaining to treatment and three studies on secondary prevention revealed no significant effects on response rate, second primary tumor, recurrence, 5-year survival, and mortality. There was a small improvement in event free survival associated with vitamin A compared to controls, RR 1.24 (95% CI 1.13-1.35). The synthetic rexinoid bexarotene increased survival significantly among a subset of patients in two RCTs (p<0.014, <0.087).

CONCLUSIONS

There is a lack of evidence to support the use of naturally occurring retinoids for the treatment and prevention of lung cancers. The rexinoid bexarotene may hold promise for use among a subset of patients, and deserves further study.

Triphlorethol-a improves the non-homologous end joining and base-excision repair capacity impaired by formaldehyde

Formaldehyde (HCHO) generates reactive oxygen species (ROS) that induce DNA base modifications and DNA strand breaks and contributes to mutagenesis and other pathological processes. DNA non-homologous end-joining (NHEJ), a major mechanism for repairing DNA double-stranded breaks (DSB) in mammalian cells, involves the formation of a Ku protein heterodimer and recruitment of a DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to the site of DNA damage. HCHO treatment induced DSB and decreased the protein expressions of Ku 70 and phosphorylated DNA-PKcs. Triphlorethol-A reduced DNA strand breaks and restored the expression of NHEJ-related proteins. In response to oxidative DNA base damage, 8-oxoguanine DNA glycosylase 1 (OGG1) plays a vital role in repair of 8-hydroxy-2'-deoxyguanosine (8-OhdG) via the base-excision repair (BER) process. In this study, HCHO significantly increased 8-OhdG levels, whereas triphlorethol-A lowered 8-OhdG levels. Suppression of 8-OhdG formation by triphlorethol-A was related to enhanced OGG1 protein expression. Triphlorethol-A also enhanced the expression of phosphorylated Akt (the active form of Akt), a regulator of OGG1, which was found to be decreased by HCHO treatment. The phosphoinositol 3-kinase (PI3K)-specific inhibitor LY294002 abolished the cytoprotective effects induced by triphlorethol-A, suggesting that OGG1 restoration by triphlorethol-A is involved in the PI3K/Akt pathway. These results suggest that triphlorethol-A may protect cells against HCHO-induced DNA damage via enhancement of NHEJ and BER capacity.

Induction of NEIL1 and NEIL2 DNA glycosylases in aniline-induced splenic toxicity

The mechanisms by which aniline exposure elicits splenotoxic response, especially the tumorigenic response, are not well-understood. Earlier, we have shown that aniline-induced oxidative stress is associated with increased oxidative DNA damage in rat spleen. The base excision repair (BER) pathway is the major mechanism for the repair of oxidative DNA base lesions, and we have shown an up-regulation of 8-oxoguanine glycosylase 1 (OGG1), a specific DNA glycosylase involved in the removal of 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts, following aniline exposure. Nei-like DNA glycosylases (NEIL1/2) belong to a family of BER proteins that are distinct from other DNA glycosylases, including OGG1. However, contribution of NEIL1/2 in the repair of aniline-induced oxidative DNA damage in the spleen is not known. This study was, therefore, focused on evaluating if NEILs also contribute to the repair of oxidative DNA lesions in the spleen following aniline exposure. To achieve that, male SD rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. The BER activity of NEIL1/2 was assayed using a bubble structure substrate containing 5-OHU (preferred substrates for NEIL1 and NEIL2) and by quantitating the cleavage products. Aniline treatment led to a 1.25-fold increase in the NEIL1/2-associated BER activity in the nuclear extracts of spleen compared to the controls. Real-time PCR analysis for NEIL1 and NEIL2 mRNA expression in the spleen revealed 2.7- and 3.9-fold increases, respectively, in aniline-treated rats compared to controls. Likewise, Western blot analysis showed that protein expression of NEIL1 and NEIL2 in the nuclear extract of spleens from aniline-treated rats was 2.0- and 3.8-fold higher than controls, respectively. Aniline treatment also led to stronger immunoreactivity for NEIL1 and NEIL2 in the spleens, confined to the red pulp areas. These studies, thus, show that aniline-induced oxidative stress is associated with an induction of NEIL1/2. The increased NIEL-mediated BER activity is another indication of aniline-induced oxidative damage in the spleen and could constitute another important mechanism of removal of oxidative DNA lesions, especially in transcribed DNA following aniline insult.

8-oxo-7,8-dihydro-2'-deoxyguanosine as a biomarker of oxidative damage in oesophageal cancer patients: lack of association with antioxidant vitamins and polymorphism of hOGG1 and GST

Background

The present report was designed to investigate the origins of elevated oxidative stress measured in cancer patients in our previous work related to a case-control study (17 cases, 43 controls) on oesophageal cancers. The aim was to characterize the relationship between the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), antioxidant vitamins and genetic susceptibility.

Methods

8-oxodG was analysed in peripheral blood mononuclear cells (PBMCs) by High Performance Liquid Chromatography with Electrochemical Detection (HPLC-ED). Analysis of gene polymorphisms in GSTM1 and GSTT1 was performed by multiplex PCR and in GSTP1 and hOGG1 by a PCR-RFLP method. Reversed-phase HPLC with UV detection at 294 nm was used to measure vitamins A and E in serum from the same blood samples.

Results

We observed that in our combined population (cases and control, n = 60), there was no statistically significant correlation between the levels of 8-oxodG and (i) the serum concentration of antioxidant vitamins, vitamin A (P = 0.290) or vitamin E (P = 0.813), or (ii) the incidence of the Ser326Cys polymorphic variant (P = 0.637) of the hOGG1 gene. Also, the levels of 8-oxodG were not significantly associated with polymorphisms in metabolite-detoxifying genes, such as GSTs, except for the positive correlation with Val/Val GST P1 allele (P < 0.0001).

Conclusions

The weakness of our cohort size notwithstanding, vitamins levels in serum and genetic polymorphisms in the hOGG1 or GST genes do not appear to be important modulators of 8-oxodG levels.

Elevated level of 8-oxo-7,8-dihydro-2'-deoxyguanosine in leukocytes of BRCA1 mutation carriers compared to healthy controls

Carriers of BRCA1 mutation face highly increased risk of breast and ovarian cancer and some studies with cell culture suggest that the encoded protein may be involved in oxidatively damaged DNA repair. However, no studies concerning a possible link between oxidatively damaged DNA and BRCA1 deficiency have been conducted with the mutations carriers. Therefore, to assess an involvement of BRCA in oxidative damage to DNA in the present study a broad spectrum of parameters reflecting oxidative stress/DNA damage were analyzed in 3 subject groups; (i) carriers of BRCA1 mutations without symptoms of the disease; (ii) patients with breast or ovarian cancer with the mutations and (iii) the group of healthy subjects recruited from among close relatives of the group of carriers without symptoms of the disease. We found that the endogenous levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in leukocytes DNA and excretion rates of urinary 8-oxodG were significantly higher in the cancer patients than in the healthy carriers. Similarly, to the cancer patient group, 8-oxodG level in leukocytes DNA is significantly higher in the carriers group in comparison with control group. That the control group comprised close relatives of the carriers gives further credit to our finding. Since we did not observe substantial differences in the analyzed markers of oxidative stress between the controls and the carriers, the observed increase in the level may be a result of a deficiency in the repair of 8-oxodG.

Fluorescent detection of lipid peroxidation derived protein adducts upon in-vitro cigarette smoke exposure

Oxidative stress in biological systems can result in radical-induced lipid peroxidation (LPO), which can lead to the production of secondary reactive by-products such as 4-hydroxy-2-nonenal (HNE), malondialdehyde (MDA), acrolein, and acetaldehyde. These deleterious compounds are known to react with and concomitantly modify nucleophilic amino acid residues on proteins. Oxidative stress induced by cigarette smoke (CS) has been put forth as a major mechanism for tobacco-induced pathologies. At present, there are few reliable biomarkers for measuring the extent of oxidatively-induced damage resulting from CS exposure in vivo. This study has utilized a previously reported CS exposure system to expose cultured cells in-vitro to whole CS and determine the extent of LPO resulting from CS exposure by quantifying the increase in HNE within the exposure media versus controls via gas chromatography mass spectrometry. Additionally, we obtained protein enriched cell lysate post-CS exposures and measured the fluorescent signal obtained via direct injection fluorescent analysis at 375 nm ex./415 nm em. This study determined that the fluorescent signal intensity was directly proportional to the quantity increase of HNE in CS exposed media. It further tested this correlation by performing HNE titration addition experiments to cultured cells and Western blot analysis on proteins obtained from cell lysates. Finally, the fluorescent signal increase from authentic BSA solutions incubated with increasing concentrations of HNE was measured. It is proposed that the fluorescent signal observed from the protein lysate of CS exposed cultured cells corresponds to the extent of biological damage resulting from secondary reactive by-products formed from LPO induced via CS exposure and represented by HNE. The fluorescent signals increased in intensity upon increasing CS dose up to 20 min and remained elevated over 24 h after cessation of CS exposure.

Tocopherol isomer pattern in serum and stool of human following consumption of black currant seed press residue administered in whole grain bread

BACKGROUND & AIMS

Serum gamma-tocopherol is thought to be associated with human health. The dietary influence of tocopherol and fibre-rich black currant seed press residue on serum and stool tocopherol concentration was investigated in a controlled human intervention study.

METHODS

Thirty-six women consumed bread enriched with black currant press residue (4 weeks). The resultant faecal and serum tocopherol concentrations were compared with those after a period consuming control bread without press residue and a normal baseline diet. Fibre intake and excretion, antioxidant capacity (TEAC), and vitamin C concentrations in serum and urine were also determined. Samples were obtained with a 5-day standardised diet at the end of each period.

RESULTS

The press residue bread lead to significantly increased beta-, gamma-, delta- and total tocopherol intake, serum alpha-, beta-, gamma- and total tocopherol concentration (with and without lipid adjustment), fibre intake and urinary vitamin C concentration compared to control bread (P<0.05). Faecal excretion of total tocopherols and fibre increased compared to baseline (P<0.05).

CONCLUSIONS

Fibre intake and excretion influence total tocopherol concentration in lipid-adjusted serum and in stool. The outstandingly high increase of serum gamma-tocopherol concentration through seed press residue consumption could be due to a presumed interruption of the enzymatic tocopherol degradation mechanism by bread constituents.

Biomarkers of exposure to tobacco smoke and environmental pollutants in mothers and their transplacental transfer to the foetus. Part II. Oxidative damage

Oxidative damage to macromolecules may have numerous negative health consequences. We measured oxidative damage to DNA, proteins and lipids in 80 newborns and 79 mothers, analyzed the effect of mother's tobacco smoke exposure on oxidative stress, and assessed correlations between oxidative stress markers and bulky and PAH (polycyclic aromatic hydrocarbons)-specific DNA adducts. Mean levels (+/-S.D.) of 8-oxodeoxyguanosine (8-oxodG) per 10(5) dG in the placenta were 2.85+/-0.78; we did not see a difference between 8-oxodG levels in newborns born to mothers exposed and unexposed to tobacco smoke. Protein carbonyl levels, a marker of protein oxidation, were comparable in the umbilical cord and in maternal venous blood plasma (17.4+/-3.2 and 17.6+/-4.2nmol/ml plasma in newborns and mothers, respectively, p=0.66). Lipid peroxidation measured as levels of 15-F(2t)-isoprostane (15-F(2t)-IsoP) in plasma was significantly higher in newborns than in mothers (362+/-129 and 252+/-130pg/ml in newborns and mothers, respectively, p<0.001). We did not find any effect of tobacco smoke exposure on either biomarker in any group. Levels of both protein carbonyls and 15-F(2t)-IsoP in cord blood significantly correlated with those in maternal plasma (p<0.001). 8-oxodG levels positively correlated with plasma carbonyls in cord plasma, as well as with cotinine levels (marker of tobacco smoke exposure) in maternal plasma. 8-oxodG levels also correlated with bulky DNA adducts in lymphocyte DNA of newborns and mothers and with PAH-DNA adducts in the placenta. Our results showed higher lipid peroxidation in newborns than in mothers, close correlation of analyzed oxidative stress markers between newborns and mothers, and a relationship between oxidative stress and induction of DNA adducts.

Impact of radiotherapy and chemotherapy on biomarkers of oxidative DNA damage in lung cancer patients

OBJECTIVES

To assess oxidative damage to DNA during lung cancer (LC) treatments.

DESIGN AND METHODS

Urinary levels of 8-oxoguanine (8-oxoGua) and levels of 8-oxo-2'-deoxyguanosine (8-oxodG) from urine and whole blood were determined in 36 non-cancer controls and 65 LC patients before any treatments. Samples were also obtained of LC patients during and after radiotherapy (RT, n=33) and chemotherapy (CT, n=16).

RESULTS

Stage IV LC patients had higher urinary 8-oxoGua and 8-oxodG levels than patients with stage I-III disease (p=0.044 and p=0.034, respectively). Urinary 8-oxodG levels increased during the first week of RT (p<0.001). Nuclear 8-oxodG increased during RT and 3 months after start of RT. Nuclear 8-oxodG levels also rose between the first two CT cycles (p=0.043), and urinary 8-oxodG levels during the sixth CT cycle (p=0.009).

CONCLUSIONS

Urinary DNA damage biomarker levels may be associated with LC stage. Both RT and CT increase the parameters of DNA oxidation.

Antioxidant intervention of smoking-induced lung tumor in mice by vitamin E and quercetin

Background

Epidemiological and in vitro studies suggest that antioxidants such as quercetin and vitamin E (VE) can prevent lung tumor caused by smoking; however, there is limited evidence from animal studies.

Methods

In the present study, Swiss mouse was used to examine the potential of quercetin and VE for prevention lung tumor induced by smoking.

Results

Our results suggest that the incidence of lung tumor and tumor multiplicity were 43.5% and 1.00 ± 0.29 in smoking group; Quercetin has limited effects on lung tumor prevention in this in vivo model, as measured by assays for free radical scavenging, reduction of smoke-induced DNA damage and inhibition of apoptosis. On the other hand, vitamin E drastically decreased the incidence of lung tumor and tumor multiplicity which were 17.0% and 0.32 ± 0.16, respectively (p < 0.05); and demonstrated prominent antioxidant effects, reduction of DNA damage and decreased cell apoptosis (p < 0.05). Combined treatment with quercetin and VE in this animal model did not demonstrate any effect greater than that due to vitamin E alone. In addition, gender differences in the occurrence of smoke induced-lung tumor and antioxidant intervention were also observed.

Conclusion

We conclude that VE might prevent lung tumor induced by smoking in Swiss mice.

Nuclear oxidative damage correlates with poor survival in colorectal cancer

Oxidative DNA damage results from DNA adducts such as 8-oxo-7, 8 dihydro-2′-deoxyguanosine (8-oxo-dG), which is a pro-mutagenic lesion. No known association between 8-oxo-dG, disease progression and survival exists in colorectal cancer (CRC). We examined levels of 8-oxo-dG in sporadic CRC to determine its relationship with pathological stage and outcome. A total of 143 CRC patients and 105 non-cancer patients were studied. Nuclear and cytoplasmic 8-oxo-dG was assessed using immunohistochemistry. Double immunofluorescence using 8-oxo-dG and manganese superoxide dismutase (MnSOD) antibodies localised cytoplasmic 8-oxo-dG. Apoptosis was detected using TUNEL. Nuclear staining levels were similar in tumour tissue and matched normal mucosa in both epithelial (P=0.22) and stromal (P=0.85) cells. Epithelial cytoplasmic staining was greater in tumour tissue (P<0.001). Double immunofluorescence localised cytoplasmic 8-oxo-dG to mitochondria. Epithelial and stromal nuclear 8-oxo-dG decreased with local disease spread, but highest levels were found in distant disease (P<0.01). Survival was related to epithelial nuclear and stromal staining in normal mucosa (P<0.001) and tumour (P<0.01) but was unrelated to cytoplasmic staining. Normal control cells in tissue from cancer patients with high levels of 8-oxo-dG failed to undergo cell death. 8-oxo-dG may be an important biomarker of disease risk, progression and survival for CRC patients.

DNA oxidation: investigating its key role in environmental mutagenesis with the comet assay

DNA oxidation, which can have potentially serious mutagenic consequences, commonly accompanies exposure to environmental mutagens. Oxidised bases can be measured chromatographically, but spurious oxidation during sample preparation leads to serious over-estimation of low levels of damage. A more reliable approach is to employ endonucleases specific for oxidised bases, to introduce breaks in cellular DNA that are then most commonly measured using the comet assay (alkaline single cell gel electrophoresis). The two enzymes in general use are formamidopyrimidine DNA glycosylase, which detects primarily 8-oxo-7,8-dihydroguanine (8-oxoGua), and endonuclease III which recognises oxidised pyrimidines. We give a brief account of the recommended experimental procedures, and then describe applications in various areas of environmental research. Cultured cell lines or white blood cells have been exposed to a range of environmental mutagens, including natural products, industrial chemicals, radiation and nanoparticles. In vivo exposure of animals and humans to pollutants is more challenging but can give particularly valuable information in relation to real life exposure. Possibly the most useful application is in biomonitoring of human population groups suffering actual exposure to environmental or occupational mutagens. Finally, the potential use of this technique to monitor effects of contaminants in the natural environment has yet to be fully exploited.

Oxidative DNA damage and its repair in rat spleen following subchronic exposure to aniline

The mechanisms by which aniline exposure elicits splenotoxic response, especially the tumorigenic response, are not well-understood. Splenotoxicity of aniline is associated with iron overload and generation of reactive oxygen species (ROS) which can cause oxidative damage to DNA, proteins and lipids (oxidative stress). 8-Hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most abundant oxidative DNA lesions resulting from ROS, and 8-oxoguanine glycosylase 1 (OGG1), a specific DNA glycosylase/lyase enzyme, plays a key role in the removal of 8-OHdG adducts. This study focused on examining DNA damage (8-OHdG) and repair (OGG1) in the spleen in an experimental condition preceding a tumorigenic response. To achieve that, male Sprague-Dawley rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. Aniline treatment led to a significant increase in splenic oxidative DNA damage, manifested as a 2.8-fold increase in 8-OHdG levels. DNA repair activity, measured as OGG1 base excision repair (BER) activity, increased by approximately 1.3 fold in the nuclear protein extracts (NE) and approximately 1.2 fold in the mitochondrial protein extracts (ME) of spleens from aniline-treated rats as compared to the controls. Real-time PCR analysis for OGG1 mRNA expression in the spleen revealed a 2-fold increase in expression in aniline-treated rats than the controls. Likewise, OGG1 protein expression in the NEs of spleens from aniline-treated rats was approximately 1.5 fold higher, whereas in the MEs it was approximately 1.3 fold higher than the controls. Aniline treatment also led to stronger immunostaining for both 8-OHdG and OGG1 in the spleens, confined to the red pulp areas. It is thus evident from our studies that aniline-induced oxidative stress is associated with increased oxidative DNA damage. The BER pathway was also activated, but not enough to prevent the accumulation of oxidative DNA damage (8-OHdG). Accumulation of mutagenic oxidative DNA lesions in the spleen following exposure to aniline could play a critical role in the tumorigenic process.

Cigarette smoke induces endoplasmic reticulum stress and the unfolded protein response in normal and malignant human lung cells

Background

Although lung cancer is among the few malignancies for which we know the primary etiological agent (i.e., cigarette smoke), a precise understanding of the temporal sequence of events that drive tumor progression remains elusive. In addition to finding that cigarette smoke (CS) impacts the functioning of key pathways with significant roles in redox homeostasis, xenobiotic detoxification, cell cycle control, and endoplasmic reticulum (ER) functioning, our data highlighted a defensive role for the unfolded protein response (UPR) program. The UPR promotes cell survival by reducing the accumulation of aberrantly folded proteins through translation arrest, production of chaperone proteins, and increased degradation. Importance of the UPR in maintaining tissue health is evidenced by the fact that a chronic increase in defective protein structures plays a pathogenic role in diabetes, cardiovascular disease, Alzheimer's and Parkinson's syndromes, and cancer.

Methods

Gene and protein expression changes in CS exposed human cell cultures were monitored by high-density microarrays and Western blot analysis. Tissue arrays containing samples from 110 lung cancers were probed with antibodies to proteins of interest using immunohistochemistry.

Results

We show that: 1) CS induces ER stress and activates components of the UPR; 2) reactive species in CS that promote oxidative stress are primarily responsible for UPR activation; 3) CS exposure results in increased expression of several genes with significant roles in attenuating oxidative stress; and 4) several major UPR regulators are increased either in expression (i.e., BiP and eIF2α) or phosphorylation (i.e., phospho-eIF2α) in a majority of human lung cancers.

Conclusion

These data indicate that chronic ER stress and recruitment of one or more UPR effector arms upon exposure to CS may play a pivotal role in the etiology or progression of lung cancers, and that phospho-eIF2α and BiP may have diagnostic and/or therapeutic potential. Furthermore, we speculate that upregulation of UPR regulators (in particular BiP) may provide a pro-survival advantage by increasing resistance to cytotoxic stresses such as hypoxia and chemotherapeutic drugs, and that UPR induction is a potential mechanism that could be attenuated or reversed resulting in a more efficacious treatment strategy for lung cancer.

Increased levels of 8-hydroxydeoxyguanosine and its relationship with lipid peroxidation and antioxidant vitamins in lung cancer

BACKGROUND

Reactive oxygen species produced either endogenously or exogenously can attack lipids, proteins and DNA in human cells and cause potentially deleterious consequences. In recent years, their role in the pathogenesis of lung cancer and the preventive effect of antioxidants have been studied extensively. In this study, our aim was to investigate the levels of 8-hydroxy-2'-deoxyguanosine (8OHdG) and malondialdehyde as a marker for the effects of reactive oxygen species on DNA and lipids, the levels of antioxidant vitamins and the correlations between these oxidative stress markers and antioxidants in lung cancer.

METHODS

Serum malondialdehyde, beta-carotene, retinol, and vitamins C and E were measured by high-performance liquid chromatography methods in fasting blood samples and 8OHdG was measured by gas chromatography-mass spectrometry in 24-h urine samples of patients with lung cancer (n=39) and healthy controls (n=31).

RESULTS

The levels of 8OHdG and malondialdehyde were significantly higher (p<0.05 and p<0.005, respectively) and beta-carotene, retinol, and vitamins C and E (p<0.0001, p<0.0001, p<0.0001, and p<0.05, respectively) were significantly lower in patients than in controls. There was a significantly positive correlation between 8OHdG and malondialdehyde (r=0.463, p=0.01) and a negative correlation between the levels of 8OHdG and retinol (r=-0.419, p=0.021) in the patient group.

CONCLUSIONS

Our results demonstrate that the oxidant/antioxidant balance was spoiled in favor of lipid peroxidation and DNA damage in lung cancer patients. Significant increases in the levels of malondialdehyde and 8OHdG and decreases in the levels of antioxidants suggest the possible involvement of oxidative stress in lung cancer.

Effect of Supplemented and Topically Applied Antioxidant Substances on Human Tissue

Systemic and topical application of antioxidant substances for the medical treatment and prophylaxis of many diseases as well as additional protection of the skin against the destructive action of free radicals and other reactive species has become very popular during the past years. Stimulated by the positive results of a fruit and vegetable diet in supporting medical treatment and in cosmetics, artificial and extracted antioxidant substances have been broadly applied. Surprisingly, not only positive but also strong negative results have been obtained by different authors. According to study reports artificial and extracted antioxidant substances support different kinds of medical therapies, if they are applied in mixtures of different compounds at low concentration levels. In the case of the application of high concentration of some single compounds, side effects were often observed. Regarding skin treatment by systemically applied antioxidant substances for cosmetic purposes, positive cosmetic effects as well as no effects, but almost no side effects, apart from a number of allergic reactions, were reported. One reason for this seems to be the lower concentration of systemically applied antioxidant substances in comparison with a medical application. Topical application of antioxidant substances is closely related to cosmetic treatment for skin protection and anti-aging. Positive results were also obtained in this case. The present review is an attempt to classify and summarize the published literature concerning the efficiency of action of systemic and topical applications of antioxidant substances, such as carotenoids and vitamins, on human organism and especially on the skin. The available literature on this topic is very extensive and the results are often contradictory. Nevertheless, there are some clear tendencies concerning systemic and topical application of antioxidant substances in medicine and cosmetics, and we summarize them in the present paper.

Serum retinoic acid, retinol and retinyl palmitate levels in patients with lung cancer

OBJECTIVES

Epidemiological studies have shown an inverse relationship between dietary vitamin A intake and the risk of developing lung cancer. The aim of this study was to investigate the vitamin A status in patients with lung cancer, by determining the serum levels of retinoic acid, retinol and retinyl palmitate.

METHODS

In total, 36 patients with lung cancer and 27 controls were assessed. Of the patients 14 had squamous cell carcinoma, 3 adenocarcinoma, 15 non-small cell lung cancer and 4 small cell lung cancer. Serum retinoic acid, retinol and retinyl palmitate levels were determined with HPLC and UV detection, after liquid extraction.

RESULTS

Serum retinol levels did not differ between patients (733.5 +/- 326.4 ng/mL) and controls (734.5 +/- 337.1 ng/mL). The retinyl palmitate concentration tended to be lower in patients (14.3 +/- 9.7 ng/mL) than in controls (16.7 +/- 13.7 ng/mL). The serum retinoic acid levels were significantly lower in patients (1.9 +/- 0.6 ng/mL) than in controls (2.5 +/- 1.1 ng/mL, P < 0.05). A positive correlation was observed between the retinol and retinoic acid levels and retinyl palmitate and retinoic acid levels.

CONCLUSIONS

The lower levels of retinoic acid in patients with lung cancer suggest there may be a deficiency or impairment in retinol metabolism in these patients. Further studies with larger numbers of patients are needed to evaluate the possible relationship between serum retinoid levels and lung cancer.

Severe oxidatively damaged DNA after cisplatin treatment of cancer patients

There is growing evidence suggesting that cytotoxic activity of cisplatin is closely associated with increased generation of reactive oxygen species (ROS). Therefore, this study was undertaken to examine oxidative DNA damage, which arises as a result of chemotherapy with cisplatin. Using HPLC prepurification/isotope dilution GC/MS methodology, we examined the amount of 8-oxoGua and 8-oxodG excreted into urine in cancer patients (n = 66) who received chemotherapy with cisplatin. One day after the infusion of the drug, significant increase in the amount of 8-oxoGua and 8-oxodG in urine of the patients was observed, when compared to the initial value (78%, p < 0.0001 and 22%, p = 0.0051). In the "nadir days" (when the most distinct cell death based on hematological cell counts can be observed), the level of modified base and nucleoside decreased in comparison with the aforementioned time point. These results, for the first time, indicate that oxidatively damaged DNA may be, at least in part, responsible for cisplatin induced cytotoxicity. Our results also demonstrate that cell death does not contribute to urinary 8-oxoGua and 8-oxodG in humans.

Oxidative DNA damage and human cancer: need for cohort studies

Research of the role of oxidative DNA damage is well established in experimental carcinogenesis. A large number of human studies on biomarkers of oxidative DNA damage, in particular related to guanine oxidation, have been published. The level of oxidative DNA damage and repair activity can be quite different between tumor and normal tissues; case-control studies have shown increased levels of oxidative DNA damage and decreased repair capacity in leukocytes from cases. Similarly, the urinary biomarkers of oxidative DNA damage may be elevated in patients with cancer. However, such studies are likely to be associated with reverse causality. Case-control studies of genetic polymorphisms in DNA repair enzymes suggest that the common variant Ser326Cys in OGG1 may be a risk factor for lung cancer, whereas a rare variant in OGG1 and germ line mutations in the corresponding mismatch repair gene MYH are risk factors for hereditary colon cancer. Cohort studies are required to provide evidence that a high level of oxidative DNA damage implies a high risk of cancer. However, this represents a real challenge considering the large number of subjects and long followup time required with likely spurious oxidation of DNA during collection, assay and/or storage of samples.

Abasic sites and survival in resected patients with non-small cell lung cancer

Apurinic/apyrimidinic (AP or abasic) sites are common DNA lesions that arise from spontaneous depurination or by base excision repair (BER) of modified bases. Accumulation of impaired AP sites could lead to increased genomic instability that in turn could lead to a more malignant phenotypic behavior of tumors. We, therefore, evaluated the effects of AP sites on survival in resected non-small cell lung cancer (NSCLC) patients. Resected tumor specimens from 99 patients with NSCLC who underwent surgical resection were collected. The enzyme-linked immunosorbent assay was applied to measure the levels of AP sites in tumor DNA. The median number of AP sites per 10(5) nucleotides was 12.4 for all the study subjects. Patients with low levels of AP site had significantly longer survival time compared with ones with medium or high levels of AP site (log-rank test: P=0.015). In Cox regression analysis, patients with medium or high levels of AP sites had over twofold increased hazard of death. In addition, we found a statistically significant correlation between levels of AP sites and age (rho=0.560, P<0.001). The results of this study demonstrated that levels of AP sites could predict survival in resected NSCLC patients. We postulate that an intact BER mechanism may reduce the accumulation of oxidative DNA damage that are thought to contribute to the tumor's malignant potential and therefore the risk of death.

Long-term Cryoconservation and Stability of Vitamin C in Serum Samples of the European Prospective Investigation into Cancer and Nutrition

Plasma vitamin C level may be associated with risk of some chronic diseases. The rapid degradability of vitamin C in biological samples necessitates its stabilization with metaphosphoric acid or similar agents. However, in most cohort studies, prospectively collected biological samples are not treated with stabilizing agents before long-term frozen storage and it is not known whether vitamin C can be properly measured in such samples. The objective of this study was to determine the degree of vitamin C degradation in plasma samples stored without stabilization for 7 to 11 years at -196 degrees C. Spearman's correlation coefficients indicate a moderate correlation between baseline and final plasma vitamin C levels in both men (r = 0.57, P < 0.0001) and women (r = 0.52, P < 0.0001). Samples were also categorized based on low or high baseline levels of plasma vitamin C, with the latter category showing the highest rate of loss per year of frozen storage in men (1.96 micromol/L, P value for difference <0.0001; percent loss 24.6%) and women (2.35 micromol/L, P value for difference <0.0001; percent loss 24.2%), as determined by multiple regression analysis adjusted for smoking status, age, and body mass index. In men, both baseline and final plasma vitamin C values were lower in smokers than never smokers, but for both men and women the rate of vitamin C loss during storage was not significantly different between smokers and never smokers. The results of this study show that vitamin C can be measured with reasonable reliability in plasma samples frozen for long periods of time without addition of any stabilizing agents.