Isoprostanes quickly normalize after quitting cigarette smoking in healthy adults

Biological and Functional Changes in Healthy Adult Smokers Who Are Continuously Abstinent From Smoking for One Year: Protocol for a Prospective, Observational, Multicenter Cohort Study

Background

The harm of smoking results mainly from long-term exposure to harmful and potentially harmful constituents (HPHCs) generated by tobacco combustion. Smoking cessation (SC) engenders favorable changes of clinical signs, pathomechanisms, and metabolic processes that together could reduce the harm of smoking-related diseases to a relative risk level approximating that of never-smokers over time. In most SC studies, the main focus is on the quitting rate of the SC program being tested. As there is limited information in the literature on short to multiple long-term functional or biological changes following SC, more data on short to mid-term favorable impacts of SC are needed.

Objective

The overall aim of the study was to assess the reversibility of the harm related to smoking over 1 year of continuous smoking abstinence (SA). This has been verified by assessing a set of biomarkers of exposure to HPHCs and a set of biomarkers of effect indicative of multiple pathophysiological pathways underlying the development of smoking-related diseases.

Methods

This multiregional (United States, Japan, and Europe), multicenter (42 sites) cohort study consisting of a 1-year SA period in an ambulatory setting was conducted from May 2015 to May 2017. A total of 1184 male and female adult healthy smokers, willing to quit smoking, were enrolled in the study. Nicotine replacement therapy (NRT) was provided for up to 3 months upon the subject’s request. SC counseling and behavioral support were continuously provided. Biomarkers of exposure to HPHCs and biomarkers of effect were assessed in urine and blood at baseline, Month 3, Month 6, and Month 12. Cardiovascular biomarkers of effect included parameters reflecting inflammation (white blood cell), lipid metabolism (high-density lipoprotein cholesterol), endothelial function (soluble intercellular adhesion molecule-1), platelet function (11-dehydrothromboxane B2), oxidative stress (8-epi-prostaglandin F2 alpha), and carbon monoxide exposure (carboxyhemoglobin). Respiratory biomarkers of effect included lung function parameters and cough symptoms. The biomarkers of effect to evaluate genotoxicity (total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol) and xenobiotic metabolism (cytochrome P450 2A6 activity) were also assessed. Continuous SA was verified at each visit following the actual quit date using self-reporting and chemical verification. Safety assessments included adverse events and serious adverse events, body weight, vital signs, spirometry, electrocardiogram, clinical chemistry, hematology and urine analysis safety panel, physical examination, and concomitant medications.

Results

In total, 1184 subjects (50.1% male) were enrolled; 30% of them quit smoking successfully for 1 year. Data analyses of the study results are ongoing and will be published after study completion.

Conclusions

This study provides insights into biological and functional changes and health effects, after continuous SA over 1 year. Study results will be instrumental in assessing novel alternative products to cigarettes considered for tobacco harm reduction strategies.

Trial Registration

ClinicalTrials.gov NCT02432729; http://clinicaltrials.gov/ct2/show/NCT02432729 (Archived by WebCite at http://www.webcitation.org/78QxovZrr)

International Registered Report Identifier (IRRID)

DERR1-10.2196/12138

Influence of smoking on levels of urinary 8-iso Prostaglandin F2α

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Cigarette smoking is an important modifiable risk factor for cardiovascular disease.

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Cigarette smoking affects oxidative stress markers such as 8-iso prostaglandin F2α.

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The effect of smoking on urinary 8-iso prostaglandin F2α levels was meta-analyzed.

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Urinary 8-iso prostaglandin F2α levels were increased in smokers.

Background

To evaluate the reduced-risk potential of alternative tobacco products, biomarkers that are involved in the biological pathways affected by cigarette smoking and smoking cessation are needed. Isoprostanes, a measure of oxidative stress, appear to be influenced by smoking and reversible upon smoking cessation and therefore could be a good biomarker. This review aims at quantifying the effect of smoking and smoking cessation on levels of urinary 8-iso prostaglandin F_2α (8-epi-PGF_2α), an isoprostane.

Methods

PubMed and Scopus databases were searched for publications that reported 8-epi-PGF_2α levels in smokers and nonsmokers as well as articles reporting the effect of smoking cessation on 8-epi-PGF_2α levels.

Results

Eighteen studies assessing 8-epi-PGF_2α levels by smoking status were identified. Five of the papers reported the results as quantity excreted in 24-hour urine (μg/24 h), and 15 reported creatinine adjusted values. The meta-analyses show increased levels of 8-epi-PGF_2α in current smokers compared with nonsmokers (mean difference = 0.16, 95% confidence interval [95%CI]: 0.14–0.19 μg/24 h with inconsistency statistic [I²] = 98%; mean difference = 172.38, 95%CI: 152.75–192.01 pg/mg creatinine with I² = 89%, respectively). There were too few publications to perform a meta-analysis assessing the effects of smoking cessation on 8-epi-PGF_2α levels.

Conclusions

Due to the high heterogeneity among the studies included in these meta-analyses, it is difficult to generalize the results; however, our study indicates increased levels of 8-epi-PGF_2α and therefore increased oxidative stress in smokers compared with nonsmokers. More studies are still needed to assess if 8-epi-PGF_2α levels are reversible after cessation.

Evaluation of Biological and Functional Changes in Healthy Smokers Switching to the Tobacco Heating System 2.2 Versus Continued Tobacco Smoking: Protocol for a Randomized, Controlled, Multicenter Study

BACKGROUND

Tobacco harm reduction, substituting less harmful tobacco products for combustible cigarettes, is a complementary approach for smokers who would otherwise continue to smoke. The Philip Morris International (PMI) Tobacco Heating System (THS) 2.2 is a novel tobacco product with the potential to reduce the risk of harm in smokers compared to continued smoking of combustible cigarettes. It heats tobacco electrically in a controlled manner, never allowing the temperature to exceed 350°C, thereby preventing the combustion process from taking place and producing substantially lower levels of toxicants while providing nicotine, taste, ritual, and a sensory experience that closely parallels combustible cigarettes. Previous clinical studies have demonstrated reduced exposure to the toxicants (approaching the levels observed after quitting) for smokers who switched to THS 2.2, for three months. For adult smokers who would otherwise continue smoking combustible cigarettes, switching to THS 2.2 may represent an alternative way to reduce the risk of tobacco-related diseases.

OBJECTIVE

This study aimed to further substantiate the harm reduction potential of THS 2.2 by demonstrating favorable changes in a set of 8 coprimary endpoints, representative of pathomechanistic pathways (ie, inflammation, oxidative stress, lipid metabolism, respiratory function, and genotoxicity), linked to smoking-related diseases, in smokers switching from combustible cigarettes to THS 2.2.

METHODS

This study was a randomized, controlled, two-arm parallel group, multicenter ambulatory US study conducted in healthy adult smokers switching from combustible cigarettes to THS 2.2 compared with smokers continuing to smoke combustible cigarettes for six months. Subjects had a smoking history of at least ten years and did not intend to quit within the next six months.

RESULTS

Enrollment started in March 2015 and the trial was completed in September 2016. In total, 984 subjects were randomized (combustible cigarettes, n=483; THS 2.2, n=477), and 803 completed the study. The results are expected to be available in a subsequent publication in 2019.

CONCLUSIONS

In this paper, we describe the rationale and design for this clinical study that focused on the evaluation of THS 2.2's potential to reduce the risk of smoking-related diseases compared with that of combustible cigarettes. This study will provide insights regarding favorable changes in biological and functional endpoints informed by effects known to be seen upon smoking cessation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02396381; http://clinicaltrials.gov/ct2/show/NCT02396381 (Archived by WebCite at http://www.webcitation.org/71PCRdagP).

REGISTERED REPORT IDENTIFIER

RR1-10.2196/11294.

Integrating chemical, toxicological and clinical research to assess the potential of reducing health risks associated with cigarette smoking through reducing toxicant emissions

The concept of a risk continuum for tobacco and nicotine products has been proposed, which differentiates products according to their propensity to reduce toxicant exposure and risk. Cigarettes are deemed the most risky and medicinal nicotine the least. We assessed whether a Reduced-Toxicant Prototype (RTP) cigarette could sufficiently reduce exposure to toxicants versus conventional cigarettes to be considered a distinct category in the risk continuum. We present findings from both pre-clinical and clinical studies in order to examine the potential for reduced smoke toxicant emissions to lower health risks associated with cigarette smoking. We conclude that current toxicant reducing technologies are unable to reduce toxicant emissions sufficiently to manifest beneficial disease-relevant changes in smokers. These findings point to a minimum toxicant exposure standard that future potentially reduced risk products would need to meet to be considered for full biological assessment. The RTP met WHO TobReg proposed limits on cigarette toxicant emissions, however the absence of beneficial disease relevant changes in smokers after six months reduced toxicant cigarette use, does not provide evidence that these regulatory proposals will positively impact risks of smoking related diseases. Greater toxicant reductions, such as those that can be achieved in next generation products e.g. tobacco heating products and electronic cigarettes are likely to be necessary to clearly reduce risks compared with conventional cigarettes.

A Japanese cross-sectional multicentre study of biomarkers associated with cardiovascular disease in smokers and non-smokers

We performed a cross-sectional, multicentre study in Japan to detect the differences in biomarkers of exposure and cardiovascular biomarkers between smokers and non-smokers. Several clinically relevant cardiovascular biomarkers differed significantly between smokers and non-smokers, including lipid metabolism (high-density lipoprotein cholesterol concentrations – lower in smokers), inflammation (fibrinogen and white blood cell count – both higher in smokers), oxidative stress (8-epi-prostaglandin F_2α – higher in smokers) and platelet activation (11-dehydro-thromboxane B₂ – higher in smokers) (p ≤ 0.0001). These results provide further evidence showing that cardiovascular biomarkers can discriminate smokers from non-smokers, and could be used to evaluate the risks associated with tobacco products.

A cross-sectional analysis of candidate biomarkers of biological effect in smokers, never-smokers and ex-smokers

CONTEXT

Biomarkers of biological effect (BOBE) have been proposed as potential tools to assess tobacco product use, toxicity and disease risk.

OBJECTIVE

To determine if candidate BOBE can distinguish between smokers, never-smokers and former smokers.

METHODS

Biomarker levels were compared from 143 smokers, 61 never-smokers and 61 ex-smokers.

RESULTS

In total, 27 candidate biomarkers were assessed, 14 were significantly different between smokers and never-smokers (p < 0.01) and of these 14 biomarkers, 12 were able to distinguish between smokers and former smokers (p < 0.05), which indicates the potential for reversibility.

CONCLUSIONS

A total of 12 of 27 BOBE are potentially useful tools for future product assessment.

Lung cancer biomarkers for the assessment of modified risk tobacco products: an oxidative stress perspective

Manufacturers have developed prototype cigarettes yielding reduced levels of some tobacco smoke toxicants, when tested using laboratory machine smoking under standardised conditions. For the scientific assessment of modified risk tobacco products, tests that offer objective, reproducible data, which can be obtained in a much shorter time than the requirements of conventional epidemiology are needed. In this review, we consider whether biomarkers of biological effect related to oxidative stress can be used in this role. Based on published data, urinary 8-oxo-7,8-dihydro-2-deoxyguanosine, thymidine glycol, F2-isoprostanes, serum dehydroascorbic acid to ascorbic acid ratio and carotenoid concentrations show promise, while 4-hydroxynonenal requires further qualification.

Influence of cigarette smoking on synthesis of eicosanoids, isoprostanes and lipoxygenase metabolites in apical periodontitis

Arachidonic acid (AA) is metabolized to eicosanoids and isoprostanes (IPs) via different pathways. The presence of granuloma in apical periodontitis (AP) is linked with inflammation and the synthesis of metabolites of AA.

OBJECTIVE

We investigated the conversion rate of (14)C labelled arachidonic acid ((14)C-AA), the lipoxygenases (LOX) products and the endogenous synthesis of eicosanoids and IPs in extracted granuloma. Furthermore, we assessed if there are markers for bone destruction and the influence of cigarette smoking.

PATIENTS AND METHODS

In 46 patients with symptoms and corresponding radiological signs of AP, teeth were extracted including the periapical granuloma. The endogenous synthesis of eicosanoids and IPs, the conversion rate of (14)C-AA and LOX products in extracted granuloma were analyzed.

RESULTS

We found that smoking increases significantly the synthesis of IPs and LOX-metabolites in granuloma. Furthermore, smoking may have contributed to significant differences in qualitative and quantitative profile of eicosanoids, IPs and the conversion rate of (14)C-AA independent of the size of the granuloma.

CONCLUSIONS

Our data demonstrate that in smokers with granuloma due to AP products of lipid peroxidation as 8-iso-PGF(2α) and products of the LOX-pathway are increased at the expense of cyclooxygenase products. The size of granuloma did not influence the amount of synthesized eicosanoids, IPs or LOX-metabolites out of (14)C-AA whereas cigarette smoking was a significantly influencing and modifiable risk factor.

Smoking and atherosclerotic cardiovascular disease: part II: role of cigarette smoking in cardiovascular disease development

Potential mechanisms and biomarkers of atherosclerosis related to cigarette smoking - a modifiable risk factor for that disease - are discussed in this article. These include smoking-associated inflammatory markers, such as leukocytes, high-sensitivity C-reactive protein, serum amyloid A, ICAM-1 and IL-6. Other reviewed markers are indicative for smoking-related impairment of arterial endothelial function (transcapillary leakage of albumin, inhibition of endogenous nitric oxide synthase activity and reduced endothelium-dependent vasodilation) or point to oxidative stress caused by various chemicals (cholesterol oxidation, autoantibodies to oxidized low-density lipoprotein, plasma levels of malondialdehyde and F(2)-isoprostanes and reduced antioxidant capacity). Smoking enhances platelet aggregability, increases blood viscosity and shifts the pro- and antithrombotic balance towards increased coagulability (e.g., fibrinogen, von Willebrand factor, ICAM-1 and P-selectin). Insulin resistance is higher in smokers compared with nonsmokers, and hemoglobin A1c is dose-dependently elevated, as is homocysteine. Smoke exposure may influence the kinetics of markers with different response to transient or chronic changes in cigarette smoking behavior.

The role of exercise in minimizing postprandial oxidative stress in cigarette smokers

Cigarette smoking continues to pose a significant health burden on society. Two well-described mechanistic links associating smoking with morbidity and mortality include elevated blood lipids and increased oxidative stress. These variables have traditionally been measured while an individual is fasting, but evidence suggests that postprandial lipemia and oxidative stress provide more important information concerning susceptibility to disease, in particular cardiovascular disease. Cigarette smokers have elevated levels of biomarkers of oxidative stress at rest and experience impaired postprandial lipid and glucose metabolism. We have confirmed these findings while noting an exaggerated oxidative stress response to high-fat feeding. Smoking cessation is without question the best approach to minimizing smoking-induced ill health and disease, but success rates among those who attempt to quit are dismal. Other means to decrease a smoker's susceptibility to oxidative stress-related disease are needed. We propose that exercise may aid in attenuating postprandial oxidative stress, and we do so in 3 distinct ways. First, exercise stimulates an increase in endogenous antioxidant enzyme activity. Second, exercise improves blood triglyceride clearance via a reduced chylomicron-triglyceride half-life and an enhanced lipoprotein lipase activity. Third, exercise improves blood glucose clearance via an enhanced glucose 4 transport protein translocation and protein content, as well as insulin-insulin receptor binding and postreceptor signaling. Improvements in antioxidant status, as well as lipid and glucose processing, may aid greatly in minimizing feeding-induced oxidative stress in smokers. If so, and in accordance with the recent joint initiative of the American College of Sports Medicine and the American Medical Association, exercise may be viewed as a "medicine" for cigarette smokers at increased risk for postprandial oxidative stress. Research into this area may provide insight into the potential benefits of exercise for this purpose.

Postprandial oxidative stress in exercise trained and sedentary cigarette smokers

Cigarette smokers experience an exaggerated triglyceride (TAG) and oxidative stress response to high fat feeding. Exercise training may serve to attenuate the rise in these variables, by improving TAG clearance and antioxidant defense. We compared blood TAG, antioxidant capacity, and oxidative stress biomarkers in exercise trained (>2 hrs per wk) and untrained smokers matched for age, in response to a high fat test meal. We report here that low volume exercise training can attenuate postprandial lipid peroxidation, but has little impact on blood TAG and other markers of oxidative stress. Higher volumes of exercise may be needed to allow for clinically meaningful adaptations in postprandial lipemia and oxidative stress.

Quantitation of isoprostane isomers in human urine from smokers and nonsmokers by LC-MS/MS

A simple, rapid liquid chromatography-tandem mass spectrometry method was developed to identify and quantitate in human urine the isoprostanes iPF(2 alpha)-III, 15-epi-iPF(2 alpha)-III, iPF(2 alpha)-VI, and 8,12-iso-iPF(2 alpha)-VI along with the prostaglandin PGF(2 alpha) and 2,3-dinor-iPF(2 alpha)-III, a metabolite of iPF(2 alpha)-III. Assay specificity, linearity, precision, and accuracy met the required criteria for most analytes. The urine sample storage stability and standard solution stability were also tested. The methodology was applied to analyze 24 h urine samples collected from smokers and nonsmokers on controlled diets. The results for iPF(2 alpha)-III obtained by our method were significantly correlated with results by an ELISA, although an approximately 2-fold high bias was observed for the ELISA data. For iPF(2 alpha)-III and its metabolite 2,3-dinor-iPF(2 alpha)-III, smokers had significantly higher concentrations than nonsmokers (513 +/- 275 vs. 294 +/- 104 pg/mg creatinine; 3,030 +/- 1,546 vs. 2,046 +/- 836 pg/mg creatinine, respectively). The concentration of iPF(2 alpha)-VI tended to be higher in smokers than in nonsmokers; however, the increase was not statistically significant in this sample set. Concentrations of the other three isoprostane isomers showed no trends toward differences between smokers and nonsmokers. Among smokers, the daily output of two type VI isoprostanes showed a weak correlation with the amount of tobacco smoke exposure, as determined by urinary excretion of total nicotine equivalents.

Oxidative stress in children receiving valproic acid

OBJECTIVE

To determine whether valproic acid (VPA) influences urinary levels of 15-F2t -isoprostane (15-F2t -IsoP), a marker of oxidative stress, in children.

STUDY DESIGN

Morning urine samples were collected from children with epilepsy receiving VPA (n = 25), carbamazepine (n = 16), or clobazam (n = 12) for > or = 4 weeks and from age-matched control subjects (n = 39). Urinary 15-F2t -IsoP levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The mean (+/- standard deviation) urine 15-F2t -IsoP levels (nmol/mmol Cr) were: valproic acid (0.36 +/- 0.15); carbamazepine (0.24 +/- 0.10); clobazam (0.23 +/- 0.10); control group (0.20 +/- 0.09). Patients treated with VPA had significantly elevated 15-F2t -IsoP levels when compared with the control, carbamazepine, and clobazam groups (P < .05). Multiple linear regression analysis demonstrated that younger patient age and exposure to second-hand smoke were significant predictors of elevated urine 15-F2t -IsoP levels within the control group (r2 = 0.261, P = .05 and P = .01, respectively). Subjects not exposed to second-hand smoke receiving valproic acid therapy had a significantly elevated mean urine 15-F2t -IsoP level compared to subjects not exposed to second-hand smoke in the carbamazepine, clobazam and control groups (P < .05).

CONCLUSIONS

These data demonstrate that treatment of children with VPA is associated with higher urinary levels of 15-F2t -IsoP, a marker of oxidative stress.

Cardiovascular pharmacology and physiology of the isoprostanes

F(2)-isoprostanes are a complex family of compounds produced from arachidonic acid via a free radical-catalyzed mechanism. Their quantification as a pathophysiological biomarker provides a unique opportunity to investigate lipid peroxidation in vascular diseases. Their measurement also provides an interesting biomarker for the rational dose selection of antioxidants in vascular diseases where oxidative stress might be involved. In addition to their use as biomarkers, some isoprostanes possess a biological activity. The 15-series F(2)- and E(2)-isoprostanes mediate vasoconstriction in different vascular beds and species. In addition, 15-F(2t)-IsoP induces smooth muscle cells mitogenesis and monocyte adhesion to endothelial cells. The data available supports but does not prove the hypothesis that isoprostanes are involved in vascular physiology and pathogenesis.

An approach to the validation of biomarkers of harm for use in a tobacco context

There is both a call and a need for biomarkers of harm that are validated for use in a tobacco context. Currently, there are no validated biomarkers and there is no consensus about which ones may be suitable for this purpose. To advance the science in this area a working definition of biomarkers of harm and a shortlist of candidate biomarkers are proposed. A framework for the validation of biomarkers of harm using of a series of epidemiological studies culminating in a targeted prospective study is outlined. The candidate biomarkers have advanced to preliminary testing although this does not imply that any on the shortlist will become validated. This framework could also be used for the evaluation of proteomic, genomic, transcriptosomic or metabonomic profiles, which may turn out to be the preferred biomarkers for use in harm prediction. Biomarker studies would complement data that are generated from specific in vitro tests and from animal studies to evaluate tobacco products.

Salivary isoprostanes indicate increased oxidation injury in periodontitis with additional tobacco abuse

Isoprostanes (IPs) are indicators of in-vivo oxidative stress, and have been successfully used as markers for chronic inflammatory processes. The presence of chronic periodontal disease and cigarette smoking has been individually linked to the development of atherosclerosis, yet data regarding oxidative stress in this context are not available yet. The aim of this study was to evaluate levels of the salivary prostaglandins (PGs) 8-epi-PGF(2alpha), 6-oxo-PGF(1alpha), thromboxane B(2) (TXB(2)) and PGF(2alpha) in association with periodontal disease status with and without additional cigarette smoking. We analyzed saliva samples from 121 adults, (aged 21-73 years, 90 non-smokers, 31 smokers) for levels of 8-epi-PGF(2alpha), 6-oxo-PGF(1alpha), TXB(2) and PGF(2alpha). On the basis of periodontal disease indices the periodontal status of each subject was assessed and outcomes were then correlated with smoking status and laboratory findings. Salivary 8-epi-PGF(2alpha) levels increased with deteriorating plaque index, and were significantly higher (115.5 +/- 23.5 pg/ml) in smoking individuals, when compared to non-smokers (70.2 +/- 20.4 pg/ml, p<0.0001). In addition, smokers showed higher TXB(2) and PGF(2alphas) and lower 6-oxo-PGF(1alpha) levels p<0.0001). Oxidative stress, as reflected by elevated salivary 8-epi-PGF(2alpha) levels, is associated with the extent of periodontal disease and is significantly aggravated by concomitant tobacco abuse. Chronic inflammation and smoking have been individually associated with the development of atherosclerosis. The results of this study indicate that: 1) salivary IPs can reliably assess the degree of oxidative stress, and: 2) smoking and periodontal disease are two modifiable cardiovascular risk factors, able to potentiate each other.

Urinary 8-isoprostaglandin F(2alpha) level in Behçet's disease

Although its etiology remains unknown, the increased production of reactive oxygen species in Behçet's disease (BD) have been reported. Furthermore, it has been suggested that vascular and endothelial tissue damage seen in BD is related to elevated reactive oxygen species generated by activated neutrophils from BD patients. To investigate the formation of lipid peroxidation in BD patients in vivo, urinary level of 8-isoprostaglandin F(2alpha) was quantitated by enzyme immunoassay after solid phase extraction in different clinical forms of BD patients. There was no difference in urinary level of 8-isoprostaglandin F(2alpha) between BD patient and healthy control group. There was also no difference in urinary levels of 8-isoprostaglandin F(2alpha) in subgroup analyses of BD patients, i.e. in mucocutaneous and vascular type BD patients; active and inactive BD patients. Contrary to the findings in literature, we found no difference in urinary level of 8-isoprostaglandin F(2alpha) between patients with systemic lupus erythematosus and healthy control group. These findings show no increase in lipid peroxidation despite the augmented formation of reactive oxygen species in BD patients. It may be interesting to assess formation of urinary level of 8-isoprostaglandin F(2alpha) in BD patients who do not take any medication.

Isoprostanes: novel bioactive products of lipid peroxidation

Isoprostanes, are a novel group of prostaglandin-like compounds that are biosynthesised from esterified polyunsaturated fatty acid (PUFA) through a non-enzymatic free radical-catalysed reaction. Several of these compounds possess potent biological activity, as evidenced mainly through their pulmonary and renal vasoconstrictive effects, and have short half-lives. It has been shown that isoprostanes act as full or partial agonists through thromboxane receptors. Both human and experimental studies have indicated associations of isoprostanes and severe inflammatory conditions, ischemia-reperfusion, diabetes and atherosclerosis. Reports have shown that F2-isoprostanes are authentic biomarkers of lipid peroxidation and can be used as potential in vivo indicators of oxidant stress in various clinical conditions, as well as in evaluations of antioxidants or drugs for their free radical-scavenging properties. Higher levels of F2-isoprostanes have been found in the normal human pregnancy compared to non-pregnancy, but their physiological role has not been well studied so far. Since bioactive F2-isoprostanes are continuously formed in various tissues and large amounts of these potent compounds are found unmetabolised in their free acid form in the urine in normal basal conditions with a wide inter-individual variation, their role in the regulation of normal physiological functions could be of further biological interest, but has yet to be disclosed. Their potent biological activity has attracted great attention among scientists, since these compounds are found in humans and animals in both physiological and pathological conditions and can be used as reliable biomarkers of lipid peroxidation.

Application of gas chromatography-mass spectrometry for analysis of isoprostanes: their role in cardiovascular disease

Cardiovascular disease (CVD) is the major cause of death in the Western hemisphere. Oxidative stress is involved in the pathophysiology of cancer, neurodegenerative conditions and CVD. Lipid peroxidation is one of the oxidative modifications possible in biological systems. The isoprostanes are derivatives of one specific lipid, i.e., arachidonic acid, after lipid peroxidation. Several isoprostanes have been identified in biological tissues and fluids, among them 8-iso prostaglandin F2alpha (8-iso-PGF2alpha, 8-epi-PGF2alpha, iPF2alpha-III, 15-F2t-IsoP) and its metabolite, 2,3-dinor-4,5-dihydro-8-iso-PGF2alpha. The isoprostanes are reliable in vivo markers of lipid peroxidation in humans: they are endogenously formed, characteristic in structure, ubiquitous in nature, stable in- and ex vivo and reliably quantitatable. In this Review, different analytical approaches will be discussed including immunologic, chromatographic and spectrometric techniques with the main emphasis on mass spectrometry. Analysis of isoprostanes applying radio immunoassay (RIA), enzyme immunoassay (EIA), high performance-liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-tandem MS), gas chromatography-mass spectrometry (GC-MS) and GC-tandem MS will be exemplified in the field of cardiovascular research. Results from several clinical studies are included indicating the validity of isoprostanes as surrogate parameters of oxidative stress in cardiovascular disease.

Isoprostanes: an emerging role in vascular physiology and disease?

Among the isoprostanes, the 15-series F2-isoprostanes and 15-E2t-IsoP mediate vasoconstriction in different vascular beds and species. In addition, 15-F2t-IsoP induces smooth muscle cells mitogenesis and monocyte adhesion to endothelial cells. In clinical studies, 15-F2t-IsoP levels are increased in some vascular disorders involving atherosclerosis, ischemia-reperfusion and inflammation. Whether the same effects observed in vitro are observed consistently in vivo at physiological concentrations and whether these effects contribute to pathological states in vivo is still debated.

Narghile (water pipe) smoking influences platelet function and (iso-)eicosanoids

The biological effects of smoking water pipe on haemostasis and the eicosanoid system is unknown. Water pipe smoking is familiar to approximately 1 billion people around the world. Considering this quite impressive number, we investigated the potential effect of smoking the Narghile on oxidation injury by monitoring parameters of the (iso)eicosanoid system. Patients were allowed to smoke a water pipe once daily for 14 days. Blood was drawn from 7 healthy adult non-cigarette smoking male volunteers before and immediately after the first smoking of the water pipe and additionally after 6 hours. One and 2 weeks thereafter, blood was drawn again before and after smoking. A total of 7 blood samples was drawn during the study, and parameters of in vivo oxidation injury (8-epi-PGF2alpha, malondialdehyde [MDA]) and haemostasis (11-dehydro-thromboxane B2 [11-DH-TXB2]) were investigated. A single smoking session increased oxidation injury (8-epi-PGF2alpha: p=0.03; MDA: p=0.001) and 11-DH-TXB2 (p=0.00003) significantly, and repeated daily smoking induced a persistent long-lasting oxidation injury reflected by elevated prevalues but a smaller response to the actual water pipe smoke. These findings indicate a significant increase of in vivo oxidative stress by regular water pipe smoking.

Isoprostanes as a biomarker of lipid peroxidation in humans: physiology, pharmacology and clinical implications

Isoprostanes are a complex family of compounds produced from arachidonic acid via a free-radical-catalyzed mechanism. They can be quantified as reliable markers of lipid peroxidation. Among the isoprostanes, 15-F(2t)-IsoP and 15-E(2t)-IsoP are biologically active and mediate vasoconstriction and bronchoconstriction and augment nociception. These effects are thought to be mediated via the activation of prostanoid TP receptors, with isoprostanes acting as full or partial agonists. A strong link between lipid peroxidation and diseases associated with ischaemia-reperfusion, atherosclerosis and inflammation has been suggested by elevated levels of F(2)-isoprostanes observed in such diseases. Thus, quantification of F(2)-isoprostanes as a pathophysiological marker provides a unique opportunity to investigate lipid peroxidation in human diseases and provides an interesting biomarker for rational dose selection of antioxidants in diseases where oxidative stress might be involved.

Isoprostane 8-epi-PGF2alpha is frequently increased in patients with muscle pain and/or CK-elevation after HMG-Co-enzyme-A-reductase inhibitor therapy

BACKGROUND

Muscle pains with or without CK-elevation are among the most frequently observed side-effects in patients with hyperlipoproteinemia on various statins. The pathophysiological background, however, remains obscure.

METHODS

We examined isoprostane 8-epi-PGF2alpha, a marker of in-vivo oxidation injury, in plasma, serum and urine in these patients at baseline, when muscle problems manifested and different time intervals after withdrawing the respective statin. A healthy control group and a group of untreated patients with hyperlipoproteinemia were run as controls.

RESULTS

The majority of patients with muscular side-effects show elevated 8-epi-PGF2alpha in plasma and urine, whereas serum values were elevated only to a lesser extent. Stopping statin therapy or successfully changing to another member of this family of compounds resulted in a normalization of the values in all patients.

CONCLUSION

These findings indicate a significant involvement of oxidative injury in the muscular side-effects of statins in patients suffering from hyperlipoproteinemia.