Evaluation of oxidative stress markers and antioxidant status in smokers

Abstract               Aims and objective: Evaluation of oxidative stress markers and antioxidant status in Smokers. Material and methods: Study was conducted in Department of Biochemistry, LTMMC Sion Mumbai. 60 chronic smokers were tested for levels of MDA (Malondialdehyde), GSH (Glutathione) and SOD (Superoxide dismutase). Results were compared with 60 controls. Results and observations: Samples from patients showed increased MDA and decreased values of SOD and GSH when compared with controls and results were statistically significant. Discussion: Oxidative stress is harmful condition that occurs when there is excess of reactive oxygen species or decreased antioxidant level. It is evident from results that smoking increases the oxidative stress and decreases antioxidant level in smokers as compared to controls.

Key Word: cigarette smoking, antioxidants.

INTRODUCTION

Cigarette smoking is a serious health problem and most important avoidable cause of death in world. A single cigarette puff contains approx. 10³⁰ free radicals. These are capable of causing an increase in generation of various ROS¹ like superoxide⁴ (O₂^.-), Hydrogen peroxide (H₂O₂), Hydroxyl (OH^-) and Peroxyl (ROO^.) radicals which in turn lead to oxidative damage causing different diseases like Parkinsonism, Diabetes, Cancer, Bronchitis, COPD etc. Anti-oxidants² are substances that delay or inhibit oxidative damage to the target molecule and prevent cell and tissue damage. An imbalance between the oxidants and the antioxidants leads to oxidative stress which is characterized by escalating cell damage.^3,4 Malondialdehyde (MDA) is a product and hence a marker of the oxidative stress mediated lipid peroxidation. Superoxide dismutase functions as a scavenger of superoxide radical in the body. Reduced glutathione (GSH) is one of the frontline non-enzymatic intracellular antioxidant which safeguards against the oxidative insults.

MATERIALS AND METHODS

This study was done in Department of Biochemistry, in tertiary care centre. The Institutional Ethics Committee approved the study. The volunteers were fully informed of the nature and purpose of the study and written consent was obtained from each. The blood samples were collected from 60 smokers and 60 non smoker controls to analyze oxidative stress. Oxidative stress was estimated with the help of parameters such as serum MDA, serum SOD and whole blood GSH. Student t test was applied to analyze the statistical data.

Estimation of serum MDA⁶: Serum MDA was estimated using modified method of sadasivudu et al, 1999. The activity was expressed in nmol/ml.

Estimation of serum SOD⁵: Serum SOD was estimated by Marklund and Marklund method modified by Nandi et al.⁸ The activity was expressed in u/ml.

Estimation of whole blood GSH⁷: Whole blood GSH was estimated by Beutler E et al method. The activity was expressed in mg/dl.

Statistical analysis: For each parameter studied, mean and standard deviation was calculated to estimate the significance. The difference between the groups was measured by Students Unpaired ‘t’ test. P Value less than 0.05 considered as statistically significant. The calculations were performed using the statistical program SPSS for Windows Version 13, with a p value of < 0.05 considered significant.

RESULTS AND DISCUSSION

Oxidative stress is harmful condition that occurs when there is excess of reactive oxygen species or decreased antioxidant level. Superoxide dismutase functions as a scavenger of superoxide radical in the body. The level of SOD is decreased in oxidative stress, which plays an important role in the pathogenesis of various disease.⁹ GSH plays a significant role in the detoxification of the xenobiotic and in the maintenance of the redox status of the cells.^4,12 Under non stress conditions, most of the intracellular glutathione is stored in the reduced form (GSH). During increased oxidative stress, the free sulfhydryl (-SH) groups become oxidized resulting in loss of GSH. The gaseous phase of cigarette smoke may also irreversibly react with GSH to form GSH derivatives that cannot be reduced back, thereby depleting the total available GSH pool.^10,11 Malondialdehyde is an easily detectable biomarker of oxidative stress. MDA is a lipid peroxidation product which is formed during oxidative process of PUFA by reactive oxygen species. Smokers are subjected to increased oxidative stress and hence increased level of MDA.¹¹ It is evident from results that Smoking increases the oxidative stress and decreases antioxidant level (reduced SOD, GSH and increased MDA) in smokers compared to normal controls.

CONCLUSION

Smoking causes increase in oxidative stress and consequently decreases the antioxidants. Antioxidants by scavenging the free radicals reduces the process of lipid peroxidation thus prevents further consequences.

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