Salivary Malondialdeyde and antioxidant status


Oral sqamous cell carcinoma is the sixth most common cancer in men and the 14th most common cancer in women. On an average only half of those diagnosed with this disease will survive more than five years. Free radicals such as reactive oxygen species (ROS) and reactive nitrogen species(RNS), which induce oxidative and nitrative stress are principal inducers of OSCC. ROS such as superoxide radicals (O2), hydroxyl radicals(OH.) hydrogen peroxide (H2O2) and RNS in the form of nitrosamines (NO3 and NO2) play a key role in human cancer development. Reactive free radicals are able to damage proteins, lipids, carbohydrates and nucleotides in the tissue. ROS can cause DNA base alterations, strand breaks, damage tumor suppressor genes and enhance expression of proto oncogenes. The OSCC inducing ROS and RNS originate mainly from smoking, alcohol, food and drink which enter into the oral cavity through the mouth. The oral cavity is armed with salivary antioxidant system containing both enzymatic and nonenzymatic components including peroxidase, superoxide dismutase, glutathione s-transferase and uric acid.

Saliva is a diagnostic tool for many oral and systemic diseases. Moreover reports on salivary antioxidants are very scanty. Therefore the current study was planned to evaluate the oxidative stress and antioxidant profile of the saliva in OSCC patients and smokers. Malondialdehyde (MDA) was estimated as the marker of lipid peroxidation. Uric acid, vitamin C and total antioxidant activity (TAA) was measured to assess the antioxidant status of OSCC patients, smokers and controls.

The salivary pH test is a simple test to measure the susceptibility of cancer, heart disease and many other degenerative diseases. Since the pH of saliva offers us a window through which we can see the overall pH balance in the body, we have also measured the pH of saliva of all the subjects enrolled in the present study.

Free radical mediated oxidative stress has been implicated in pathogenesis of Oral Squamous Cell Carcinoma (OSCC). The present study was conducted in saliva to estimate the level of lipid peroxidation product- malondialdehyde ( MDA) and antioxidants uric acid, vitamin C, and total antioxidant activity in 25 OSCC patients. The results were compared with age and sex matched 25 smokers and 25 normal healthy control subjects. pH of the saliva was also measured in all the study groups. Highly significant increase in MDA and decrease in antioxidants was observed in OSCC patients and smokers. pH of saliva decreased significantly in smokers. This study suggests that there is increased oxidative stress and antioxidant defense mechanism is impaired in OSCC patients and smokers. Supplementation of antioxidants might be beneficial to reduce the oxidative stress in OSCC patients and smokers.

Reactive free radicals are able to produce chemical modifications and damage to proteins, lipids, carbohydrates and nucleotides in the tissues. It is also known that free radicals are mediators for tissue damage in neoplastic diseases. The development of cancer is multifactorial, depending on the extent on DNA damage that is proportional to the magnitude of oxidative stress. This oxidative stress reflects the net effect of ROS on the one hand and the effectiveness of antioxidant defense on the other. ROS is involved in the initiation and promotion of multistep carcinogenesis but it is inhibited by antioxidants. When this equilibrium is broken either by a reduction in the levels of antioxidants or by enhancement of ROS, the DNA is oxidized and cancer evolves. In our study we have found that MDA which is the marker for oxidative stress is highly increased in OSCC patients. Moreover the antioxidants like uric acid , vitamin c and total antioxidant activities are greatly reduced in these patients. Uric acid which is the end product of purine metabolism has been regarded as the potent endogenous water soluble antioxidant in saliva and free radical scavenger in humans. Uric acid is particularly effective in quenching hydroxyl superoxide and peroxynitrite radicals and may serve a protective role by preventing lipid peroxidation. Uric acid and total antioxidant activity is significantly reduced in OSCC patients which indicates that antioxidant defense is impaired in the saliva of oral squamous cell carcinoma patients.

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