|Year : 2012 | Volume
| Issue : 2 | Page : 114-119
Superoxide dismutase and glutathione peroxidase in oral submucous fibrosis, oral leukoplakia, and oral cancer: A comparative study
Shubha Gurudath1, Raghavendra Mahadev Naik2, KS Ganapathy1, Yadavalli Guruprasad3, D Sujatha1, Anuradha Pai1
1 Department of Oral Medicine and Radiology, Oxford Dental College and Hospital, Bangalore, Karnataka, India
2 Department of Oral Medicine and Radiology, Vishnu Dental College and Hospital, Bhimavaram, Andhra Pradesh, India
3 Department of Oral and Maxillofacial Surgery, AME'S Dental College Hospital and Research Centre, Raichur, Karnataka, India
|Date of Web Publication||17-Jan-2013|
Department of Oral and Maxillofacial Surgery, AME'S Dental College Hospital and Research Centre, Raichur - 584 103, Karnataka
Source of Support: None, Conflict of Interest: None
Objectives: Present study was undertaken to estimate and compare erythrocyte superoxide dismutase (E-SOD) and glutathione peroxidase (GPx) levels in oral submucous fibrosis, oral leukoplakia, oral cancer patients, and healthy subjects. Materials and Methods: E-SOD and GPx levels were estimated in OSF, oral leukoplakia, and oral cancer patients with 25 subjects in each group. The results obtained were compared with the corresponding age-/sex- matched control groups. Results: Statistically significant ( P < 0.001) decrease in E-SOD and GPx levels were observed in OSF, oral leukoplakia, and oral cancer groups as compared to the control group. Oral leukoplakia group showed lower levels in comparison with OSF ( P > 0.05). Oral cancer group had the lowest levels amongst the study groups. Conclusion: Imbalance in antioxidant enzyme status may be considered as one of the factors responsible for the pathogenesis of cancer and may serve as a potential biomarker and therapeutic target to reduce the malignant transformation in oral premalignant lesions/conditions.
Keywords: Gglutathione peroxidase, oral cancer, oral leukoplakia, oral submucous fibrosis, reactive oxygen species, superoxide dismutase
|How to cite this article:|
Gurudath S, Naik RM, Ganapathy K S, Guruprasad Y, Sujatha D, Pai A. Superoxide dismutase and glutathione peroxidase in oral submucous fibrosis, oral leukoplakia, and oral cancer: A comparative study. J Orofac Sci 2012;4:114-9
|How to cite this URL:|
Gurudath S, Naik RM, Ganapathy K S, Guruprasad Y, Sujatha D, Pai A. Superoxide dismutase and glutathione peroxidase in oral submucous fibrosis, oral leukoplakia, and oral cancer: A comparative study. J Orofac Sci [serial online] 2012 [cited 2017 Apr 27];4:114-9. Available from: http://www.jofs.in/text.asp?2012/4/2/114/106202
| Introduction|| |
Oral squamous cell carcinoma (OSCC) is one of the most common cancers in the world, often preceded by specific pre-malignant lesions or conditions, the most common amongst them are the oral leukoplakia and oral submucous fibrosis. Well-known risk factors are consumption of tobacco, areca nut, and alcohol, which result in increased free radicals production. Reactive oxygen species (ROS) and free radicals are conjectured to be involved in neoplastic transformation. 
ROS cause chemical modification in the cells by causing damage to proteins, lipids, carbohydrates, and nucleotides. An imbalance between the production of ROS and the cell's oxidant capacity creates oxidative stress, which in turn may instigate or promote carcinogenesis in the cell by mutagenesis, cytotoxicity, and changes in gene expression. Thus, free radicals are believed to play an elementary role in the disease progression.  A number of compounds and enzymes function to overcome the consequences of ROS and to protect cellular components from oxidative damage. Antioxidants are the first line of defense against free radical damage and are essential for maintaining optimum health and well-being. Superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) are the three major enzymatic antioxidant defense systems responsible for scavenging free radicals and nascent oxygen.  Antioxidant enzymes catalyze decomposition of ROS. Redox modulation is seen by distinctive changes in the activities of these enzyme systems in oxidative stress. Thus, an overall balance between production and removal of ROS may be more important in various cancers including OSCC. 
Despite therapeutic and diagnostic advances, the rate at which oral pre-cancerous and cancerous lesions are spreading is alarming. This highlights the need for continued efforts to discover suitable biomarkers for early diagnosis. In spite of high prevalence of OSF and oral leukoplakia in India and their potential to undergo malignant transformation, the antioxidant status of these individuals has not been widely investigated. Moreover, to the best of our knowledge, literature on the antioxidant status in relation to pre-malignant lesion or condition is scarce. With this view in mind, this study was undertaken to investigate and compare the bio-chemical alterations in the sera of oral pre-cancer, oral cancer, and healthy subjects.
| Materials and Methods|| |
The study was designed with 25 newly-diagnosed patients with oral submucous fibrosis, oral leukoplakia, and oral cancer, who were not been previously treated for the same. A provisional diagnosis of leukoplakia was made when a predominantly white lesion at clinical examination cannot be clearly diagnosed as any other disease or disorder of the oral mucosa [Figure 1]. Biopsy was performed, and a definitive diagnosis was made when any etiological cause other than tobacco⁄areca nut use has been excluded and histopathology has not confirmed any other specific disorder.  Oral leukoplakia lesion size ranged from 1 × 1 to 3 × 4 cms. Control groups consisted of 25 healthy, age-/sex-matched subjects (Control A) for OSF and oral leukoplakia; and another control group (Control B) for oral cancer. Samples were randomly recruited based on the selection criteria, amongst the out-patients visiting department of oral medicine and radiology.
|Figure 1: Intra-oral photograph showing white patch, with crack mud appearance on the left buccal mucosa, suggestive of homogenous leukoplakia|
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- Patients clinically and histopathologically diagnosed with oral submucous fibrosis, oral leukoplakia, and oral cancer
- Patients not on any treatment for the same
- Patients who agreed for the biopsy and hematological examination
- Normal subjects without any oral lesions and systemic diseases.
All subjects were interviewed before being clinically examined in the out-patient department. The questionnaire contained data on demographic factors, types of habits, frequency, and duration of habits. All the study group patients, i.e. the OSF group patients were regular areca nut (gutka) chewers (average of about 3-5 years). Oral leukoplakia [Figure 2], [Figure 3] and [Figure 4] and oral cancer patients [Figure 5], [Figure 6] and [Figure 7] were regular and active smokers, tobacco chewers, and/or alcoholics. Oral leukoplakia lesions included in the study varied from 1 × 1 cm to 3 × 4 cm in size. The clinical and pathological diagnosis was subsequently recorded [Table 1]. This protocol was approved by the ethical committee of the Institutional Review Broad (IRB) to proceed with the research. Study protocol was explained, and an informed consent was obtained from the patients.
- Patients below the age of 18 and above 65 years
- Patients suffering from any systemic diseases like diabetes, hypertension, cardiovascular diseases, renal dysfunction, or liver disorders
- Patients with previous history of treatment for the same conditions.
|Figure 2: Histopathological photomicrograph showing area of increased epithelial thickness together with hyperkeratosis, suggestive of mild dysplasia. (H and E, x10)|
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|Figure 3: Histopathological photomicrograph showing squamous hyperparakeratosis blunt and elongated epithelial ridges and cytonuclear atypia confined to the lower epithelial half, suggestive of moderate dysplasia. (H and E, x10)|
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|Figure 4: Histopathological photomicrograph showing epithelial alterations involving the entire epithelial thickness, suggestive of severe dysplasia. (H and E, x10)|
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|Figure 5: Intraoral photograph showing ulceroproliferative growth with indurated margins on the left buccal mucosa, suggestive of carcinoma|
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|Figure 6: Histopathological photomicrograph showing presence of "pearls" (keratinized epithelium), suggestive of well-differentiated squamous cell carcinoma. (H and E, x10)|
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|Figure 7: Histopathological photomicrograph showing presence of "pearls" (keratinized epithelium), suggestive of moderately differentiated squamous cell carcinoma. (H and E, x10)|
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Under aseptic condition, 5 ml overnight fasting venous blood was obtained from the antecubital vein using sterile disposable syringe and was stored in heparinized vacutainer tubes. Serum was separated in 2.5 ml of blood by centrifugation (3000 rpm for 15 mins). The red blood cell (RBC) pellet was then washed three times with sterile saline to ensure complete removal of the plasma, leucocytes, and platelets. The washed RBCs were hemolyzed by the addition of sterile distilled water (1:5). Then, the lysate was centrifuged at 3000 rpm for 15 min in order to make the lysate ghost-free. The supernatant and remaining 2.5 ml of heparinized whole blood was stored at -70° C until analysis. Estimation of both the enzymes E-SOD and GPx were determined by Ransel anti-oxidant enzyme kit provided by RANDOX Laboratories Ltd (Antrim, United Kingdom), and samples were processed on Bayer RA-50 chemistry analyzer for spectrometry.
Superoxide dismutase assay
Total E-SOD cytosol and hemolysate was assayed based on the inhibition of a superoxide-induced NADH oxidation. The decrease in the rate of NADH oxidation is dependent on the enzyme concentration, and saturation levels were attainable by recording the corresponding readings, spectrophotometrically (520 nm). Normal E-SOD level: 164-240 U/ml. 
Glutathione peroxidase assay
Estimation of GPx activity in cytosol and hemolysate was based on the method of Paglia and Valentine using hydrogen peroxide and the rate of disappearance of NADPH at 37° C and was recorded spectrophotometrically (340 nm). Normal GPx level: 27.5-73.6 U/g Hb. 
The quantified variables in the study (age, sex, superoxide dismutase, and glutathione peroxidise levels) were subjected to statistical analysis. All these values were analyzed for mean, standard deviation, errors, and range. The data were statistically analyzed using SPSS (Version 17) statistical software. Unpaired Student′s ′t′ test was performed to compare the levels between control and study groups. P value is less than 0.05 was considered significant.
| Results|| |
The mean age in OSF, oral leukoplakia, oral cancer group was found to be 32.33 ± 9.01, 40.73 ± 9.65, and 53.73 ± 6.19 years, which reflects the subject population mostly being affected. All groups consisted of 20 (80%) males and 5 (20%) females, respectively [Table 1].
The mean E-SOD level of OSF, oral leukoplakia, and oral cancer group was 104.35 ± 27.42 U/ml; 91.52 ± 19.45 U/ml and 49.75 ± 7.88 U/ml, respectively. The mean GPx level of OSF, oral leukoplakia, and oral cancer group was 23.03 ± 2.46 U/gHb; 21.55 ± 2.36 U/gHb, and 11.37 ± 1.47 U/gHb, respectively. All patients in the control group had E-SOD (164-240 U/ml) and GPx (27.5 -73.6 U/g Hb) levels within the normal range.
[Table 2] and [Table 3] shows a statistically significant (P < 0.001) decrease of mean E-SOD and GPx levels in OSF, oral leukoplakia, and oral cancer patients when compared with the corresponding control groups. Lower mean E-SOD and GPx values were observed in oral leukoplakia group in comparison with OSF group, but the difference observed was not statistically significant (P > 0.05). A statistically significant difference was observed (P < 0.001) with higher mean E-SOD and GPx values in OSF and oral leukoplakia in comparison with oral cancer group. Thus, oral cancer group showed the lowest mean E-SOD and GPx levels amongst the study groups.
|Table 2: Comparison of mean superoxide dismutase levels between study and control groups|
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|Table 3: Comparison of mean glutathione peroxide levels between study and control groups|
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| Discussion|| |
A male proclivity is observed in the present study groups consisting 20 males (80%) and 5 females (20%); who had tobacco, areca nut, betel quid chewing, alcohol consumption, and other habits. Earlier studies have shown that these habits have clastogenic and carcinogenic effects.  The fundamental hypothesis is, free radicals damage the cellular materials, which would result in triggering or transforming normal cells into malignant ones. But, the magnitude of such damage is dependent on the body's defense mechanism, which is mediated by various cellular antioxidants. The two verified mechanisms favoring radical alteration of ROS metabolism in cancer cells are production of huge amounts of ROS compared with non-neoplastic cells and suppression of antioxidant system. 
Antioxidant enzymes such as E-SOD and GPx can directly counterbalance the oxidant attack and protect the cells against DNA damage. Superoxide dismutase is a decisive antioxidant enzyme in aerobic cells, which is responsible for the elimination of superoxide radicals. E-SOD converts two toxic species: Superoxide (O 2• - ) and hydrogen peroxide (H 2 O 2 ) into water. This diminishes the toxic effects of superoxide radical and other radicals formed by secondary reactions. Glutathione peroxidise (GPx) is a selenocysteine - dependent enzyme. GPx in cells is the most important hydrogen peroxide (H 2 O2 ) scavenging enzyme. 
Three distinct isoforms of E-SOD have been identified in mammals, i.e. copper-zinc E-SOD (Cu/Zn-E-SOD), manganese E-SOD (Mn-E-SOD), and extracellular E-SOD; of which Cu/Zn-E-SOD and Mn-E-SOD are the major intracellular antioxidants and have generated great interest as potential targets in human carcinogenesis. Studies showed that E-SOD enzyme activity increases when the effectiveness of other enzymes decrease.  The induction of E-SOD in turn protects GPx inactivation by superoxide, resultant effect being a higher GPx activity. Considerable evidence suggests that antioxidant enzymes act to inhibit both initiation and promotion of carcinogenesis. The low activities of these enzymes play a key role in progression of lesion/condition. 
In the present study, a statistically significant decrease in E-SOD and GPx levels were observed in OSF, oral leukoplakia in comparison with the corresponding control group (P < 0.001). This finding was in accordance with studies done by Uikey et al. and Gupta et al. , Oral leukoplakia patients had slightly lower levels of E-SOD and GPx than the OSF patients; but the difference was not statistically significant (P > 0.05). Previous literature on comparison of antioxidant enzyme status between OSF and oral leukoplakia patients is scarce. Thus, this study forms an archetype; for it correlates the antioxidant enzyme status between patients with a pre-malignant condition and lesion.
Oral leukoplakia is caused due to tobacco; mainly by smoking. The sustained inhalation of ROS for a prolonged duration in the gas and tar phases of tobacco imposes an oxidative stress.  Studies by Hemalatha et al. and Khanna et al. have clearly showed the use of tobacco suppressed the production of the antioxidant enzymes, which was evident among the smokers than the non-smokers. Patel et al. showed risk of oral cancer development in habitual controls with lower antioxidant enzymes, lower oxidative stress markers, and higher lifetime tobacco exposure. Therefore, in patients having tobacco, betel quid, and other addictive habits, the equilibrium between oxidative stress and antioxidant enzyme is adversely affected. A close inter-networking between genetic susceptibility, tobacco usage, and oxidative stress can synergistically induced carcinogenesis in such patients. ,
In this study, oral cancer group showed a statistically significant (P < 0.001) decrease in levels of mean E-SOD and GPx when compared to the control group and also the lowest levels amongst the study groups. This suggests that lower antioxidant enzymes activity in oral cancer patients might be due to the depletion of the antioxidant defense system that occurs as the consequence of overwhelming free radicals by the elevated levels of lipid peroxides. GPx levels were low suggesting that most cancer cell types couldn't detoxify hydrogen peroxide.  Baskar et al., have reported altered temporal pattern in thiobarbituric acid reactive substance, which was attributed to the circadian fluctuation in antioxidant enzymes in oral cancer patients. 
| Conclusion|| |
Antioxidant enzyme levels are a subject of interest for their possible role in many cancerous conditions, are time-honored, and serve as the backbone of cellular antioxidant defense mechanism. Thus, E-SOD and GPx may be a potential biochemical index for evaluating the disease process. This study adjoins and substantiates the E-SOD and GPx levels in oral pre-cancerous lesion/condition and cancer. These antioxidant enzymes might also serve as a therapeutic targets and a guide for prognosis in patients suffering from such a malady. Further elaborate studies with larger sample size of OSF and oral leukoplakia with different clinical stages, histopathological grading, and follow-up are needed to ascertain the actual role of these biochemical parameters in the initiation and promotion of carcinogenesis.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3]