UV-B induced changes in antioxidant enzymes and their isoforms in cucumber (Cucumis sativus L.) cotyledons

To assess the role of antioxidant defense system on exposure to ultra-violet-B (UV-B) radiation, the activities of antioxidant enzymes superoxide dismutase (SOD), ascorbic acid peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (GPX), as well as the level of antioxidants ascorbic acid (AA) and alpha-tocopherol were monitored in cucumber (Cucumis sativus L. var long green) cotyledons. UV-B enhanced the activity of antioxidant enzymes as well as AA content, but decreased the level of alpha-tocopherol. Significant increase was observed in the activities of SOD and GPX. Analysis of isoforms of antioxidant enzymes by native-PAGE and activity staining revealed three isoforms of GPX in unexposed dark-grown cotyledons (control), and their intensity was enhanced by UV-B exposure. In addition, four new isoforms of GPX were observed in cotyledons after UV-B exposure. Although no new isoforms were observed for the other antioxidant enzymes, the activities of their existing isoforms were enhanced by UV-B.     

Superoxide dismutase, catalase and glutathione peroxidase activities in the brain of streptozotocin induced diabetic rats

Brain antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) levels were studied in the brains of early diabetic (72 hr) and long term diabetic (one month) rats. Diabetes was induced by injecting streptozotocin (50 mg/kg, i.p.) in citrate buffer. One group of diabetic rats was treated with insulin (1U/day/animal). The results indicate that early diabetic rats exhibit increased SOD and CAT activities with no alteration in the GPX activity. On the contrary, increased CAT decreased GPX activities with no alteration in the SOD activity, was noted in the long-term Diabetic rats. Insulin treatment reversed these alterations in both the groups. It can be concluded that, in diabetic condition antioxidant enzyme levels are elevated and insulin treatment attenuated these changes. Hence, diabetes mellitus, if left untreated, may initiate degenerative processes and other CNS complications due to accumulation of oxidative free radicals.     

Comparison between the effects of normoxia and hypoxia on antioxidant enzymes and glutathione redox state in ex vivo culture of CD34(+) cells

Hypoxia maintained biological characteristics of CD34(+) cells through keeping lower intracellular reactive oxygen specials (ROS) levels. The effects of normoxia and hypoxia on antioxidant enzymes and glutathione redox state were compared in this study. Hypoxia decreased the mRNA expression of both catalase (CAT) and glutathione peroxidase (GPX), but not affected mRNAs expression of superoxide dismutase (SOD). While the cellular GPX activities under hypoxia were apparently less than those under normoxia, neither SOD activities nor CAT activities were affected by hypoxia. The analysis of glutathione redox status and ROS products showed the lower oxidized glutathione (GSSG) levels, the higher reduced glutathione (GSH) levels, the higher GSH/GSSG ratios, and the less O(2)- and H(2)O(2) generation under hypoxia (versus normoxia). Meanwhile more primary CD34(+)CD38(-) cells were obtained when cultivation was performed under hypoxia or with N-acetyl cysteine (the precursor of GSH) under normoxia. These results demonstrated the different responses of anti-oxidative mechanism between normoxia and hypoxia. Additionally, the present study suggested that the GSH-GPX antioxidant system played an important role in HSPCs preservation by reducing peroxidation.     

镉对长江华溪蟹肝胰腺抗氧化酶活力的影响

重金属对环境的污染已成为全球面临的首要问题之一,其中镉(Cd2 )是一种广泛存在的毒性污染物,能通过消化道和呼吸道进入生物体,对机体造成损伤(Zyadah and Abdel-Baky,2000)。研究表明,Cd2 可以通过Ca2 通道穿过细胞膜进入机体(Roesijadi and Robinson,1994),诱导产生大量自由基和活性氧(ROS),从而形成氧胁迫(Toppi andGabbrielli,1994;Hegedus et al.,2001)。ROS可以与体内脂质、蛋白质和核酸反应,导致脂质过氧化、细胞膜损伤并且影响多种酶的活力,对生物体造成威胁。由于在水生生态系统中生物富集污染物的作用明显,故相对于陆地生…     

Antioxidant enzyme systems in rat liver and skeletal muscle. Influences of selenium deficiency, chronic training, and acute exercise

The influences of selenium deficiency (Se-D), chronic training, and an acute bout of exercise on hepatic and skeletal muscle antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX), as well as glutathione S-transferase (GST) and tissue lipid peroxidation, were investigated in post-weaning male Sprague-Dawley rats. Se-D per se depleted GPX in both liver and skeletal muscle but had no effect on SOD or catalase activity. One hour of treadmill running (20 m/min, 0% grade and 27 m/min, 15% grade for untrained and trained rats, respectively) significantly elevated hepatic catalase and cytosolic SOD activity; more prominent activations were found in the Se-D or untrained rats, whereas skeletal muscle antioxidant enzymes were little affected. Ten weeks of training (1 h/day, 5 days/week at 27 m/min, 15% grade) increased hepatic mitochondrial SOD by 23% (P less than 0.05) in Se-D rats. Both hepatic mitochondrial and cytosolic GPX were decreased by training whereas GPX was increased twofold in skeletal muscle mitochondria. Se-independent GPX was elevated by training only in the skeletal muscle mitochondria of Se-D rats. Lipid peroxidation (malondialdehyde formation) was increased by an acute bout of exercise in hepatic mitochondria of the untrained rats and in skeletal muscle mitochondria of the Se-D rats. These data indicate that antioxidant enzymes in liver and skeletal muscle are capable of adapting to selenium deficiency and exercise to minimize oxidative injury caused by free radicals.     

Interaction of vitamin E and exercise training on oxidative stress and antioxidant enzyme activities in rat skeletal muscles

It has been shown that free radicals are increased during intensive exercise. We hypothesized that vitamin E (vit E) deficiency, which will increase oxidative stress, would augment the training-induced adaptation of antioxidant enzymes. This study investigated the interaction effect of vit E and exercise training on oxidative stress markers and activities of antioxidant enzymes in red quadriceps and white gastrocnemius of rats in a 2x2 design. Thirty-two male rats were divided into trained vit E-adequate, trained vit E-deficient, untrained vit E-adequate, and untrained vit E-deficient groups. The two trained groups swam 6 h/day, 6 days/week for 8 weeks. The two vit E-deficient groups consumed vit E-free diet for 8 weeks. Vitamin E-training interaction effect was significant on thiobarbituric acid reactive substances (TBARSs), glutathione peroxidase (GPX), and superoxide dismutase (SOD) in both muscles. The trained vit E-deficient group showed the highest TBARS and GPX activity and the lowest SOD activity in both muscles. A significant vit E effect on glutathione reductase and catalase was present in both muscles. Glutathione reductase and catalase activities were significantly lower in the two vit E-adequate groups combined than in the two vit E-deficient groups combined in both muscles. This study shows that vit E status and exercise training have interactive effect on oxidative stress and GPX and SOD activities in rat skeletal muscles. Vitamin E deprivation augmented the exercise-induced elevation in GPX activity while inhibiting exercise-induced SOD activity, possibly through elevated oxidative stress.     

Alterations in intracellular and extracellular activities of antioxidant enzymes during suspension culture of sweetpotato

Cultured plant cells are a good system for the study of antioxidant mechanisms and for the mass production of antioxidants, because they can be grown under conditions of high oxidative stress. Alterations in the intracellular and extracellular activities of three antioxidant enzymes, superoxide dismutase (SOD), guaiacol-type peroxidase (POD), and glutathione peroxidase (GPX), were investigated in suspension cultures of sweetpotato (Ipomoea batatas) during cell growth. Intracellular SOD activities (units/mg protein) at 15 days after subculture (DAS) and 30 DAS were 10 and 20 times higher, respectively, compared with the SOD activity at 1 DAS, whereas intracellular specific POD and GPX activities did not significantly increase until after 15 DAS, when they rapidly increased. The extracellular activities of the three enzymes in culture medium were much higher than were the intracellular activities. The change in extracellular SOD activity was similar to that of extracellular GPX during cell growth. Those activities showed high levels until 5 DAS and then significantly decreased. Extracellular POD activity had an almost constant level regardless of the cell growth stage. In addition, intracellular SOD and POD isozymes were quite different from those isozymes in the culture medium. The changes in SOD and POD isozymes observed here suggest that different isozymes might modulate the levels of reactive oxygen intermediates during cell growth. Characterization of extracellular antioxidant enzymes discovered here would provide a new understanding for defense mechanism in plants.     

Cloning and mRNA expression of antioxidant enzymes in the Pacific oyster, Crassostrea gigas in response to cadmium exposure

Cadmium (Cd) is one of the most toxic heavy metal pollutants in the aquatic environment and can induce the formation of reactive oxygen species (ROS) that cause oxidative stress. In present study, we cloned catalase (CAT) and glutathione peroxidase (GPX) cDNA, and investigated its time- and dose-related effects of three Cd concentrations (0.01, 0.05 or 0.1 ppm) on mRNA levels of antioxidant enzymes (superoxide dismutase (SOD), CAT, GPX) in the gill and changes enzyme levels in the hemolymph of the Pacific oyster, Crassostrea gigas. The cDNA indentified encoded proteins of 516 and 244 amino acids corresponding to CAT and GPX, respectively. BLAST analysis from other species indicated that the residues essential to the enzymatic function of CAT and GPX proteins of C. gigas are highly conserved. Cd treatment significantly increased antioxidant enzyme mRNA expression in the gill in a time- and dose-dependent manner. The mRNA expression at 0.1 ppm Cd concentration increased up to 3 days (CAT, GPX) or 7 days (SOD) and then decreased by 7 days (CAT, GPX) or 11 days (SOD). Aspartate aminotransferase, alanine amintransferase and hydrogen peroxide (H(2)O(2)) concentrations levels increased significantly with exposure to 0.05 or 0.1 ppm Cd for 7 days. These results suggest that antioxidant enzymes play important roles in the physiological changes related to metabolism and cell protection that occur in Pacific oysters exposed to Cd.     

2-Benzoxazolinone (BOA) induced oxidative stress, lipid peroxidation and changes in some antioxidant enzyme activities in mung bean (Phaseolus aureus)

2-Benzoxazolinone (BOA), a well-known allelochemical with strong phytotoxicity, is a potential herbicidal candidate. The aim of the present study was to determine whether phytotoxicity of BOA is due to induction of oxidative stress caused by generation of reactive oxygen species (ROS) and the changes in levels of antioxidant enzymes induced in response to BOA. Effect of BOA was studied on electrolyte leakage, lipid peroxidation (LP), hydrogen peroxide (H(2)O(2)) generation, proline (PRO) accumulation, and activities of antioxidant enzymes-superoxide dismutase (SOD, 1.15.1.1), ascorbate peroxidase (APX, 1.11.1.11), guaiacol peroxidase (GPX, 1.11.1.7), catalase (CAT, 1.11.1.6) and glutathione reductase (GR, 1.6.4.2) in Phaseolus aureus (mung bean). BOA significantly enhanced malondialdehyde (MDA) content, a product of LP, in both leaves and roots of mung bean. The amount of H(2)O(2), a product of oxidative stress, and endogenous PRO increased many-fold in response to BOA. Accumulation of PRO, MDA and H(2)O(2) indicates the cellular damage in the target tissue caused by ROS generated by BOA. In response to BOA, there was a significant increase in the activities of scavenging enzymes SOD, APX, GPX, CAT, and GR in root and leaf tissue of mung bean. At 5 mM BOA, GR activity in roots showed a nearly 22-fold increase over that in control. The present study concludes that BOA induces oxidative stress in mung bean through generation of ROS and upregulation of activities of various scavenging enzymes.     

Regulatory effects of resveratrol on antioxidant enzymes: A mechanism of growth inhibition and apoptosis induction in cancer cells

Resveratrol (RSV) is a natural polyphenol that is known as a powerful chemopreventive and chemotherapeutic anticancer molecule. This study focused on the effects of RSV on the activities and expression levels of antioxidant enzymes in the cancer cells. Prostate cancer PC-3 cells, hepatic cancer HepG2 cells, breast cancer MCF-7 cells and the non-cancerous HEK293T kidney epithelial cells were treated with a wide range of RSV concentrations (10-100 μM) for 24–72 h. Cell growth was estimated by trypan blue staining, activities of the antioxidant enzymes were measured spectrophotometrically, expression levels of the antioxidant enzymes were quantified by digitalizing the protein band intensities on Western blots, and the percentage of apoptotic cells was determined by flow cytometry. Treatment with a low concentration of RSV (25 μM) significantly increased superoxide dismutase (SOD) activity in PC-3, HepG2 and MCF-7 cells, but not in HEK293T cells. Catalase (CAT) activity was increased in HepG2 cells, but no effect was found on glutathione peroxidase (GPX) upon RSV treatment. RSV-induced SOD2 expression was observed in cancer cells, although the expression of SOD1, CAT and GPX1 was unaffected. Apoptosis increased upon RSV treatment of cancer cells, especially in PC-3 and HepG2 cells. Together, our data demonstrated that RSV inhibits cancer cell growth with minimal effects on non-cancerous cells. We postulate that the disproportional up-regulation of SOD, CAT and GPX expression and enzymatic activity in cancer cells results in the mitochondrial accumulation of H₂O₂, which in turn induces cancer cell apoptosis.     

Antioxidant responses of the Mediterranean mussel, Mytilus galloprovincialis, to environmental variability of dissolved oxygen

Physiological responses of Mytilus galloprovincialis against environmental dissolved oxygen partial pressure (pO(2)) variation were studied in terms of the modulated induction of the main antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (GPX). Field in vivo studies were performed at two sites of the Lagoon of Venice, characterized by different aquatic environmental conditions implying different pO(2). SOD and GPX are more active in gills, and their complementary role is discussed. CAT is more active in the digestive gland, where the enzyme dismutates H(2)O(2) derived from divalent reduction of O(2) performed by various oxidases in peroxisomes. Antioxidant enzyme activities are correlated with water dissolved oxygen (DO), especially in the gills. This tissue, because of its anatomical localization and its physiological role, responds to DO variations modulating the induction of the antioxidant enzymes as a protection mechanism against potential toxicity due to increases in ROS formation.     

Changes in antioxidant and lignifying enzyme activities in sunflower roots (Helianthus annuus L.) stressed with copper excess

Treatment with 50 microM CuSO4 for five days caused significant decrease in dry-matter production and protein level of ten-day-old sunflower seedling roots. An increase of lipoperoxidation product rate was also observed. The involvement of some enzyme activities in the sunflower root defence against Cu-induced oxidative stress was studied. Copper treatment induced several changes in antioxidant enzymes. SOD (superoxide dismutase, EC 1.15.1.1) activity was reduced but CAT (catalase, EC 1.11.1.6) and GPX (guaiacol peroxidase, EC 1.11.1.7) activities were significantly enhanced. The lignifying peroxidase activities, assayed using coniferyl alcohol and syringaldazine, were also stimulated. Analysis by native gel electrophoresis of syringaldazine peroxidase activity showed the stimulation of an isoform (A2) and the induction of another one (A1) under cupric stress conditions. On the other hand, the activity of PAL (phenylalanine ammonia lyase, EC 4.3.1.5), which plays an important role in plant defence, was also activated. The possible mechanisms by which Cu-induced growth delay and changes in enzymatic activities involved in plant defence processes are discussed.     

Selenium-induced changes in activities of antioxidant enzymes and content of photosynthetic pigments in Spirulina platensis

Spirulina platensis exposed to various selenium （Se） concentrations （0, 10, 20, 40, 80, 150, 175, 200, 250 mg/L） accumulated high amounts of Se in a dose- and time-dependent manner. Under low Se concentrations （〈150 mg/L）, Se induced increases in biomass concentration, content of photosynthetic pigments, and activities of glutathione peroxidase （GPX）, superoxide dismutase （SOD）, catalase （CAT） and Gua-dep peroxidases （POD）, which indicates that antioxidant enzymes play an important role in protecting cells from Se stress. Higher Se concentrations （≥175 mg/L） led to higher Se accumulation and increases in activities of GPX, SOD, CAT and POD, but also induced lipid peroxidation （LPO） coupled with potassium leakage and decreases in biomass concentration and contents of photosynthetic pigment. The results indicate that increases in activities of the antioxidant enzymes were not sufficient to protect cell membranes against Se stress. Time-dependent variations in the activities of antioxidant enzymes, contents of chlorophyll a and carotenoid and the LPO level were also investigated under representative Se concentrations of 40 and 200mg/L. Opposite variation trends between SOD-CAT activities, and GPX-POD-APX activities were observed during the growth cycles. The results showed that the prevention of damage to cell membranes of S. platensis cells could be achieved by cooperative effects of SOD-CAT and GPX-POD-APX enzymes. This study concludes that S. platensis possessed tolerance to Se and could protect itself from phytotoxicity induced by Se by altering various metabolic processes.     

Methyl jasmonate-induced antioxidant defence in root apoplast from sunflower seedlings

We have investigated the physiological functions of the rapid generation of reactive oxygen species (ROS) and the implication of the antioxidant enzymes in the apoplast and symplast of roots of sunflower (Helianthus annuus L.) seedlings exposed to methyl jasmonate (MeJA, 50 μM). MeJA-elicited roots showed a fast increase in ROS content, followed by a marked increase in the activity of H₂O₂-scavenging enzymes, guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and catalase (CAT). The mechanisms responsible for MeJA-induced H₂O₂ accumulation was investigated further by studying both the production and scavenging of H₂O₂ in the extracellular matrix. Peroxidases active against (2,2′-azino-bis-[3-ethylbenzthiazoline-6-sulfonic acid], ABTS) and guaiacol were found in the apoplastic fluid, and proved to be ionically and covalently associated with sunflower cell walls, although only the peroxidase activities of the soluble apoplastic fractions and those ionically linked to the cell wall were correlated with the accumulation of the H₂O₂ detected. The results indicated that H₂O₂ accumulation is a complex and highly regulated event requiring the time-dependent stimulation and down-regulation of differently located enzymes, some of which are involved in H₂O₂ generation and degradation. It is concluded that exogenous MeJA may be involved in the oxidative stress processes by regulating antioxidant enzyme activities.     

Selenium-dependent cellular glutathione peroxidase protects mice against a pro-oxidant-induced oxidation of NADPH, NADH, lipids, and protein.

Since our prior work indicated that Se-dependent cellular glutathione peroxidase (GPX1) was necessary for protection against paraquat lethality, the present studies were to elucidate the biochemical mechanisms related to that protection. Four groups of mice [Se-deficient or -adequate GPX1 knockout and wild-type (WT)] were injected (i.p.) with 50 mg paraquat/kg body weight and tissues were collected 0, 0.5, 1, 2, 3, or 4 h after the injection. Whereas the ratios of NADPH/NADP and NADH/NAD in lung were reduced by 50-70% only 0.5 h after the injection in all groups, these two ratios in liver of the Se-adequate WT were significantly higher than those of the three GPX1 knockout or deficient groups 2-4 h after the injection. The paraquat-induced pulmonary lipid peroxidation and hepatic protein oxidation, measured as F(2)-isoprostanes and carbonyl contents, respectively, peaked at 1 h in these three groups. No such oxidative events were shown in any tissue of the Se-adequate WT throughout the time course. Whereas the F(2)-isoprostane formation was accelerated by both GPX1 knockout and Se deficiency in liver, it was not significantly elevated by the paraquat treatment in brain of any group. The paraquat injection also resulted in temporal changes in lung GPX activity and GPX1 protein in the Se-adequate WT, and significant reductions in lung total SOD activity in the GPX1 knockout or deficient groups. In conclusion, GPX1 plays a critical role in maintaining the redox status of mice under acute oxidative stress, and protects against paraquat-induced oxidative destruction of lipids and protein in vivo. These protections of GPX1 seem to be inducible and coordinated with those of other antioxidant enzymes.     

Alterations of the levels of primary antioxidant enzymes in different grades of human astrocytoma tissues

Malignant astrocytoma is the most commonly occurring brain tumour in humans. Oxidative stress is implicated in the development of cancers. Superoxide dismutase 2 (SOD2) was found to exert tumour suppressive effect in basic research, but increased SOD2 protein level was associated with higher aggressiveness of human astrocytomas. However, studies reporting alterations of antioxidant enzymes in human astrocytomas often employed less accurate methods or included different types of tumours. Here we analysed the mRNA levels, activities, and protein levels of primary antioxidant enzymes in control brain tissues and various grades of astrocytomas obtained from 40 patients. SOD1 expression, SOD1 activity, and SOD1 protein level were lower in Grade IV astrocytomas. SOD2 expression was lower in low-grade (Grades I and II) and Grade III astrocytomas than in controls, but SOD2 expression and SOD2 protein level were higher in Grade IV astrocytomas than in Grade III astrocytomas. Although there was no change in SOD2 activity and a lower activity of citrate synthase (CS), the MnSOD:CS ratio increased in Grade IV astrocytomas compared with controls and low-grade astrocytomas. Furthermore, SOD1 activity, CS activity, SOD1 expression, GPX4 expression, and GPX4 protein level were inversely correlated with the malignancy, whereas catalase activity, catalase protein, SOD2 protein level, and the SOD2:CS ratio were positively correlated with the degree of malignancy. Lower SOD2:CS ratio was associated with poor outcomes for Grade IV astrocytomas. This is the first study to quantify changes of various primary antioxidant enzymes in different grades of astrocytomas at different levels concurrently in human astrocytomas.     

Polyamine catabolism influences antioxidative defense mechanism in shoots and roots of five wheat genotypes under high temperature stress

Effect of high temperature stress on polyamine catabolism and antioxidant enzyme activity in relation to glutathione, ascorbate and proline accumulation was studied in five wheat (Triticum aestivum L.) genotypes (differently susceptible to temperature stress). High temperature significantly increased the activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR) and glutathione S-transferase (GST) in shoots of all genotypes. Higher activities of GPX in C 306, C 273 and APX in PBW 550, PBW 343 and PBW 534 demonstrate their important role in scavenging H₂O₂. Conversely, high temperature stress led to a significant decline in SOD, CAT, APX and GPX activities of roots with a subsequent increase in diamine oxidase (DAO) and polyamine oxidase (PAO) activities especially in PBW 550 and PBW 343. The concentration of ascorbic acid declined with the imposition of heat stress, however, polyamines responded to high temperature stress by increasing spermidine and spermine levels and decreasing putrescine levels. After exposure to high temperature, proline accumulation was significantly decreased in roots and increased in shoots though maximum concentration was achieved in C 306 genotype. Apparently, the wheat seedlings respond to high temperature mediated increase in reactive oxygen species (ROS) production by altering antioxidative defense mechanism and polyamine catabolism though differentially in five wheat genotypes. Among five genotypes studied, C 306 and C 273 seem to be better protected against temperature stress. The results suggested that shoots were more resistant against the destructive effects of ROS as is indicated by low levels of thiobarbituric acid reactive substances under high temperature stress.     

Gene expression evaluation of antioxidant enzymes in patients with hepatocellular carcinoma: RT-qPCR and bioinformatic analyses

Any condition leading to chronic liver disease is a potential oncogenic agent for hepatocellular carcinoma (HCC). Alterations in the expression of antioxidant enzymes could alter the redox balance. Our aim was to evaluate the expression of the genes GPX1, GPX4, SEP15, SELENOP, SOD1, SOD2, GSR, CAT, and NFE2L2 in patients with HCC. Differential gene expression analysis was performed using RNA-Seq data from the TCGA and GTEx databases, and RT-qPCR data from HCC patient samples. Bioinformatic analysis revealed significant differential expression in most genes. GPX4 expression was significantly increased (p=0.02), while SOD2 expression was significantly decreased (p=0.04) in experimental data. In TCGA samples, alpha-fetoprotein levels (mg/dL) were negatively correlated with the expression of SEP15 (p<0.001), SELENOP (p<0.001), SOD1 (p<0.001), SOD2 (p<0.001), CAT (p<0.001), and NFE2L2 (p=0.004). Alpha-fetoprotein levels were positively correlated with the expression of GPX4 (p=0.02) and SELENOP (p=0.01) in the experimental data. Low expression of GPX1 (p=0.006), GPX4 (p=0.01), SELENOP (p=0.006), SOD1 (p=0.007), CAT (p<0.001), and NFE2L2 (p<0.001), and higher levels of GSR, were associated with low overall survival at 12 months. These results suggest a significant role for these antioxidant enzymes in HCC pathogenesis and severity.