Elżbieta Skrzydlewska

ANTIOXIDANT STATUS AND LIPID PEROXIDATION IN COLORECTAL CANCER

Colon carcinogenesis is a multistep process where oxygen radicals were found to enhance carcinogenesis at all stages: initiation, promotion, and progression. Since insufficient capacity of protective antioxidant system can result in cancer, the aim of this study was to examine the activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) and the levels of reduced glutathione, vitamin C, and vitamin E. The lipid peroxidation products were also determined by measuring malondialdehyde and 4-hydroxynonenal levels in colorectal cancer tissue collected from 55 patients. In these cases the activity of superoxide dismutase, glutathione peroxidase, and glutathione reductase was significantly increased while the activity of catalase was significantly decreased in cancer tissue. However, the level of nonenzymatic antioxidant parameters (glutathione, vitamin C, and vitamin E) was significantly decreased in cancer tissue. Further lipid peroxidation was enhanced during cancer development, manifested by a significant increase in malondialdehyde and 4- hydroxynonenal levels. The obtained results indicate significant changes in antioxidant capacity of colorectal cancer tissues, which lead to enhanced action of oxygen radicals, resulting in lipid peroxidation.

Natural and synthetic antioxidants: An updated overview

Abstract The current understanding of the complex role of ROS in the organism and pathological sequelae of oxidative stress points to the necessity of comprehensive studies of antioxidant reactivities and interactions with cellular constituents. Studies of antioxidants performed within the COST B-35 action has concerned the search for new natural antioxidants, synthesis of new antioxidant compounds and evaluation and elucidation of mechanisms of action of both natural and synthetic antioxidants. Representative studies presented in the review concern antioxidant properties of various kinds of tea, the search for new antioxidants of herbal origin, modification of tocopherols and their use in combination with selenium and properties of two promising groups of synthetic antioxidants: derivatives of stobadine and derivatives of 1,4-dihydropyridine.

Effects of Amifostine on Liver Oxidative Stress Caused by Cyclophosphamide Administration to Rats

Cyclophosphamide is an inactive cytostatic, which is metabolised into active metabolites mainly in the liver. During bioactivation, reactive oxygen species (ROS) are also formed, which can modify the components of both healthy and neoplastic cells leading to decreased antioxidative capacity. Amifostine is a drug that can inactivate ROS. The aim of the present study was to evaluate the influence of amifostine on the antioxidative system of the liver of rats exposed to cyclophosphamide. Intraperitoneal administration of cyclophosphamide was found to decrease the activity of liver antioxidative enzymes, i.e. superoxide dismutase, glutathione peroxidase and glutathione reductase, and to increase catalase activity. Amifostine slightly influenced antioxidative enzyme activity, causing a significant increase only in superoxide dismutase activity. Co-administration of cyclophosphamide and amifostine nearly prevented changes in activities of superoxide dismutase, glutathione reductase and catalase, as well as to a high degree of glutathione peroxidase. Cyclophosphamide also evoked a decrease in the level of non-enzymatic antioxidants, such as reduced glutathione and vitamins C, E and A, as well as total antioxidant status. Administration of amifostine alone caused a significant increase in non-enzymatic antioxidant level that resulted in an increase in total antioxidant status. Administration of amifostine together with cyclophosphamide to a large extent prevented changes in the evaluated non-enzymatic antioxidative parameters, decreasing values of their concentration to the values of control group. Changes of liver antioxidative abilities during detoxification of cyclophosphamide were accompanied by intensified lipid peroxidation, manifested by an increase in concentration of products such as malondialdehyde and 4-hydroxynonenal. Amifostine caused the inhibition of lipid peroxidation in the liver of both control and cyclophosphamide-treated rats. In conclusion, our results suggest that amifostine significantly protects liver antioxidant properties from changes caused by cyclophosphamide treatment and in consequence prevents oxidative stress and phospholipid peroxidative damage.

Toxicological and Metabolic Consequences of Methanol Poisoning

Methanol, when introduced into all mammals, is oxidized into formaldehyde and then into formate, mainly in the liver. Such metabolism is accompanied by the formation of free radicals. In all animals, methanol oxidation, which is relatively slow, proceeds via the same intermediary stages, usually in the liver, and various metabolic systems are involved in the process, depending on the animal species. In nonprimates, methanol is oxidized by the catalase-peroxidase system, whereas in primates, the alcohol dehydrogenase system takes the main role in methanol oxidation. The first metabolite (formaldehyde is rapidly oxidized by formaldehyde dehydrogenase) is the reduced glutathione (GSH)-dependent enzyme. Generated formic acid is metabolized into carbon dioxide with the participation of H 4 folate and two enzymes, 10-formyl H 4 folate synthetase and dehydrogenase, whereas nonprimates oxidize formate efficiently. Humans and monkeys possess low hepatic H 4 folate and 10-formyl H 4 folate dehydrogenase levels and are characterized by the accumulation of formate after methanol intoxication. The consequences of methanol metabolism and toxicity distinguish the human and monkey from lower animals. Formic acid is likely to be the cause of the metabolic acidosis and ocular toxicity in humans and monkeys, which is not observed in most lower animals. Nevertheless, chemically reactive formaldehyde and free radicals may damage most of the components of the cells of all animal species, mainly proteins and lipids. The modification of cell components results in changes in their functions. Methanol intoxication provokes a decrease in the activity and concentration of antioxidant enzymatic as well as nonenzymatic parameters, causing enhanced membrane peroxidation of phospholipids. The modification of protein structure by formaldehyde as well as by free radicals results changes in their functions, especially in the activity of proteolytic enzymes and their inhibitors, which causes disturbances in the proteolytic-antiproteolytic balance toward the proteolytics and enhances the generation of free radicals. Such a situation can lead to destructive processes because components of the proteolytic-antiproteolytic system during enhanced membrane lipid peroxidation may penetrate from blood into extracellular space, and an uncontrolled proteolysis can occur. This applies particularly to extracellular matrix proteins.

Antioxidant potential of rat liver in experimental infection with Fasciola hepatica

The aim of this paper is to assess the antioxidant properties of rat liver in the course of acute and chronic fasciolosis. Wistar rats were infected per os with 30 metacercariae of Fasciola hepatica. Liver activities of antioxidant enzymes and concentrations of non-enzymatic antioxidants were determined at 4, 7, and 10 weeks post-infection. Activities of superoxide dismutase (Cu,Zn-SOD), glutathione peroxidase (GSH-Px), and glutathione reductase (GSSG-R) were decreased, catalase (CAT) activity was increased and non-enzymatic antioxidant concentrations (reduced glutathione, vitamins C, E and A) were reduced simultaneously with enhancement of lipid peroxidation processes as evidenced by increased levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Changes in the antioxidant abilities of the liver and in the phospholipid structure of the cell membrane were accompanied by rising activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as markers of liver damage.

Cyclophosphamide-induced generation of reactive oxygen species. Comparison with morphological changes in type II alveolar epithelial cells and lung capillaries

Cyclophosphamide (CP) causes lung toxicity in animals and humans. The mechanisms of pulmonary damage caused by CP are not fully understood. Possibilities include direct toxicity to pulmonary tissue or indirect toxicity through activation of pulmonary inflammatory cells. The aim of the present study was the ultrastructural analysis (in transmission electron microscope) of the changes following CP administration within the structures forming the interalveolar septum of the lungs, particularly type II epithelial cells. An attempt was also made to reveal a correlation between the morphological changes, intensity of lipid peroxidation in lung tissue homogenates and blood serum collected from the left ventricle of the heart and the alterations in the activities of superoxide dismutase (Cu, Zn-SOD) and glutathione reductase (GSSG-R). The experiment used 40 male Wistar rats of 160-180 g body weight (b.w.). The animals were divided into two groups. Group I - (20 animals) were given single intraperitoneal (i.p.) dose of 150 mg CP/1 kg b.w./1 ml PBS. Group II - (20 animals) were given single i.p. dose of 1 ml PBS. All experimental animals were sacrificed after 1 (subgroups I, II-1) and 7 (subgroups I, II-7) days of CP (or PBS) treatment. I.p. administration of CP caused an increase in lipid peroxidation products (MDA-malondialdehyde) in lung tissue homogenates especially in subgroup I-1 (p = 0.00174). No statistical differences, however, were noted in the blood serum MDA levels, although a statistically significant decrease was found in GSSG-R (p = 0.00174) and SOD (p = 0.00174) activities in the serum. The paper discusses a potential link between the findings of biochemical analysis and the morphological changes found within lung tissue. Pulmonary trombopoesis was indicated as a possible mechanism preventing a decrease in blood platelet count following CP administration.

An inter-laboratory validation of methods of lipid peroxidation measurement in UVA-treated human plasma samples

Abstract Lipid peroxidation products like malondialdehyde, 4-hydroxynonenal and F2-isoprostanes are widely used as markers of oxidative stress in vitro and in vivo. This study reports the results of a multi-laboratory validation study by COST Action B35 to assess inter-laboratory and intra-laboratory variation in the measurement of lipid peroxidation. Human plasma samples were exposed to UVA irradiation at different doses (0, 15 J, 20 J), encoded and shipped to 15 laboratories, where analyses of malondialdehyde, 4-hydroxynonenal and isoprostanes were conducted. The results demonstrate a low within-day-variation and a good correlation of results observed on two different days. However, high coefficients of variation were observed between the laboratories. Malondialdehyde determined by HPLC was found to be the most sensitive and reproducible lipid peroxidation product in plasma upon UVA treatment. It is concluded that measurement of malondialdehyde by HPLC has good analytical validity for inter-laboratory studies on lipid peroxidation in human EDTA-plasma samples, although it is acknowledged that this may not translate to biological validity.

l-Carnitine in the lipid and protein protection against ethanol-induced oxidative stress.

Chronic ethanol intoxication induces oxidative stress participating in the development of many diseases. Nutrition and the interaction of food nutrients with ethanol metabolism may modulate alcohol toxicity. One such compound is l-carnitine (l-3-hydroxy-4-N,N,N-trimethylaminobutyrate), which also reveals antioxidant abilities. The present study has been designed to investigate the effect of l-carnitine as an antioxidant on the serum and liver of rats chronically intoxicated with ethanol. Rats received l-carnitine solution (1.5g/1L) for 5 weeks and/or were treated intragastrically with ethanol for 4 weeks. In the serum and liver, the level of nonenzymatic antioxidants and lipid and protein oxidation markers were determined. It was shown that alcohol caused the increase in the level of lipid peroxidation products-conjugated dienes (by about 70% and 60% in the liver and blood serum, respectively), malondialdehyde (MDA) (by about 60% and 30% in the liver and blood serum, respectively), 4-hydroxynonenal (4-HNE) (by about 35% and 25% in the liver and blood serum, respectively), and changes in the level of protein oxidative markers-increase in dityrosine and decrease in tryptophan (by about 40%) in the serum and liver of rats. Moreover, the decrease in vitamin E level (by about 30%) and the level of glutathione (GSH) (by about 20% in the liver and blood serum) was also observed. Administration of l-carnitine to rats intoxicated with ethanol significantly protects lipids and proteins against oxidative modifications in the serum and liver. The level of conjugated dienes, MDA, and 4-HNE was decreased by about 30%, 30%, and 20% in the liver, respectively, and by about 20%, 10%, and 10% in the blood serum in comparison to the ethanol group. Moreover, the level of tryptophan was increased and dityrosine decreased by about 10% and 20% in the liver, respectively, and by about 30% and 10% in the blood serum in comparison to the ethanol group. l-carnitine partially protects nonenzymatic antioxidants against oxidative stress. The level of vitamin E was increased by about 20% and the level of GSH was increased by about 25% in the liver and blood serum in comparison to the ethanol group. It is possible that beneficial effect of l-carnitine is connected with its abilities to scavenge free radicals and to chelate metal ions.

Green Tea Protection Against Age-Dependent Ethanol-Induced Oxidative Stress

Ethanol intoxication leads to oxidative stress, which may be additionally enhanced by aging. The aim of this study was to investigate the influence of green tea as a source of water-soluble antioxidants on the ability to prevent oxidative stress in aged rats sub-chronically intoxicated with ethanol. Two-, 12-, and 24-mo-old male Wistar rats were divided into 4 experimental groups: (1) control, (2) green tea, (3) ethanol, and (4) ethanol and green tea. Ethanol intoxication produced age-dependent decrease in the activity of serum superoxide dismutase, glutathione peroxidase, and reductase and in levels of glutathione (GSH), vitamins C, E, and A, and βcarotene. Changes in the serum antioxidative ability were accompanied by enhanced oxidative modification of lipid (increase in lipid hydroperoxides, malondiadehyde, and 4-hydroxynonenal levels) and protein (rise in carbonyl group levels). Green tea partially protected against changes in antioxidant enzymatic as well as nonenzymatic parameters produced by ethanol and enhanced by aging. Administration of green tea significantly protects cellular components such as lipids and proteins against oxidative modification. Results indicate that green tea effectively protects blood serum against oxidative stress produced by ethanol as well as aging.

The role of transcription factor Nrf2 in skin cells metabolism

Skin, which is a protective layer of the body, is in constant contact with physical and chemical environmental factors. Exposure of the skin to highly adverse conditions often leads to oxidative stress. Moreover, it has been observed that skin cells are also exposed to reactive oxygen species generated during cell metabolism particularly in relation to the synthesis of melanin or the metabolism in immune system cells. However, skin cells have special features that protect them against oxidative modifications including transcription factor Nrf2, which is responsible for the transcription of the antioxidant protein genes such as antioxidant enzymes, small molecular antioxidant proteins or interleukins, and multidrug response protein. In the present study, the mechanisms of Nrf2 activation have been compared in the cells forming the various layers of the skin: keratinocytes, melanocytes, and fibroblasts. The primary mechanism of control of Nrf2 activity is its binding by cytoplasmic inhibitor Keap1, while cells have also other controlling mechanisms, such as phosphorylation of Nrf2 and modifications of its activators (e.g., Maf, IKKβ) or inhibitors (e.g., Bach1, caveolae, TGF-β). Moreover, there are a number of drugs (e.g., ketoconazole) used in the pharmacotherapy of skin diseases based on the activation of Nrf2, but they may also induce oxidative stress. Therefore, it is important to look for compounds that cause a selective activation of Nrf2 particularly natural substances such as curcumin, sulforaphane, or extracts from the broccoli leaves without side effects. These findings could be helpful in the searching for new drugs for people with vitiligo or even melanoma.