Schistosoma mansoni: melatonin enhances efficacy of cercarial and soluble worm antigens in the induction of protective immunity against infection in the hamster

Based on the beneficial influence of melatonin administration on the course of schistosomiasis and on its possible action on the immune system, we aimed in this study to establish an immunization program using Schistosoma mansoni adult worm antigen (SWAP) and cercarial antigen (CAP) alone or concurrently with melatonin treatment, for 30 successive days, in an attempt to enhance their efficacy against the infection in hamsters. Results showed that the worm reduction percentages were 53.8%, 67.01%, 56.4% and 99.3% for CAP, CAP + melatonin, SWAP, SWAP + melatonin, respectively, indicating that melatonin enhanced efficacy of SWAP but only produced a slight increase in efficacy of CAP. Highly significant reductions in egg load in the liver and alteration in the oogram pattern with a high percentage of immature eggs and few dead eggs were recorded in the groups that received melatonin treatment suggesting a possible role for melatonin in the regulation of egg production and development. On the other hand, melatonin clearly improved the oxidative status in the immunized groups. No antibody (Ab) response was recorded in the groups immunized with SWAP + melatonin while low Ab level was seen in the other melatonin-treated group. In addition to the antioxidant properties of melatonin, our results suggested that the early and continuous melatonin administration may result in immunomodulatory actions which in turn enhanced the efficacy of SWAP and CAP in different ways. This indicates the importance of further investigation of the mechanisms of melatonin action and the possible application in a vaccination program.     

Melatonin reduces oxidative damage and increases survival of mice infected with Schistosoma mansoni

The tropical parasite Schistosoma mansoni causes granulomatous inflammation after its eggs lodge in hepatic portal capillaries. In vitro studies indicate that the host's response involves the production of reactive oxygen species, although whether this occurs in vivo at the site of the infection is unknown. The role of oxidative processes in mice infected with S. mansoni was investigated in the current study using the antioxidant melatonin. In Experiment 1, the survival rate of infected mice with and without daily melatonin (10 mg/kg) administration was determined. After 56 d, 25 of 25 infected mice that were diluent treated had died. In contrast, 22 or 25 infected mice (88%) given melatonin were still alive at 56 d. Of these 22 surviving mice, melatonin injections were continued in 11 while the 11 others were switched to diluent. Within 10 d, 11 of 11 diluent-injected mice that were infected with S. mansoni were dead while 6 of 11 melatonin-treated mice survived. In Experiment 2, S. mansoni-infected mice were treated for 30 d with either melatonin or diluent. Uninfected, untreated mice served as controls. In these mice, the levels of lipid peroxidation (LPO) products, vitamin E, nitric oxide (NO), glutathione (GSH), and superoxide dismutase (SOD) activity in the liver, kidney, and spleen were measured. In the serum, cholesterol levels and liver damage (alkaline phosphatase (ALP), aspartate transaminases (AST), total protein, and albumin) were monitored. In addition, peroxynitrite anion (ONOO(-)) in the liver and kidney and inducible nitric oxide synthase (iNOS) in the spleen were immunocytochemically localized. Also, histopathological changes in the liver, kidney, and spleen were examined. The results documented increased LPO and NO levels and decreased vitamin E, GSH, and SOD activity in the liver, kidney, and spleen of S. mansoni-infected mice. Also, there was an increase in serum cholesterol and evidence of liver damage in the infected mice. Immunohistochemical results indicated positive staining of ONOO(-) in the liver and kidney and positive iNOS staining in the spleen of S. mansoni-infected mice. Histopathological observations revealed granuloma formation in the liver with eosinophil infiltration, a large number of megakaryocytes in the spleen, and degeneration with necrotic cells in some tubules of the kidney cortex in the infected mice. Melatonin administration after S. mansoni infection prevented most of the previously described changes. These results suggest that oxidative processes occur at the site of inflammation and are involved in the damaging effects of schistosomiasis and indicate that free radicals may be a major component of the disease. Likewise, melatonin, presumably due to its antioxidant and free radical scavenging activity, is highly protective against the pathological changes associated with schistosomiasis.     

Oxidative damage following cerebral ischemia depends on reperfusion - a biochemical study in rat

The extent of brain injury during reperfusion appears to depend on the experimental pattern of ischemia/reperfusion. The goals of this study were: first, to identify the rate of free radicals generation and the antioxidant activity during ischemia and reperfusion by means of biochemical measurement of lipid peroxidation (LPO) and both enzymatic (superoxid dismutase - SOD, catalase - CAT, glutathion peroxidase - GPx) and non-enzymatic antioxidants activity (glutathione - GSH); and second, to try to find out how the pattern of reperfusion may influence the balance between free radical production and clearance. Wistar male rats were subject of four-vessel occlusion model (Pulsinelly & Brierley) cerebral blood flow being controlled by means of two atraumatic arterial microclamps placed on carotid arteries. The level of free radicals and the antioxidant activity were measured in ischemic rat brain tissue homogenate using spectrophotometrical techniques. All groups subjected to ischemia shown an increase of LPO and a reduction of the activity of enzymatic antioxidative systems (CAT, GPx, SOD) and non-enzymatic systems (GSH). For both groups subjected to ischemia and reperfusion, results shown an important increase of LPO but less significant than the levels found in the group with ischemia only. Statistically relevant differences (p<0.01) between continuous reperfusion and fragmented reperfusion were observed concerning the LPO, CAT, SOD and GSH levels, oxidative aggresion during fragmented reperfusion being more important.     

The effects of selenium on oxidative stress biomarkers in the freshwater characid fish matrinxã, Brycon cephalus (Günther, 1869) exposed to organophosphate insecticide Folisuper 600 BR (methyl parathion)

Methyl parathion (MP), an organophosphate widely applied in agriculture and aquaculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The antioxidant roles of selenium (Se) were evaluated in Brycon cephalus exposed to 2 mg L(-1) of Folisuper 600 BR (MP commercial formulation - MPc, 600 g L(-1)) for 96 h. Catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) levels in the gills, white muscle and liver were evaluated in fish fed on diets containing 0 or 1.5 mg Se kg(-1) for 8 weeks. In fish treated with a Se-free diet, the MPc exposure increased SOD and CAT activities in all tissues. However, the GPx activity decreased in white muscle and gills whereas no alterations were observed in the liver. MPc also increased GST activity in all tissues with a concurrent decrease in GSH levels. LPO values increased in white muscle and gills and did not change in liver after MPc exposure. A Se-supplemented diet reversed these findings, preventing increases in LPO levels and concurrent decreases in GPx activity in gills and white muscle. Similarly, GSH levels were maintained in all tissue after MPc exposure. These results suggest that dietary Se supplementation protects cells against MPc-induced oxidative stress.     

The effects of dietary boric acid and borax supplementation on lipid peroxidation,antioxidant activity,and DNA damage in rats

The aims of this study were to clarify the effects of high dietary supplementation with boric acid and borax, called boron (B) compounds, on lipid peroxidation (LPO), antioxidant activity, some vitamin levels, and DNA damage in rats. Thirty Sprague Dawley male rats were divided into three equal groups: the animals in the first group (control) were fed with a standard rodent diet containing 6.4 mg B/kg, and the animals in the experimental group were fed with a standard rodent diet added with a supra-nutritional amount of boric acid and borax (100 mg B/kg) throughout the experimental period of 28 days. The B compounds decreased malondialdehyde (MDA), DNA damage, the protein carbonyl content (PCO) level in blood, and glutathione (GSH) concentration in the liver, Cu–Zn superoxide dismutase (SOD), and catalase (CAT) activity in the kidney. The B compounds increased GSH concentration in blood and the vitamin C level in plasma. Consequently, our results demonstrate that B supplementation (100 mg/kg) in diet decreases LPO, and enhances the antioxidant defense mechanism and vitamin status. There are no differences in oxidant/antioxidant balance and biochemical parameters except for serum vitamin A and liver GSH concentration, between the boron compounds used in this study.     

Comparison of the protective effect of melatonin with other antioxidants in the hamster kidney model of estradiol-induced DNA damage

17beta-Estradiol (E(2)) is a known carcinogen. Estrogen induction of tumors in hamster kidney is a model of estrogen-related carcinogenesis. Melatonin is a well-known antioxidant, free radical scavenger and oncostatic agent. Changes in the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), an index of DNA damage, were measured in kidneys, liver and testes from hamsters treated with E(2) (75mg/kg b.w.) and collected 5h later. Potential protective effects of melatonin, N-acetylserotonin (NAS), indole-3-propionic acid (IPA) and ascorbic acid (AA) against E(2)-induced DNA damage were tested. The antioxidants were applied in equimolar doses of 64.5 micromol/kg b.w., 2 and 0.5h before and 2 and 4h after E(2) treatment. E(2) treatment caused a significant increase in 8-oxodGuo levels in kidneys, but did not influence significantly the oxidation of guanine bases in liver and testes. Melatonin, IPA and AA, but not NAS, completely prevented E(2)-induced DNA damage in hamster kidneys. It is concluded that melatonin, IPA and AA may be effective in protecting against E(2)-related DNA damage and, consequently, carcinogenesis.     

Fenugreek seeds modulate 1,2-dimethylhydrazine-induced hepatic oxidative stress during colon carcinogenesis

1,2-dimethylhydrazine (DMH) is a colon carcinogen which undergoes oxidative metabolism in the liver. We have investigated the modulatory effect of fenugreek seeds (a spice) on colon tumor incidence as well as hepatic lipid peroxidation (LPO) and antioxidant status during DMH-induced colon carcinogenesis in male Wistar rats. In DMH treated rats, 100% colon tumor incidence was accompanied by enhanced LPO and a decrease in reduced glutathione (GSH) content as well as a fall in glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activities. Inclusion of fenugreek seed powder in the diet of DMH treated rats reduced the colon tumor incidence to 16.6%, decreased the LPO and increased the activities of GPx, GST, SOD and CAT in the liver. We report that fenugreek modulates DMH-induced hepatic oxidative stressduring colon cancer     

Vitamin D and melatonin protect the cell’s viability and ameliorate the CCl4 induced cytotoxicity in HepG2 and Hep3B hepatoma cell lines

Carbon tetrachloride (CCl₄) is widely used to induce liver toxicity in in vitro/in vivo models. Lipid peroxidation (LPO) begins with toxicity and affects cell viability. Recently, the beneficial effects of melatonin and Vitamin D on cell proliferation in human normal and cancer cells were found. This study was planned to evaluate antioxidant and cytoprotective activity of melatonin and Vitamin D in CCl₄ induced cytotoxicity in HepG2 and Hep3B hepatoma cell lines. Based on the cytotoxicity assay, melatonin and Vitamin D were evaluated for cytotoprotective potential against CCl₄ induced toxicity in HepG2 and Hep3B liver cell lines by monitoring cell viability, LPO and glutathione (GSH) level. Different dosages of CCl₄ (0.1, 0.2, 0.3 and 0.4 % v/v) were applied to HepG2 and Hep3B cells in order to determine the most toxic dosage of it in a time dependent manner. The same experiments were repeated with exogenously applied melatonin (MEL) and Vitamin D to groups treated with/without CCL₄. Cell viability was determined with MTT measurements at the 2nd, 24th and 48th h. GSH content and Malondialdehyde levels were measured from the cell lysates. As a result, both melatonin and Vitamin D administration during CCl₄ exposure protected liver cells from CCl₄ induced cell damage. Increase in LPO and decrease in GSH were found in the CCl₄ groups of both cells. Contrary to these results administration of MEL and Vitamin D on cells exhibited results similar to the control groups. Therefore, melatonin and Vitamin D might be a promising therapeutic agent in several toxic hepatic diseases.     

Effects of fluoride on hepatic antioxidant system and transcription of Cu/Zn SOD gene in young pigs

Thirty-two barrows (Duroc x Landrace x Yorkshire) were randomly divided into four groups, each of which included eight pigs. The groups received the same basal diet supplemented with 0, 100, 250 and 400mg/kg fluoride, respectively. The malondialdehyde (MDA) and glutathione (GSH) levels, antioxidant enzymes activities and zinc/copper superoxide dismutase (Cu/Zn SOD) mRNA content in the liver were determined to evaluate the fluoride hepatic intoxication. Results showed the increased lipid peroxides (LPO) level and the reduced GSH content, along with a concomitant decrease in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px). Moreover, the level of hepatic Cu/Zn SOD mRNA was also significantly reduced. We suggest the mechanism of fluoride injuring the liver as follows: fluoride causes a decrease in Cu/Zn SOD mRNA and the reduced activities of antioxidant enzymes, leads to the declined ability of scavenging free radicals with excessive production of LPO, which seriously damages the hepatic structure and function.     

Changes in the amount of reduced glutathione and activity of antioxidant enzymes in chosen mouse organs influenced by zymosan and melatonin administration

Reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) are vital components of the antioxidative barrier in animal cells. It is suggested more often now that the effectiveness of the protection of cells against the oxidative stress caused by the inflammation process depends on the amount of GSH and the activity of SOD, CAT and GSHPx. That is why the effect of zymosan A (40 mg/kg body mass) and the combined treatment with zymosan A (at the same dose) and melatonin (50 mg/kg body mass) on the amount of GSH in the blood and the amount of GSH and activity of SOD, CAT and GSHPx in the brain, liver and kidneys of male mice was estimated. Animals (n = 108) were decapitated after 3, 6 and 24 hours since the moment of the administration of only zymosan A, and combined zymosan A and after one hour melatonin. After the injection of zymosan A it was found that the amount of GSH is significantly lower after 3 and 6 hours in the blood and studied organs. The administration of zymosan A, followed by the administration of melatonin limited the decrease in the amount of this tripeptide in the same time. Simultaneously, the decrease in the amount of GSH in the studied organs was accompanied by a similar decrease in the activity of SOD, CAT and GSHPx after the injection of only zymosan A and a limited decrease in the activity after the administration of both zymosan A and melatonin. It is suggested that a decreased content of GSH and a decrease in the activity of the studied antioxidative enzymes is caused by the oxidative stress accompanying the inflammation process.     

Accumulation and oxidative stress biomarkers in Japanese flounder larvae and juveniles under chronic cadmium exposure

This study investigated how Cd exposure affected oxidative biomarkers in Japanese flounder, Paralichthys olivaceus, at early life stages (ELS). Fish were exposed to waterborne Cd (0–48 µg L^− 1) from embryonic to juvenile stages for 80 days. Growth, Cd accumulation, activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione S-transferase (GST, EC 2.5.1.18), and levels of glutathione (GSH) and lipid peroxidation (LPO) were investigated at three developmental stages. Flounder growth decreased and Cd accumulation increased with increasing Cd concentration. In metamorphosing larvae, CAT and SOD activities were inhibited and GSH level was elevated, while LPO was enhanced by increasing Cd concentrations. CAT and GST activities of settling larvae were inhibited but GSH level was elevated at high Cd concentrations. In juveniles, SOD activity and LPO level were increased but GST activity was inhibited as Cd concentration increased. Antioxidants in flounder at ELS were able to develop ductile responses to defend against oxidative stress, but LPO fatally occurred due to Cd exposure. These biochemical parameters could be used as effective oxidative biomarkers for evaluating Cd contamination and toxicity in marine environments: CAT, SOD, GSH, and LPO for metamorphosing stage; CAT, GSH, and GST for settling stage; and SOD, GST, and LPO for juvenile stage.     

Prophylactic effect of melatonin in reducing lead-induced neurotoxicity in the rat

Oxidative stress is a likely molecular mechanism in lead neurotoxicity. Considering the antioxidant properties of melatonin, this study investigated the neuroprotective potential of melatonin in the hippocampus and corpus striatum of rats treated with lead. Three groups of male rats (control, lead acetate-treated [100 mg/kg], and lead acetate plus melatonin [10 mg/kg] for 21 consecutive days) were used. Levels of products of lipid peroxidation (LPO), glutathione (GSH) and superoxide dismutase (SOD) activity were measured in brain homogenates. Histological changes in the pyramidal cells of the hippocampus and the putamen of the corpus striatum were examined. The results documented increased LPO and decreased GSH and SOD activity in the brain homogenates of lead-treated rats. Histological observations revealed severe damage and a reduction in neuronal density in the hippocampus and corpus striatum. When melatonin was given to lead-treated rats, it almost completely attenuated the increase in LPO products and restored GSH levels and SOD activity. Also, the morphological damage was reduced and neuronal density was restored by melatonin. Considering the ease with which melatonin enters the brain, these results, along with previous observations, suggest that melatonin may be useful in combating free radical-induced neuronal injury that is a result of lead toxicity.     

Ameliorative action of melatonin on oxidative damage induced by atrazine toxicity in rat erythrocytes

Excessive generation of reactive oxygen species (ROS) can induce oxidative damage to vital cellular molecules and structures including DNA, lipids, proteins, and membranes. Recently, melatonin has attracted attention because of their free radical scavenging and antioxidant properties. The aim of this study was to evaluate the possible protective role of melatonin against atrazine-induced oxidative stress in rat erythrocytes in vivo. Adult male albino rats of Wistar strain were randomly divided into four groups. Control group received isotonic saline; melatonin (10 mg/kg bw/day) group; atrazine (300 mg/kg of bw/day) group; atrazine + melatonin group. Oral administration of atrazine and melatonin was given daily for 21 days. Oxidative stress was assessed by determining the glutathione (GSH) and malondialdehyde (MDA) level, and alteration in antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione-S-transferase (GST), and glucose-6-phosphate dehydrogenase (G-6-PD) in the erythrocytes of normal and experimental animals. A significant increase in the MDA levels and decrease in the GSH was observed in the atrazine treated animals (P < 0.05). Also, significant increase in the activities of SOD, CAT, GPx, and GST were observed in atrazine treated group compared to controls (P < 0.05). Moreover, significant decrease in protein, total lipids, cholesterol, and phospholipid content in erythrocyte membrane were demonstrated in atrazine treated rats. Administration of atrazine significantly inhibits the activities of G-6-PD and membrane ATPases such as Na(+)/K(+)-ATPase, Mg(2+)-ATPase, and Ca(2+)-ATPase (P < 0.05). Scanning electron microscopic (SEM) examination of erythrocytes revealed morphological alterations in the erythrocytes of atrazine treated rats. Furthermore, supplementation of melatonin significantly modulates the atrazine-induced changes in LPO level, total lipids, total ATPases, GSH, and antioxidant enzymes in erythrocytes. In conclusion, the increase in oxidative stress markers and the concomitant alterations in antioxidant defense system indicate the role of oxidative stress in erythrocytes of atrazine-induced damage. Moreover, melatonin shows a protective role against atrazine-induced oxidative damage in rat erythrocytes.     

Cathepsin B differential expression and enzyme processing and activity during Fundulus heteroclitus embryogenesis

The present study aimed to test the effects of melatonin on oxidative stress in the yellowtail clownfish, Amphiprion clarkii, as produced by light emitting diodes (LEDs): red, green, and blue. We investigated the effects of the different LEDs on oxidative stress by measuring the mRNA expression of arylalkylamine N-acetyltransferase (AANAT2), the expression and activities of antioxidant enzymes (superoxide dismutase, SOD (EC 1.15.1.1); and catalase, CAT (EC 1.11.1.6)), and plasma H2O2 and plasma melatonin levels. In red light, the expression of AANAT2, SOD, and CAT mRNA was significantly higher than those under the other light spectra. SOD and CAT activities and plasma H2O2 and melatonin levels were also significantly higher for the red spectra than those for the other light spectra. These results indicate that red light induces oxidative stress. To investigate the effects of melatonin on oxidative stress, we injected melatonin into live fish (in vivo) or treated cultured pineal organ (in vitro) with melatonin. We found that AANAT2, SOD, and CAT mRNA expression levels, SOD and CAT activities, and plasma H2O2, lipid peroxidation (LPO) and melatonin levels were significantly lower than those for the controls. Therefore, our results indicate that red light induces oxidative stress and melatonin plays the role of a strong antioxidant in yellowtail clownfish.     

Antioxidant response and oxidative stress levels in Macrobrachium borellii (Crustacea: Palaemonidae) exposed to the water-soluble fraction of petroleum

The aim of the present work was to evaluate the effect of the water soluble fraction of hydrocarbons (WSF) on the antioxidant status of the freshwater prawn Macrobrachium borellii. First, seasonal variations were studied in a non-polluted area. Hepatopancreas and gills showed season-related fluctuations in catalase (CAT), glutathione-S-transferase (GST) activities and in lipid peroxidation levels (LPO), but not in superoxide dismutase (SOD). Then, adults were exposed semi-statically to sublethal doses for 7days. CAT, SOD, GST, and glutathione peroxidase (GPx) activities and LPO, reduced glutathione (GSH) and protein oxidation (PO) levels were determined. Exposed individuals showed significant increases in CAT, SOD, and GST activities in hepatopancreas and CAT activity in gills. GPx activity did not vary in either tissues. While LPO levels increased, GSH levels decreased significantly in hepatopancreas of exposed animals, but PO levels showed no variation. Induction of SOD was also assessed by Real-time PCR mRNA expression in hepatopancreas. The non-enzymatic antioxidant activity was also tested; ABTS 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) was higher in hemolymph of treated-prawns compared to controls, but ferric reducing activity of plasma assay (FRAP) values did not change. Taken together, the present results indicated that the antioxidant defenses of M. borellii, mainly in hepatopancreas, were significantly affected by aquatic hydrocarbon contamination, regardless of the season.     

Melatonin and vitamin C administration ameliorate diazepam-induced oxidative stress and cell proliferation in the liver of rats

Abstract.  Objective : Oxidative stress is a likely molecular mechanism in long-term diazepam administration. The benefits of antioxidants (melatonin and vitamin C) against diazepam-induced cell proliferation, DNA synthesis and oxidative damage were investigated in this study. Materials & methods : Four equal-sized groups of male rats [control, diazepam (3 mg/kg), diazepam plus melatonin (5 mg/kg) and diazepam plus vitamin C (50 mg/kg)] were used. Levels of lipid peroxides (LPO), superoxide dismutase (SOD) activity and glutathione (GSH) concentration were measured in tissue homogenates. Cell proliferation and rate of DNA synthesis were detected by autoradiography. Results : Results documented increased labelling index, ³H-thymidine incorporation (DNA synthesis), LPO plus decrease in GSH levels and SOD activity in livers of diazepam-administered rats versus those of controls. When melatonin and vitamin C were given to diazepam-administered rats, they almost attenuated the increase of labelling index, DNA synthesis and LPO, and restored the levels of GSH and SOD activity. Conclusion : These results suggest long-term hazard in use of drugs such as diazepam; they may be toxic and damage terminates in complex liver damage. Furthermore, melatonin and vitamin C may be useful in combating free radical-induced liver injury resulting from hazard and/or repeated diazepam administration.     

Oxidative stress and genotoxic effects in gill and kidney of Anguilla anguilla L. exposed to chromium with or without pre-exposure to beta-naphthoflavone

Fish in the aquatic environment can be subjected to a multipollution state and the occurrence of sequential exposures is an important aspect of eco-toxicological research. In this context, a preceding exposure can affect a toxic response to a subsequent exposure. Therefore, the current study was based on sequential exposures, viz. to a PAH-like compound (beta-naphthoflavone, BNF) followed by a heavy metal (chromium, Cr), focusing on the assessment of oxidative stress responses and their role in induction of genotoxicity. Oxidative stress responses in gill and kidney were investigated in European eel (Anguilla anguilla L.), and measured as lipid peroxidation (LPO), glutathione peroxidase (GPX), catalase (CAT) and glutathione S-transferase (GST) activity, and reduced glutathione (GSH) concentration, whereas genotoxicity was measured as DNA strand breakage. Fish were exposed for 24 h to two Cr concentrations (100 microM, 1 mM), with or without pre-exposure to BNF (2.7 microM, 24 h). In gill, a GSH decrease was observed along with loss of DNA integrity at all exposure conditions except at the lowest Cr concentration, showing a crucial role of GSH over genotoxicity. Moreover, sporadic induction of antioxidant enzymes was not effective in the protection against genotoxicity. However, a different mechanism seems to occur in kidney, since the loss of DNA integrity detected for all exposed groups was not accompanied by alterations in antioxidant levels. With regards to peroxidative damage, both organs showed an LPO increase after sequential exposure to BNF and 100 microM Cr. However, no association between LPO induction and antioxidant responses could be established, showing that LPO is not predictable solely on the basis of antioxidant depletion. The interference of BNF pre-exposure with the response of organs to Cr showed a marked dependence on the Cr concentration. Gill showed synergistic effects on LPO and GPX increase, as well as on CAT and GSH decrease for the lowest Cr concentration. However, for the highest concentration an additive effect on decrease of DNA integrity and an antagonistic effect on the increase of GPX were observed. In kidney, synergistic effects were evident on LPO increase and GSH decrease for the lowest Cr concentration, as well as on CAT and GST decrease for the highest concentration. In contrast, an antagonistic action was observed on DNA integrity loss for both Cr concentrations. The current results are relevant in assessing the interactions of PAHs and metals and contribute to a better knowledge about oxidative stress and mechanisms of genotoxicity in fish.     

Melatonin reduces oxidative stress induced by ochratoxin A in rat liver and kidney

Melatonin (MEL) displays antioxidant and free radical scavenger properties. In the present study, the effect of MEL on the oxidative stress induced by ochratoxin A (OTA) administration in rats was investigated. Four groups of 15 rats each were used: controls, MEL-treated rats (5 mg/kg body mass), OTA-treated rats (250 μg/kg) and MEL+OTA-treated rats. After 4 weeks of treatment, the levels of malondialdehyde (MDA), a lipid peroxidation product (LPO) were measured in serum and homogenates of liver and kidney. Also, the levels of glutathione (GSH), and activities of glutathione reductase (GR), glutathione peroxidase (GSPx), superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) in liver and kidney were determined. In OTA-treated rats, the levels of LPO in serum and in both liver and kidney were significantly increased compared to levels in controls. Concomitantly, the levels of GSH and enzyme activities of SOD, CAT, GSPx and GR in both liver and kidney were significantly decreased in comparison with controls. In rats received MEL+OTA, the changes in the levels of LPO in serum and in liver and kidney were not statistically significant compared to controls. Concomitantly, the levels of GSPx, GR and GST activities in both liver and kidney tissues were significantly increased in comparison with controls. Similar increases in GSPx, GR and GST activities were also observed in MEL-treated rats when compared with controls. In conclusion, the oxidative stress may be a major mechanism for the toxicity of OTA. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and stimulation of GST activities. Thus, clinical application of melatonin as therapy should be considered in cases of ochratoxicosis.     

Protein kinase A phosphorylation of the multifunctional protein CAD antagonizes activation by the MAP kinase cascade

Aβ vaccination as a therapeutic intervention of Alzheimer’s has many challenges, key among them is the regulation of inflammatory processes concomitant with excessive generation of free radicals seen during such interventions. Here we report the beneficial effects of melatonin on inflammation associated with Aβ vaccination in the central and peripheral nervous system of mice. Mice were divided into three groups (n = 8 in each): control, inflammation (IA), and melatonin-treated (IAM). The brain, liver, and spleen samples were collected after 5 days for quantitative assessment of plasma lipid peroxides (LPO), an oxidative stress marker, and antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (Gpx). IA group mice have shown the elevated concentration of LPO significantly while there was a reduction at antioxidant enzyme levels. In addition, a significant (P < 0.05) reduction in neurotransmitters like dopamine (DA), 5-hydroxytryptamine (5-HT), and norepinephrine (NE) was also observed in the IA group mice. Nevertheless, their metabolites, such as homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) increased significantly (P < 0.05) as compared to control. Samples were further evaluated at microscopic level to examine the neuropathological changes by immunohistochemical methods. Melatonin treatment effectively reversed these above changes and normalized the LPO and antioxidant enzyme levels (P < 0.05). Furthermore, melatonin salvaged the brain cells from inflammation. Our Immunohistochemical findings in the samples of melatonin-treated animals (IAM group) indicated diminished expression of glial fibrillary acidic protein (GFAP) and nuclear factor kappa B (NfκB) than those observed in the IA group samples. Our results suggest that administration of melatonin protects inflammation associated with Aβ vaccination, through its direct and indirect actions and it can be an effective adjuvant in the development of vaccination in immunotherapy for Alzheimer’s disease (AD).     

Bacopa monniera Linn. extract modulates antioxidant and marker enzyme status in fibrosarcoma bearing rats

Antioxidative property and tumor inhibitive property of B. monniera (20mg/kg body wt, sc) was examined in 3-methylcholanthrene induced fibrosarcoma rats. Antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the levels of glutathione (GSH) and the rate of lipid peroxidation (LPO) in the liver and kidney tissues were assessed. A significant increase was noted for the rate of LPO with a corresponding decrease in the antioxidant enzyme status in fibrosarcoma bearing rats. In fibrosarcoma bearing rats, the tumor markers like lactate dehydrogenase (LDH), creatine kinase (CK), alanine transaminase (ALT), aspartate transaminase (AST) and sialic acid (SA) were increased in the serum. Treatment with B. monniera extract significantly increased the antioxidant enzyme status, inhibited lipid peroxidation and reduced the tumor markers. It can be concluded that B.monniera extract promotes the antioxidant status, reduces the rate of lipid peroxidation and the markers of tumor progression in the fibrosarcoma bearing rats.