Induction Of Glutathione S-transferase Activity Research Articles

Oxidative stress and histological changes caused by lambda-cyhalothrin on the snail Helix aspersa

This study was interested in evaluating the toxicity of an insecticide based on lambda-cyhalothrin, newly approved and widely used in agriculture in Algeria, on an alternativebiological model, the snail Helix aspersa.In order to achieve these objectives, we based our-selves on the evaluation of the degree of oxidative stress by monitoring the average weightof the snails, the level of total proteins and Glutathione-SH (GSH), as well as the enzymaticactivities of Glutathione S-transferase (GST ) and Catalase activity (CAT ) at the level ofthe hepatopancreas. We performed a histopathological examination of the kidney and hep-atopancreas.The results show that lambda-cyhalothrin causes a dose-dependent decreasein the average weight of snails, an increase in the content of total proteins, and a decrease inthe level of GSH , in parallel with the induction of GST activities and CAT. Histopathologicalexamination conirmed the toxicity of lambda-cyhalothrin in Helix aspersa.

The neonicotinoid insecticide imidacloprid, but not salinity, impacts the immune system of Sydney rock oyster, Saccostrea glomerata

The broad utilisation of neonicotinoids, particularly imidacloprid (IMI), in agriculture has led to unplanned contamination of aquatic systems around the world. The sublethal effects of individual pesticides on the immune system of oysters, as well as their combined effects with other environmental stressors that fluctuate in estuarine environments, such as salinity, are yet to be investigated in ecotoxicology. We investigated the acute (4 d) toxicity of IMI in two salinity regimes on the immune parameters of Sydney rock oysters (SRO), including total hemocyte counts (THC), differential hemocyte counts (DHC), phagocytosis and hemocyte aggregation (HA), hemolymph protein expression and enzyme (catalase (CAT), glutathione S-transferase (GST) and acetylcholinesterase (AChE)) activities. Environmentally relevant concentrations of IMI were found to cause an increase in THC, induce GST activity, reduce HA, and inhibit AChE activity. However, DHC, CAT activity and phagocytosis were not significantly impacted at any test concentration at either salinity. IMI concentrations ≥0.01 mg/L significantly altered the expression of 28 proteins in the hemolymph of SRO, including an increase in the relative expression of extracellular superoxide dismutase, severin, ATP synthase subunit beta, as well as stress response proteins (heat shock proteins, serine/threonine-protein kinase DCLK3 and peroxiredoxin-1), and a decrease/absence of collagen alpha-4 (VI) and alpha-6 (VI) chain, metalloendopeptidase, L-ascorbate oxidase, transporter, CEP209_CC5 domain-containing protein and actin. This study indicates that the immune system of SRO can be impacted at environmentally relevant concentrations of IMI, but reduced salinity does not appear to influence the toxicity of this insecticide.

Target-site and non-target-site-based resistance to tribenuron-methyl in multiply-resistant Myosoton aquaticum L.

Myosoton aquaticum L., a widespread and competitive winter weed of wheat in China, has evolved resistance to many classes of herbicides. In one M. aquaticum population (AH03), collected from Anhui Province, where tribenuron-methyl and florasulam had been used to control this weed resistance to both herbicides had evolved. Compared with the sensitive population, HN03(S), the resistant (R) population, AH03, was highly resistant to tribenuron-methyl, flucarbazone-Na and pyroxsulam, moderately resistant to pyrithiobac‑sodium, and florasulam, and had low resistance to diflufenican. AH03 was still controlled by imazethapyr, 2,4-D butylate, fluroxypyr-meptyl, and isoproturon. Pretreatment with the P450 inhibitor malathion reduced the GR50 value of tribenuron-methyl by 43% in the R population, and by 25% in the S population. This indicates that P450-mediated enhanced metabolism is one likely mechanism for tribenuron-methyl resistance in M. aquaticum. Glutathione-S-transferase (GST) activity could be induced by tribenuron-methyl in both the R and S populations. However, both the basal and induced GST activity of the R population was lower than that of the S population. The in vitro ALS assay confirmed that the ALS from the R plants showed a high resistance (52.93-fold) to tribenuron-methyl. ALS gene sequencing revealed a Pro197Ala substitution in the R plants. Based on the ALS gene sequence analysis, molecular markers were also developed to identify the specific Pro197Ala mutation. This population of M. aquaticum has multiple resistance and target-site (ALS Pro197Ala) and non-target-site resistance mechanisms contribute to tribenuron-methyl resistance.

Induction of oxidative stress by chlorothalonil in the estuarine polychaete Laeonereis acuta

Chlorothalonil is an active biocide applied in antifouling paints, and also used as fungicide in agricultural activities with the purpose to protect plants from foliar and seed diseases. Thus, the aim of this study was to evaluate the effects of chlorothalonil exposure on biochemical biomarkers of oxidative metabolism as well as on cholinesterases in the estuarine polychaete Laeonereis acuta. Animals were exposed for 24 and 96 h to the following nominal concentrations of chlorothalonil: 0.1, 10.0 and 100.0 μg/L. The antioxidant capacity against peroxyl radicals (ACAP) and the activity of the enzymes catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutamate cysteine ligase (GCL), acetylcholinesterase (AChE) and propionylcholinesterase (PChE) were evaluated in whole-body tissue. In addition, the levels of reduced glutathione (GSH), lipid peroxidation (LPO), glycogen and lactate levels were also analyzed. A reduction in ACAP levels was observed in animals exposed to the higher chlorothalonil concentration, concomitantly with an induction of GST activity as well as diminution in GSH content in these animals. This disturbance in the redox state of animal tissues leads to an oxidative stress situation, resulting in an induction in LPO levels. It was also demonstrated that chlorothalonil exposure causes alteration in AChE activity, possibly related to damage to membrane lipids. These results demonstrated that chlorothalonil possesses harmful effects to estuarine animals and its use as antifouling biocide has to be carefully reconsidered in risk analysis studies.

Cancer preventive effects of a specific probiotic fermented milk containing Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2 on male F344 rats treated with 1,2-dimethylhydrazine

The effect of fermented milk (FM) consisting of three probiotic strains (Lactobacillus acidophilus CL1285, L. casei LBC80R and L. rhamnosus CLR2) on colon cancer prevention in rats treated with dimethylhydrazine (DMH) was investigated. The rats were divided into 7 groups of 8 animals. Rats were fed with a high fat low fibre diet; group 1 was a negative control, while groups 2 to 7 were injected with DMH (30 mg/kg s.c.) once a week for six weeks. Groups 3 to 7 were gavaged respectively with 2, 1.5, 1, 0.5 and 0.25 ml of FM every day. After 12 weeks, the rats were sacrificed and the colon, caecum and liver were collected. Aberrant crypt foci (ACF) in the colon were determined using a microscope. Detoxifying enzymes like quinone reductase (QR) and glutathione-S-transferase (GST) and faecal enzymes such as β-glucosidase and β-glucuronidase were evaluated by spectrophotometry. The rats fed with the three highest doses significantly lowered aberrant crypt (AC) count, while those supplemented with 1.5 and 2 ml FM lowered significantly ACF count compared to group 2 (p ≤ 0.05). Rats fed with the highest doses significantly induced GST activity, while only rats fed with 2 ml reduced significantly β-glucuronidase activity compared to group 2 (p ≤ 0.05). These results indicate that the FM could have a potential role in colorectal cancer prevention.

Ripening of cheddar cheese with Lactobacillus helveticus as adjunct culture produces peptides that protect human vein endothelial cells against inflammatory markers relevant to cardiovascular disease (1034.12)

Lactobacillus helveticus has been recognized as an adjunct culture that contributes to flavor development in cheddar cheese. However changes in peptides profiles throughout ripening and their anti‐inflammatory effects on HUVEC have not been investigated.Peptides in cheddar cheese (Cougar Gold) were assessed by LC‐MS/MS analysis throughout ripening (0, 6, and 12 months). The protective effects of peptides in HUVEC challenged with glucose (G) or E. coli lipopolysaccharides (LPS) were assessed by quantification of reactive oxygen species (ROS), H2O2, glutathione S‐transferase activity (GST), and expression of inflammatory genes by standard analytical methods.Results showed that peptides produced within 0‐12 months ripening varied in masses from 1226 to 7474 Da with the lowest masses found at 12 months. These peptides prevented ROS production in HUVEC challenged with LPS or G to 0.7‐fold and to 0.36‐fold of LPS‐ and G‐controls, respectively and this was correlated with levels of H2O2. These effects were in part due to higher induction of GST by the 12 month peptides (1.64‐fold of control) and downregulation of NF‐ĸB mRNA and NF‐ĸB‐target genes IL‐8, IL‐6, IL‐1β, and ICAM1. We are currently investigating the peptide profiles and bioavailability throughout ripening. Overall, these results strongly suggest that these peptides can protect HUVEC against inflammation and the mechanisms involve more than the widely reported antihypertensive activities with relevance for CVD prevention.

Response of glutathione conjugation system to soil borneRhizoctoniainfection of okra

Okra seedlings tolerated soil-borne Rhizoctonia infection in strain dependent manner. No connection was revealed between pathogenicity of strains and their origin or taxonomic position. However, the okra proved to be susceptible to strains highly pathogenic to other host plants as well. R. zeae, a species new to European flora, was as aggressive to okra as the most potent R. solani strains. The effect of Rhizoctonia infection was more prominent on mass accumulation in hypocotyls than in cotyledons. The protein content and glutathione S-transferase activity increased in parallel with the evolution of disease syndrome. Metalaxyl, an acetanilide type systemic antioomycete fungicide induced glutathione S-transferase activity in cotyledons with 24 hours a phase, and this induction was more outstanding in symptomless seedlings grown in Rhizoctonia infested soil. It might be concluded, that the stress response of plants in tolerant host/parasite pair takes effect at higher level than in susceptible relationships.

Induction of Maize Glutathione S-Transferase by Herbicide Safener and their Effect on Enzyme Activity against Chlorsulfuron

The acetolactate synthase(ALS) activity, glutathione S-transferase(GST) activity and glutathione(GSH) content in maize was investigated in response to treatments with safener (S)-3-dichloroacetyl-2,2-dimethyl-4-ethyl-1,3-oxazolidine. When induced by the chiral compound, the GSH content in root and shoot of maize increased 91.10% and 71.66%, respectively, the recovery rate of ALS activity reached 77%, and the GST activity increased 103.77%. The activity of maize GST was also assayed towards chlorsulfuron in vitro; the results showed that the induction of GST activity against chlorsulfuron of 14.54% was obtained. The enhancement of GST activity was found to be concomitant with changes in kinetic constants, which was related directly to the enzyme affinity for the CDNB substrate.

Antioxidant deficit in gills of Pacific oyster ( Crassostrea gigas) exposed to chlorodinitrobenzene increases menadione toxicity

Disturbances in antioxidant defenses decrease cellular protection against oxidative stress and jeopardize cellular homeostasis. To knock down the antioxidant defenses of Pacific oyster Crassostrea gigas, animals were pre-treated with 1-chloro-2,4-dinitrobenzene (CDNB) and further challenged with pro-oxidant menadione (MEN). CDNB pre-treatment (10 μM for 18 h) was able to consume cellular thiols in gills, decreasing GSH (53%) and decrease protein thiols (25%). CDNB pre-treatment also disrupted glutathione reductase and thioredoxin reductase activity in the gills, but likewise strongly induced glutathione S-transferase activity (270% increase). Surprisingly, hemocyte viability was greatly affected 24 h after CDNB removal, indicating a possible vulnerability of the oyster immune system to electrophilic attack. New in vivo approaches were established, allowing the identification of higher rates of GSH–CDNB conjugate export to the seawater and enabling the measurement of the organic peroxide consumption rate. CDNB-induced impairment in antioxidant defenses decreased the peroxide removal rate from seawater. After showing that CDNB decreased gill antioxidant defenses and increased DNA damage in hemocytes, oysters were further challenged with 1 mM MEN over 24 h. MEN treatment did not affect thiol homeostasis in gills, while CDNB pre-treated animals recovered GSH and PSH to the control level after 24 h of depuration. Interestingly, MEN intensified GSH and PSH loss and mortality in CDNB-pre-treated animals, showing a clear synergistic effect. The superoxide-generating one-electron reduction of MEN was predominant in gills and may have contributed to MEN toxicity. These results support the idea that antioxidant-depleted animals are more susceptible to oxidative attack, which can compromise survival. Data also corroborate the idea that gills are an important detoxifying organ, able to dispose of organic peroxides, induce phase II enzymes, and efficiently export GSH–CDNB conjugates.

Quantum dots enhance Cu2+-induced hepatic l02 cells toxicity: involvement of Nrf2

Both quantum dots- (QD) and copper- (Cu2+) induced reactive oxygen species (ROS) generation. The mechanisms underlying oxidative damage of combined QD and Cu were examined. Thus, the antioxidant enzyme glutathione-S-transferase (GST) enzyme activity and its genetic transcription regulator nuclear factor E2 (Nrf2) transcription factor expression was investigated in L02 cells. Addition of 2 µg mL−1 (IC10) QD enhanced Cu2+-induced GST activity and Nrf2 transcription factor levels by 35% and 86%, respectively. QD and Cu increased toxicity was also confirmed by cell morphology changes. The findings that QD- and/or Cu2+-induced toxicity enhanced GST via the Nrf2/antioxidant response element (ARE) pathway indicate that oxidant stress resulted in antioxidant responses being initiated in hepatic cells possibly as an adaptive mechanism.

The Mosquitocidal Activity of Methanolic Extracts of Lantana cramera Root and Anacardium occidentale Leaf: Role of Glutathione S-Transferase in Insecticide Resistance

Larvicidal activity of methanolic plant extracts of Lantana cramera (P1) root and Anacardium occidentale (P2) leaf was investigated against the larvae of the three mosquito species (Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti reared in the laboratory), and the respective glutathione S-transferase (GST) activity was analyzed as an index of protection against the extracts. The LC50 (extract concentration that shows 50% mortality) values of P1 extract for An. stephensi, Ae. aegypti, and Cx. quinquefasciatus were 132.55, 27.82, and 11.68 ppm, respectively, whereas those of P2 extract were 56.81, 912, and 10.79 ppm, respectively. In general, in the untreated groups, the level of GST activity was significantly higher in Ae. aegypti in comparison with An. stephesi and Cx. quinquefasciatus. However, the enzyme activity failed to show any response when treated with either of the plant extracts in Ae. aegypti. However, an increase in the GST activity was recorded in extract-treated larvae of both An. stephensi and Cx. quinquefasciatus. The results of the current study suggest that both the plant extracts show species-specific mosquitocidal potential. Induction of GST activities in survived An. stephensi and Cx. quinquefasciatus larvae suggests the role of this enzyme in conferring resistance to the plant extracts.

Differential effect of equal copper, cadmium and nickel concentration on biochemical reactions in wheat seedlings

Influence of 75 μM copper (Cu), cadmium (Cd) and nickel (Ni) on growth, tissue metal accumulation, non-protein thiols (NPT) and glutathione (GSH) contents, membrane damage, lipid peroxidation and protein oxidation as well as protease, glutathione S-transferase (GST) and peroxidase (POD) activities were studied in the shoots and roots of wheat seedlings after 7 days of metal exposure. The greatest growth reduction was found in response to Cu treatment; however accumulation of this metal in the wheat tissues was the lowest compared to the other metals used. All metals caused enhancement of electrolyte leakage from cells as well as increased lipid peroxidation and protein carbonylation. Proteolytic activity was enhanced only in Cu-exposed seedlings and in the roots it coincided with elevated protein carbonylation. The most pronounced increase in POD activity in the shoots was found after Ni treatment while in the roots in response to Cu. In contrast to Cu, application of Cd and Ni resulted in accumulation of NPT and induction of GST activity, which suggested involvement of these mechanisms in metal tolerance in wheat.

Drug interaction potential of the seed extract of Urtica urens L. (dwarf Nettle)

Dwarf nettle (Urtica urens) seed extract was examined in vivo in the rat for its potential to modulate drug metabolizing enzymes including aminopyrine N-demethylase (APND; CYP2C6), aniline 4-hydroxylase (A4H; CYP2E1), nitrosodimethylamine N-demethylase (NDMA-ND; CYP2E1) erythromycin N-demethylase (ERND; CYP3A1) CYP2D1/2 and glutathione S-transferase (GST). RT-PCR data and western blotting studies clearly demonstrated that CYP2C6 and CYP2E1 mRNA levels were substantially increased after Urtica treatment, while the level of CYP3A1 mRNA decreased and that of CYP2D1/2 remained unchanged. Urtica treatment significantly induced GST activity in the liver, lung and kidney (66-, 46- and 31-fold, respectively) while decreasing that of APND (35-, 61- and 94-fold) and NDMA-ND (23, 28 and 54-fold). ERND activity in liver was reduced 45-fold, but increased in the lung and kidney (78- and 144-fold) after Urtica treatment. These results indicate that Urtica seed extract may have the potential to inhibit and/or induce the metabolism of certain co-administered drugs.

Can the Activities of Acetylcholinesterase and Glutathione S-Transferases of Crangon crangon (L.) be Used as Biomarkers of Fuel Oil Exposure?

This work aimed to determine the sensitivity of acetylcholinesterase (AChE) and glutathione S-transferases (GST) activities of Crangon crangon (L.) to the water-accommodated fraction (WAF) of the fuel oil spilled by the oil tanker Prestige, in order to assess their usefulness as markers for this kind of pollution. Laboratory exposure of shrimps to WAF of weathered Prestige fuel oil showed no significant interference with AChE activity. Significant induction of GST activity was observed, potentially as a result of high concentrations of polycyclic aromatic hydrocarbons. However, these results were only obtained with the higher WAF concentrations tested. It was concluded that AChE and GST activities of C. crangon were not useful biomarkers for short-term exposure to the WAF of fuel oil spilled by the tanker Prestige and carried to the beaches of Galicia (NW Spain).

Abstract A43: Hops (humulus lupulus) induce detoxification enzymes in vivo

Abstract A43 Extracts of hop strobiles, the female parts of Humulus lupulus L., are popular botanical dietary supplements as alternative treatment for menopausal symptoms (1). Cancer preventive properties of hops, which are in part mediated through the induction of detoxification enzymes, have frequently been reported (2). This effect has been mainly attributed to one of its major constituents, xanthohumol (XN) (3). However, the chemopreventive effects have so far only been demonstrated in vitro and have not been confirmed in vivo. Therefore, we conducted an in vivo study in adult female rats and analyzed the effect of oral administration of a standardized hop extract (7.5 g extract/kg BW per day, containing 2% XN) or s.c. injection of XN (20 mg/day) on detoxification enzymes, such as NAD(P)H:quinone oxidoreductase 1 (NQO1) and glutathione-S-transferase (GST). Analysis of various tissues revealed that while pure XN and oral hops significantly induced NQO1 activity in liver and colon tissue, only oral hops and not pure xanthohumol induced NQO1 activity in the uterus. Interestingly, hops but not xanthohumol significantly induced GST activity in the liver and mammary gland suggesting that other hop constituents and/or an additional mechanism might be responsible for these effects. Transcription of many detoxification enzymes is regulated through the antioxidant response element (ARE) and its transcription factor Nrf2, which is repressed under basal conditions by Keap1 (4). It has been shown that XN alkylates Keap1 and therefore enhances the concentration of free Nrf2 in the nucleus which results in ARE activation (5). Another pathway leading to ARE activation is mediated by protein kinase C (PKC) that phosphorylates Nrf2 leading to accumulation of Nrf2 in the nucleus (6). To investigate whether this pathway is involved in the observations described above, additional experiments with HepG2-ARE-luciferase C8 cells were performed. The cells were treated with hop extract or XN with or without the selective PKC inhbitor, Ro-32-0432, and the ARE-luciferase induction was determined. The results revealed that hops- but not XN-regulated ARE induction is in part mediated by PKC. Possible active compounds are under investigation. These results suggest that hop dietary supplements have the potential as preventive agents against cancer through induction of detoxifying enzymes. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A43.

No acute toxicity to Uca pugnax, the mud fiddler crab, following a 96‐h exposure to sediment‐bound permethrin

In coastal areas, the application of pyrethroid insecticides and the resulting sediment residues pose a potential threat to marine benthic ecosystems. Pyrethroids cause acute toxicity and exhibit a wide range of sublethal effects on fish and crustaceans when exposure is aqueous. Fiddler crabs that inhabit salt marsh sediment are sensitive to sediment-associated pollutants and serve as a sentinel species for xenobiotic exposure. We exposed adult U. pugnax to salt marsh sediment spiked with different 60% trans/40% cis permethrin concentrations for 96 h, and evaluated changes in oxygen consumption rate, hemolymph osmolarity, and glutathione S-transferase activity (GST) following exposure. Marsh sediment was not lethal to U. pugnax at permethrin concentrations of 100-10,000 microg/kg. Sediment-bound permethrin had no significant effect on respiration and osmoregulation. Exposure caused an induction of hepatopancreas GST in a dose-dependent manner. Gill and midgut tissues showed induction at permethrin concentrations at 10,000 microg/kg. We conclude that short term exposure to permethrin-contaminated sediment does not pose a significant threat to this species or impact respiration and osmoregulation. Furthermore, increased GST activity allows us to evaluate this enzyme's induction as a generalist biomarker for sediment-bound pyrethroid exposures.

Protective effects of puerarin on carbon tetrachloride-induced hepatotoxicity

Puerarin, the main isoflavone glycoside found in the root of Pueraria lobata, has been used for various medicinal purposes in traditional Chinese medicine for thousands of years. The purpose of this study was to investigate the protective effects of puerarin against hepatotoxicity induced by carbon tetrachloride (CCl4) and the mechanism of its hepatoprotective effect. In mice, pretreatment with puerarin prior to the administration of CCl4 significantly prevented the increased serum enzymatic activity of alanine aspartate aminotransferase and hepatic malondialdehyde formation in a dose-dependent manner. In addition, pretreatment with puerarin significantly prevented both the depletion of reduced glutathione (GSH) content and the decrease in glutathione S-transferase (GST) activity in the liver of CCl4-intoxicated mice. Hepatic GSH levels and GST activity were increased by treatment with puerarin alone. CCl4-induced hepatotoxicity was also prevented, as indicated by liver histopathology. The effects of puerarin on cytochrome P450 (CYP) 2E1, the major isozyme involved in CCl4 bioactivation, were also investigated. Treatment of the mice with puerarin resulted in a significant decrease in the CYP2E1-dependent aniline hydroxylation in a dose-dependent manner. Consistent with these observations, the CYP2E1 protein levels were also lowered. Puerarin exhibited anti-oxidant effects on FeCl2-ascorbate induced lipid peroxidation in mouse liver homogenates, and on superoxide radical scavenging activity. These results suggest that the protective effects of puerarin against the CCl4-induced hepatotoxicity possibly involve mechanisms related to its ability to block CYP-mediated CCl4 bioactivation, induction of GST activity and free radical scavenging effects.

Modulation of N-Nitrosomethylbenzylamine Metabolism by Black Raspberries in the Esophagus and Liver of Fischer 344 Rats

: Dietary freeze-dried black raspberries (BRBs) inhibit N-nitrosomethylbenzylamine (NMBA)-induced tumorigenesis in the Fischer 344 rat esophagus. To determine the mechanistic basis of the anti-initiating effects of BRBs, NMBA metabolism was studied in esophageal explant cultures and in liver microsomes taken from rats fed with AIN-76A diet or AIN-76A diet containing 5% or 10% BRBs. Five percent and 10% dietary BRBs inhibited NMBA metabolism in explants (26% and 20%) and in microsomes (22% and 28%), but the inhibition was not dose dependent. To identify active inhibitory component(s) in BRBs, esophageal explants and liver microsomes from control rats were treated in vitro with an ethanol extract of BRBs or with individual components of BRBs [ellagic acid (EA) and two anthocyanins (cyanidin-3-glucoside and cyanidin-3-rutinoside)]. NMBA metabolism in explants was inhibited maximally by cyanidin-3-rutinoside (47%) followed by EA (33%), cyanidin-3-glucoside (23%), and the extract (11%). Similarly, in liver microsomes, the inhibition was maximal by cyanidin-3-rutinoside (47%) followed by EA (33%) and cyanidin-3-glucoside (32%). Phenylethylisothiocyanate (PEITC), a potent inhibitor of NMBA tumorigenesis in rat esophagus, was a stronger inhibitor of NMBA metabolism in vivo and in vitro than BRBs or their components. Dietary BRBs and PEITC induced glutathione S-transferase activity in the liver.

Glutathione S-transferases in the adaptation to plant secondary metabolites in theMyzus persicae aphid

Glutathione S-transferases (GST) in insects play an important role in the detoxification of many substances including allelochemicals from plants. Induction of GST activity in Myzus persicae in response to secondary metabolites from Brassica plants was determined using different host plant species and confirmed using artificial diet with pure allelochemicals added. The 2,4-dinitro-1-iodobenzene (DNIB) was found to be a useful substrate for identifying particular GSTs in insects. GSTs from M. persicae were purified using different affinity chromatography columns and related kinetic parameters were calculated. GST isoenzymes were characterised using electrophoretic methods. Although SDS-PAGE results indicated similarity among the purified enzymes from each affinity column, biochemical studies indicated significant differences in kinetic parameters. Finally, the GST pattern of M. persicae was discussed in terms of insect adaptation to the presence of plant secondary substances such as the glucosinolates and the isothiocyanates, from Brassicaceae host plants.

Inhibition of Azoxymethane-Induced Aberrant Crypt Foci in Rat by Diphenylmethyl Selenocyanate Through Downregulation of COX-2 and Modulation of Glutathione-S-transferase and Lipid Peroxidation

Preventive intervention of colorectal cancer has become essential, as a major portion of the population could develop the disease at some point during their lives. An inverse association between dietary intake of selenium, an important biological trace element, and colorectal cancer risk has been observed through epidemiological and experimental studies. Inhibitory activity of an organoselenocyanate, diphenylmethylselenocyanate, was tested on azoxymethane (15 mg/kg body wt) induced colon carcinogenesis in Sprague-Dawley rats. Pretreatment and concomitant treatment, at a dose of 2 mg/kg body wt, was carried out and the effect was observed on aberrant crypt foci, the preneoplastic lesion. To investigate the mechanism of action of the compound, lipid peroxidation level and glutathione-S-transferase (GST) activities were assessed in the liver as well as in the colon. Expression of cyclooxygenase-2 protein, inducible during colon carcinogenesis, was also analyzed in the colon. Inhibitory activity of the compound was shown by the reduced incidences of aberrant crypt foci in the treated groups (by 63.3%, p=0.00044 in the pretreated group, and by 44%, p=0.0067 in the concomitant treatment group). Significant induction of GST activities and significant reduction in lipid peroxidation level both in the liver as well as in the colon and suppression of cyclooxygenase-2 expression in the colon of the treated groups suggest that the compound could exert its preventive effect at different levels of the carcinogenic process. The preventive effect was better in the pretreatment group than in the concomitant treatment group, suggesting some added protection to the target tissue resulting from preadministration of the compound.