Elif Özcan Oruç

Evaluation of oxidative stress responses and neurotoxicity potential of diazinon in different tissues of Cyprinus carpio.

Toxicity of organophosphorus insecticides is mainly due to the inhibition of acetylcholinesterase, but, oxidative stress may be involved in the toxicity of this pesticides. Therefore, it was investigated whether diazinon, a commonly used organophosphate, may induce oxidative stress and cholinesterase inhibition in different tissues of Cyprinus carpio. Sublethal concentrations of diazinon (0.0036, 0.018 and 0.036ppb) were administired to C. carpio L. for 5, 15 and 30 days. The study was made by measuring biochemical stress responses of C. carpio L. spectrophotometrically taking into account acetylcholinesterase (AChE), Na(+)K(+)-adenosine triphosphatase (Na(+)K(+)-ATPase) and other antioxidant enzyme activities, as well as malondialdehyde and protein contents in gill, muscle and kidney tissues of the fish. Results of the study suggest that AChE (in gill and muscle tissues) and Na(+)K(+)-ATPase (in muscle and kidney tissues) activities decreased; that antioxidant enzymes, in particular superoxide dismutase (SOD), increased in gill, kidney and muscle tissues. We also observed the existence of a protective function of antioxidant enzymes against lipid peroxidation in muscle tissue. The changes in MDA content varied between increases and decreases in kidney tissue. In gill tissue, however, lipid peroxidation could not be prevented despite induction of SOD and glutathione peroxidase activities. We could see that the protein content decreased only in gill tissue as diazinon dosage was gradually increased until the 15th day of the experiment. During the period between 15th and the 30th days, the protein level in the fish was observed to have reached to that of the control group. This change in protein level can be attributed to adjustment of the fish to its new environmental conditions. Considering most of the parameters in tissues, it can be stated that diazinon exerted its effect at low concentration and during a long period of time, and its toxicity increased dose dependently. This study reveals that C. carpio developed tissue-specific adaptive response to neutralize the oxidative stress following pesticide exposure depending on different antioxidant levels in tissues and that SOD can be used as a biomarker in determining diazinon toxicity due to its early response at even low concentration levels.

Effects of diazinon on acetylcholinesterase activity and lipid peroxidation in the brain of Oreochromis niloticus

The aim of this study was to investigate the effects of organophosphorus (OP) pesticide diazinon on acetylcholinesterase (AChE: EC 3.1.1.7) activity and its relationship to lipid peroxidation (LPO) in the brain of a freshwater fish, Oreochromis niloticus. Malondialdehyde (MDA) content was used as biomarker for LPO. Fish were exposed to 1 and 2mg/L sublethal concentrations of diazinon for 1, 7, 15 and 30 days. In the entire experimental group, AChE activity in brain significantly decreased (up to 93% of control), whereas MDA content decreased after 1 day, and increased after 7 and 15 days of exposures. MDA was in similar level with the control group after diazinon exposure of 30 days. The findings of the present study show that diazinon inhibited AChE activity and it has LPO-inducing potential in fish. The inhibition of AChE activity in the brain of O. niloticus correlated with increased MDA levels after 7 and 15 days diazinon exposures (r=-0.661, P<0.019; r=-0.652, P<0.022, respectively).

Combined effects of 2,4-D and azinphosmethyl on antioxidant enzymes and lipid peroxidation in liver of Oreochromis niloticus

This study aims to investigate the effects of the herbicide 2,4-D and the insecticide azinphosmethyl on hepatic antioxidant enzyme activities and lipid peroxidation in tilapia. Fish were exposed to 27 ppm 2,4-D, 0.03 ppm azinphosmethyl and to a mixture of both for 24, 48, 72 and 96 h. Activities of catalase (EC 1.11.1.6), glutathione-S-transferase (GST, EC 2.5.1.18) and the level of malondialdehyde (MDA) in the liver of Oreochromis niloticus exposed to 2,4-D and azinphosmethyl, both individually and in combination, were not affected by the pesticide exposures. However, glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) and glutathione reductase (GR, EC 1.6.4.2) activities in individual and combined treatments, increased significantly compared to controls. Furthermore, glutathione peroxidase (GPx, EC 1.11.1.9) activity increased in individual treatment, while the same enzyme activity decreased in combination. 2,4-D did not affect the activity of superoxide dismutase (SOD, EC 1.15.1.1), but the activity of this enzyme in azinphosmethyl treatment decreased, while its activity increased in combination. Combined treatment of the pesticides exerted synergistic effects in the activity of SOD, while antagonistic effects were found in the activities of G6PD, GPx, GR. The results indicate that O. niloticus resisted oxidative stress by antioxidant mechanisms and prevented increases in lipid peroxidation.

Oxidative stress-related and ATPase effects of etoxazole in different tissues of Oreochromisniloticus

The aim of this study is to evaluate the effects of etoxazole, a new organofluorine acaricide-insecticide, on antioxidant enzyme activities, malondialdehyde content, and different adenosine triphosphatase (ATPase) activities in the gill, kidney and muscle tissues of freshwater fish, Oreochromisniloticus. Superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), Na(+), K(+)adenosine triphosphatase, Mg(2+)adenosine triphosphatase, Ca(2+)adenosine triphosphatase activities, and malondialdehyde (MDA) were measured spectrophotometrically in whole tissue homogenates of fish exposed to five different sublethal etoxazole concentrations (0.27, 0.54, 0.81, 1.08 and 1.35ppm) for 1, 7 and 15 days. Etoxazole did not cause oxidative stress. Increasing SOD activity in etoxazole-treated fish may be an important factor to restore susceptibility and to adapt to oxidative stress. Na(+), K(+)adenosine triphosphatase activities increase in gill and muscle tissues after etoxazole exposure while they reduce in kidney. Etoxazole treatment did not show significant alterations in Ca(2+) and Mg(2+)adenosine triphosphatase activities. These results suggest that etoxazole could not enhance the oxidative stress in O.niloticus. The effects of etoxazole were only observed at high concentrations and long treatment durations. Etoxazole may specifically have an effect on Na(+), K(+)adenosine triphosphatase activity, which could alter the ionic profiles of the cells in treated tissues.

Marker enzyme assesment in the liver of cyprinus carpio (L.) exposed to 2,4‐D and azinphosmethyl

The potential utility of antioxidant enzymes and lipid peroxidation as indicators of exposure to 2,4‐D and azinphosmethyl together with the toxic effects of these compounds in freshwater fish Cyprinus carpio were evaluated. Biochemical parameters were recorded spectrophotometrically in fish liver, which were exposed to a single dose of 2,4‐D and azinphosmehtyl (1/3 LC50), and their mixture at 1:1 ratio for 24, 48, 72, and 96 h. The most sensitive parameter was glutathione S‐transferase (GST) activity, which significantly increased with experimental exposures. Glucose 6‐phosphate dehydrogenase activity did not change after 24 and 48 h while there was an elevation after 72 h in all exposure groups. The activity decreased only when these were applied in combination at 96 h. Superoxide dismutase activity increased after azinphosmethyl exposure for 48 and 96 h. 2,4‐D decreased the activity after 24 h while the activity remained at the same level with control after 48 h. An elevation was found between 72 and 96 h. Mixture treatment did not changed the activity. Glutathione reductase and catalase enzyme activities, and malondialdehyde levels remained constant in all the treatment groups compared with controls. These results suggest that induction of GST activity may be used as biomarker for the assesment of water pollution in C. carpio.

Epigenetic mechanisms in the actions of endocrine-disrupting chemicals: gonadal effects and role in female reproduction.

There is a heightened interest and concern among scientists, clinicians and regulatory agencies as well as the general public, regarding the effects of environmental endocrine-disrupting chemicals (EDCs). In this review, we identify the main epigenetic mechanisms and describe key ovarian processes that are vulnerable to the epigenetic actions of EDCs. We also provide an overview of the human epidemiological evidence documenting the detrimental effects of several common environmental EDCs on female reproduction. We then focus on experimental evidence demonstrating the epigenetic effects of these EDCs in the ovary and female reproductive system, with an emphasis on methoxychlor, an organochlorine pesticide. We conclude the review by describing several critical issues in studying epigenetic effects of EDCs in the ovary, including transgenerational epigenetic effects.

Neurotoxicity Evaluation of the Organofluorine Pesticide Etoxazole in the Brain of Oreochromis niloticus

Etoxazole is a new organofluorine pesticide that has been used worldwide as acaricide and insecticide since 1998. Almost no previous attempt has been made to evaluate the toxic effects of etoxazole in vertebrates. Using fish (Oreochromis niloticus) as a suitable model organism, the aim of this study was to indicate whether etoxazole affects acetylcholinesterase and sodium potassium–activated adenosine triphosphatase activities in the brain tissue in order to evaluate the impacts on neurotoxicity and ion transportation. Enzyme activities were determined using spectrophotometric methods. At the sublethal concentrations (0.27, 0.54, 0.81, 1.08, 1.35 mg/L) and exposure durations (1, 7, 15 days) tested, etoxazole has no inhibitory effect on the brain acetylcholinesterase and sodium potassium–activated adenosine triphosphatase activities. Our results suggest that etoxazole and/or its metabolites may not reach or penetrate the blood–brain barrier; therefore, they do not essentially alter the functions of these two important enzymes for the brain.