Buket Alpertunga

The Proteasome Is an Integral Part of Solar Ultraviolet A Radiation-induced Gene Expression

Solar ultraviolet (UV) A radiation is a well known trigger of signaling responses in human skin fibroblasts. One important consequence of this stress response is the increased expression of matrix metalloproteinase-1 (MMP-1), which causes extracellular protein degradation and thereby contributes to photoaging of human skin. In the present study we identify the proteasome as an integral part of the UVA-induced, intracellular signaling cascade in human dermal fibroblasts. UVA-induced singlet oxygen formation was accompanied by protein oxidation, the cross-linking of oxidized proteins, and an inhibition of the proteasomal system. This proteasomal inhibition subsequently led to an accumulation of c-Jun and phosphorylated c-Jun and activation of activator protein-1, i.e. transcription factors known to control MMP-1 expression. Increased transcription factor activation was also observed if the proteasome was inhibited by cross-linked proteins or lactacystin, indicating a general mechanism. Most importantly, inhibition of the proteasome was of functional relevance for UVA-induced MMP-1 expression, because overexpression of the proteasome or the protein repair enzyme methionine sulfoxide reductase prevented the UVA-induced induction of MMP-1. These studies show that an environmentally relevant stimulus can trigger a signaling pathway, which links intracellular and extracellular protein degradation. They also identify the proteasome as an integral part of the UVA stress response.

Methiocarb-induced oxidative damage following subacute exposure and the protective effects of vitamin E and taurine in rats

Methiocarb, is used worldwide in agriculture and health programs. Besides its advantages in the agriculture, it causes several toxic effects. In this study, we aimed to investigate subacute effects of methiocarb on lipid peroxidation, reduced glutathione (GSH), antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd) and histopathological changes in rat tissues. Moreover, we examined the possible protective effects of vitamin E and taurine on methiocarb-induced oxidative damage in rat tissues. Rats were randomly divided into six groups as follows; I-control group; II-methiocarb group; III-vitamin E group; IV-vitamin E+methiocarb group; V-taurine group and VI-taurine+methiocarb group. Methiocarb significantly increased lipid peroxidation in liver and kidney when compared to control groups. Levels of GSH and activities of SOD, CAT and GSH-Px were found to be decreased, while GSH-Rd remained unchanged in rat liver and kidney treated with methiocarb. Pretreatment of vitamin E and taurine resulted in a significant decrease on lipid peroxidation, alleviating effects on GSH and antioxidant enzymes. The degenerative histological changes were less in liver than kidney of rats treated with methiocarb. Pretreatment of vitamin E and taurine showed a protective effect on the histological changes in kidney comparing to the liver of rats treated with methiocarb.

Acrylamide-induced oxidative stress in human erythrocytes

Acrylamide (AA), a widely used industrial chemical, is shown to be neurotoxic, mutagenic and carcinogenic. This study was carried out to investigate the effects of different doses of AA on lipid peroxidation (LPO), haemolysis, methaemoglobin (MetHb) and antioxidant system in human erythrocytes in vitro. Erythrocyte solutions were incubated with 0.10, 0.25, 0.50 and 1.00 mM of AA at 37°C for 1 hour. At the end of the incubation, malondialdehyde (MDA), an end product of LPO, was determined by liquid chromatography (LC) while total glutathione, reduced glutathione (GSH) levels, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) enzymes and the rates of haemolysis and MetHb were determined by spectrophotometric methods. All of the studied concentrations of AA increased MetHb formation and SOD activity, and induced MDA formation and haemolysis due to the destruction of erythrocyte cell membrane. AA caused a decrease in the activities of GSH-Px, CAT and GSH levels. However, these effects of AA were seen only at higher concentrations than AA intake estimated for populations in many countries. We suggest that LPO process may not be involved in the toxic effects of AA in low concentrations, although the present results showed that the studied concentrations of AA exert deteriorating effects on antioxidant enzyme activities, LPO process and haemolysis.

Determination of Commonly Used Herbicides in Surface Water Using Solid-Phase Extraction and Dual-Column HPLC-DAD

The present study describes the application of different solid-phase extraction techniques for the extraction, separation, and quantitative determination of 10 commonly used herbicides with different chemical structures (chlorsulfuron, diuron, bentazone, linuron, chlorpropham, fenoxoprop-ethyl, MCPA, diclofop-methyl, fluazifop-butyl, trifluraline) in water. Octadecyl (C18) Empore extraction disks, octadecyl (C18), and stryene divinylbenzene (SDB) Bond Elut Env cartridges were compared for solid-phase extraction efficiency. Herbicides were separated and quantified by reversed-phase high performance liquid chromatography with diode-array detection (HPLC-DAD) with simultaneous separation on two columns of differing polarity (C18 and CN) to confirm identification. Analytical separation was performed simultaneously on C18 and CN columns. Reanalysis of the sample extracts on a (cyano) CN column were used to confirm the identity of these compounds. Method optimization and validation parameters were presented in this work. Recoveries varied from 76.0% to 99.0% for C18 disks, from 75.1% to 100.0% for C18 cartridges, and from 54.0% to 98.0% for SDB cartridges over concentrations at 0.025–0.4 μg L−1. The limits of detection were 0.012–0.035 μg L−1.

Effects of methiocarb on lipid peroxidation and glutathione level in rat tissues

Methiocarb is an N-methylcarbamate insecticide used worldwide in agriculture and health programs. The aim of this study was to investigate the possible effects of methiocarb to induce lipid peroxidation (LPO) in tissues of male Wistar rats following single and repeated oral exposures. Animals were divided into six different groups, and methiocarb was administered by orally at doses 25, 10, and 2 mg/kg body weight for 1, 5, and 28 days, respectively. Liver, kidney, brain, and testis tissues were taken from the rats for the biochemical examinations. LPO and reduced glutathione (GSH) levels were determined in the tissues. LPO was significantly increased in liver, kidney, brain, and testis after 1-, 5-, and 28-day treatments of methiocarb. GSH levels were significantly increased in the 1-day period and significantly decreased in the 5- and 28-day periods in all tissues after methiocarb administration. It is concluded that methiocarb may induce LPO and produce disturbances on the GSH levels in liver, kidney, testis, and brain of rats. This suggests that methiocarb-induced toxicity may be associated with oxidative stress to cellular membranes. Further studies are required to better understand the role of oxidative stress on methiocarb-induced toxicity.

Liquid chromatographic analysis of maneb and its main degradation product, ethylenethiouera, in fruit juice

Ethylenethiourea (ETU), a possible human carcinogen and an antithyroid compound, is the main degradation product of the fungicide, maneb, which is widely used in agriculture. In this study, a rapid and accurate method for the determination of maneb and ETU in various fruit juices (tomato, grape and apple) was developed requiring minimal clean-up of sample extract, no derivatization prior to injection and no specialized LC detectors. Samples were cleaned up using silica and octadecylsilica (C18) cartridges before injection into liquid chromatography (LC) with diode-array detection (DAD). Recoveries ranged between 90 and 101% with relative standard deviations from 0.7 to 3.8%. The limits of determination of maneb and ETU were 0.1 and 0.01 mg l−1, respectively. The proposed method was used to monitor the presence of maneb and ETU in commercial samples taken from different markets of Istanbul, Turkey. Maneb was found in one tomato juice sample at a concentration of 0.45 mg l−1 but ETU was below the LOQ. Two tomato juices had no detectable maneb residue but contained ETU at levels of 0.08 and 0.11 mg l−1.

A photo artefact from linderazulene

Abstract Exposure of an ethanolic solution of linderazulene to direct sunlight yields the sesquiterpene keto-lactone 2 .

Acute effects of methiocarb on oxidative damage and the protective effects of vitamin E and taurine in the liver and kidney of Wistar rats

Methiocarb (MC) is a widely used carbamate pesticide in agriculture and health programs. Although the main molecular mechanism of carbamate toxicity involves acetylcholinesterase inhibition, studies have also implicated the induction of oxidative stress. Therefore, the present study was aimed to evaluate the effect of acute MC exposure on lipid peroxidation, antioxidant defense systems, histological changes in Wistar rats and the protective effect of pretreatment with vitamin E and taurine. A total of 48 rats were randomly divided into six groups. Rats in group I were given corn oil, while those in group III were dosed with vitamin E (100 mg/kg body weight (b.w.)) and in group V were dosed with taurine (50 mg/kg b.w.). Rats in group II were administered with MC only (25 mg/kg b.w., 1/4 of median lethal dose (LD50)), while those in groups IV and VI were pretreated with vitamin E (100 mg/kg b.w.) and taurine (50 mg/kg b.w.) for 20 days, respectively, and then exposed to MC (25 mg/kg b.w.). The rats administered with MC showed significant increase in the levels of malondialdehyde in the liver and kidney as an index of lipid peroxidation. Levels of glutathione and activities of superoxide dismutase, catalase and glutathione peroxidase were significantly increased, while activity of glutathione reductase remained unchanged in both the tissues after MC treatment. Mild degenerative histological changes were observed in liver tissue, while the changes in kidney tissue were more severe then liver after MC treatment. Pretreatment with vitamin E and taurine resulted in a significant decrease in the lipid peroxidation and alleviating effects on antioxidant defense systems in both the tissues, while protective effects on the histological changes were shown only in kidney when compared with liver. In conclusion, the study has demonstrated that the acute MC exposure in Wistar rats caused oxidative damage on liver and kidney, which were partly ameliorated by the pretreatment of vitamin E and taurine.

Polymorphisms in tumour necrosis factor alpha (TNFα) gene in patients with acute pancreatitis.

Proinflammatory cytokines, such as tumour necrosis factor α (TNFα), play fundamental roles in the pathogenesis of acute pancreatitis (AP). The aim of this study was to determine if polymorphisms in the TNFα gene are associated with AP. Two polymorphisms located in the promoter region (positions −308 and −238) in TNFα gene were determined using polymerase chain reaction- (PCR-) restriction fragment length polymorphism (RFLP) methods in 103 patients with AP and 92 healthy controls. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using logistic regression analysis adjusted for age, sex, BMI and smoking. The frequencies of TNFα polymorphisms were both similar in patients with mild or severe pancreatitis, so were in pancreatitis patients and in controls. We suggest that both SNPs of TNFα are not genetic risk factor for AP susceptibility (OR = 1.63; 95% CI: 1.13−4.01 for TNFα −308 and OR = 0.86; 95% CI: 0.75−1.77 for TNFα −238).

Determination of Triazines and N-Methylcarbamate Pesticides in Water by High-Performance Liquid Chromatography-Diode Array Detection

A rapid and selective method for the simultaneous determination of triazine herbicides (atrazine, its degradation product desethylatrazine, simazine, prometryn, terbutryn) and N-methylcarbamate insecticides (propoxur, carbaryl and methiocarb) in surface water has been developed. A 0.5 L of the water sample was preconcentrated by passage through a 1 g C18 solid-phase extraction cartridge. The retained compounds were eluted with 5 mL of methanol from the cartridge. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV diode-array detection. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C18 column. Prometryn and terbutryn were determined at 240 nm; propoxur, methiocarb at 204 nm and the others at 220 nm. Recoveries varied from 85 to 102% over concentrations at 0.025 and 0.2 µg L−1. The limits of detection for the compounds investigated are in the range of 0.005-0.012 µg L−1.