Changes in antioxidant defense systems induced by thiram in V79 Chinese hamster fibroblasts

Dynamics of the content of reactive oxygen species and the state of the glutathione system in the oral cavity during subchronic intoxication wuth the fungicide thiram and its antioxidant correction

Thiram is a dithiocarbamate derivative, which is used as a fungicide for seed dressing and spraying during the vegetation period of plants, and also as an active vulcanization accelerator in the production of rubber-based rubber products. In this study the content of reactive oxygen species (ROS) and the state of the glutathione system have been investigated in the oral fluid and gum tissues of adult male Wistar rats treated with thiram for 28 days during its administration with food at a dose of 1/50 LD50. Thiram induced formation of ROS in the oral cavity; this was accompanied by an imbalance in the ratio of reduced and oxidized forms of glutathione due to a decrease in glutathione and an increase in its oxidized form as compared to the control. Thiram administration caused an increase in the activity of glutathione-dependent enzymes (glutathione peroxidase, glutathione transferase, and glutathione reductase). However, the time-course of enzyme activation in the gum tissues and oral fluid varied in dependence on the time of exposure to thiram. In the oral fluid of thiram-treated rats changes in the antioxidant glutathione system appeared earlier. The standard diet did not allow the glutathione pool to be fully restored to physiological levels after cessation of thiram intake. The use of exogenous antioxidants resviratrol and an Echinacea purpurea extract led to the restoration of redox homeostasis in the oral cavity.

Thiram exposure in environment: A critical review on cytotoxicity

Thiram is used in large quantities in agriculture and may contaminate the environment by improper handling or storage in chemical plants and warehouses. A review of the literature has shown that thiram can affect different organs in animals and its toxic mechanisms can be elucidated in more detail at molecular level. We have summarized several impacts of thiram on animals: the effects of the perspectives of oxidative stress, mitochondrial damage, autophagy, apoptosis, and the IHH/PTHrP pathway on regulating abnormal skeletal development in particular tibial dyschondroplasia and kyphosis; angiogenesis inhibition was investigated from the perspective of angiogenesis factor inhibition, PI3K/AKT signaling pathway and CD147; the inhibition effect of thiram on fibroblasts and erythrocytes via the perspective of oxidative stress, mitochondrial damage and inhibition of growth factors in animal skin fibroblasts and erythrocytes; studied fertilized egg size, reduced fertility, neurodegeneration, and immune damage from the perspectives of CYP51 inhibition and dopamine-b-hydroxylase inhibition in the reproductive system, vitamin D deficiency in the nervous system, and inflammatory damage in the immune system; embryonic dysplasia in terms of thyroid hormone repression in animal embryonic development and repression of the SOX9a transcription factor. The elucidation of the mechanisms of toxicity of thiram on various organs of animals at molecular level will enable a more detailed understanding of the mechanisms of toxicity of thiram in animals and will facilitate the exploration of the treatment of thiram poisoning at molecular level.

Residue of thiram in food, suppresses immune system stress signals and disturbs sphingolipid metabolism in chickens

Thiram, a well-known sulfur containing organic compound is frequently and extensively used in agriculture because of high biological activity to control different pests. In certain cases, due to long persistence in the environment pesticides and other environmental contaminants induce undesirable toxic impacts to public health and environment. To ascertain the potential mechanisms of toxicity of thiram on different immune organs of broilers, a total of 100 one-day-old chicks were obtained and randomly divided into two groups including thiram group (50 mg/kg) and untreated control group. Thymus and spleen tissues were collected at the age of 14 days from the experimental birds. At necropsy level, thymus was congested, enlarged and hyperemic while spleen had no obvious lesions. The results on mechanisms (apoptosis and autophagy) of immunotoxicity showed significantly increased expression of bax, caspase3, cytc, ATG5, beclin1 and p62 in spleen of treated mice. Results indicated significantly decreased expression of m-TOR and bcl2 to activate apoptosis and autophagy. The expressions of bax, p53 and m-TOR were up-regulated in the thymus while the expressions of ATG5 and Beclin1 were down-regulated to mediate cell apoptosis and inhibit autophagy. The results on different metabolome investigation showed that the sphingolipid metabolism in the thymus of chicks exposed to thiram was disrupted resulting in up-regulation of metabolites related to cell membrane components such as SM, galactosylceramide and lactosylceramide. The results of our experimental research suggest that thiram can interfere with the sphingolipid metabolism in thymus and angiogenesis, inhibit the proliferation of vascular endothelial cells to induce potential toxic effects in chicken.

Oral administration of thiram inhibits brush border membrane enzymes, oxidizes proteins and thiols, impairs redox system and causes histological changes in rat intestine: A dose dependent study

Pesticides are extensively employed worldwide, especially in agriculture to control weeds, insect infestation and diseases. Besides their targets, pesticides can also affect the health of non-target organisms, including humans The present study was conducted to study the effect of oral exposure of thiram, a dithiocarbamate fungicide, on the intestine of rats. Male rats were administered thiram at doses of 100, 250, 500 and 750 mg/kg body weight for 4 days. This treatment reduced cellular glutathione, total sulfhydryl groups but enhanced protein carbonyl content and hydrogen peroxide levels. In addition, the activities of all major antioxidant enzymes (catalase, thioredoxin reductase, glutathione peroxidase and glutathione-S-transferase) except superoxide dismutase were decreased. The antioxidant power of the intestine was impaired lowering the metal-reducing and free radical quenching ability. Administration of thiram also led to inhibition of intestinal brush border membrane enzymes, alkaline phosphatase, γ-glutamyl transferase, leucine aminopeptidase and sucrase. Activities of enzymes of pentose phosphate pathway, citric acid cycle, glycolysis and gluconeogenesis were also inhibited. Histopathology showed extensive damage in the intestine of thiram-treated rats at higher doses. All the observed effects were in a thiram dose-dependent manner. The results of this study show that thiram causes significant oxidative damage in the rat intestine which is associated with the marked impairment in the antioxidant defense system.

Assessing the effects of Thiram to oxidative stress responses in a freshwater bioindicator cladoceran (Daphnia magna)

Thiram (TMTD) is able to induce antioxidant defense and oxidative stress in different organisms. Moreover, Thiram can act as a prooxidant resulting in the formation of reactive oxygen species (ROS). To our knowledge, this is the first study assessing the oxidative stress induced by Thiram in the cladoceran Daphnia magna. At present, literature focus on the determination of toxicity in vertebrate organisms or cells, however, very few studies were interested to evaluate Thiram's effects in aquatic organisms such as cladoceran. To assess these effects, antioxidant GSH content, CAT and GST enzyme activities, cellular damages and lipid peroxidation indicators (MDA) were evaluated as oxidative stress biomarkers. Our results showed that acute Thiram exposure resulted in significant biochemical responses, demonstrating that Thiram induced oxidative damage. Indeed, following exposure to Thiram, we noticed an intracellular (GSH) depletion, associated with a marked increase of lipid membrane peroxidation as shown by high (MDA) production. Moreover, a dose-dependent induction of antioxidant key enzymes (CAT) and (GST) was found which led to an oxidative stress and finally death of Daphnia magna.

Thiram-induced cytotoxicity and oxidative stress in human erythrocytes: an in vitro study

Tetramethylthiuram disulfide, commonly known as thiram, is an organosulfur compound which is used as a bactericide, fungicide and ectoparasiticide to prevent disease in seeds and crops. Being a fungicide there is a high probability of human occupational exposure to thiram and also via consumption of contaminated food. In this work, the cytotoxicity of thiram was studied under in vitro conditions using human erythrocytes as the cellular model. Erythrocytes were incubated with different concentrations of thiram (25-500 μM) for 4 h at 37 °C. Control cells (thiram untreated) were similarly incubated at 37 °C. Whole cells and hemolysates were analyzed for various biochemical parameters. Treatment of erythrocytes with thiram increased protein and lipid oxidation and hydrogen peroxide level in hemolysates but decreased glutathione and total sulfhydryl group content. This was accompanied by hemoglobin oxidation, heme degradation and release of free iron. Activities of all major antioxidant enzymes were inhibited. The antioxidant power of thiram treated erythrocytes was lowered resulting in decreased metal reducing and free radical quenching ability. These results suggest that thiram enhances the generation of reactive species that cause oxidative modification of cell components. This was confirmed by experiments that showed enhanced generation of reactive oxygen and nitrogen species in thiram treated erythrocytes. Activities of marker enzymes of glucose metabolism and erythrocyte membrane were also inhibited. All effects were seen in a thiram concentration-dependent manner. Electron microscopy further supported the damaging effect of thiram on erythrocytes. Thus thiram induces oxidative stress condition in human erythrocytes and causes oxidative modification of cell components.

The protective effects of silybin on the cytotoxicity of thiram in human, rat and chicken cell cultures

The study objective was a determination of thiram cytotoxicity and silybin cytoprotective activity in course of the fungicide impact on cell metabolism and membrane integrity. Firstly, human, rat, chicken hepatoma cells and rat myoblasts cultures were incubated with thiram. The results showed higher sensitivity of myoblasts on thiram exposure than the hepatoma cells. Among hepatoma cells, the chicken cultures were the most sensitive on the fungicide endangering. The mitochondrial activity was the most thiram affected function within all types the cell lines used. When silybin co-acted with thiram, an increase of the cell viability was recorded. The EC₅₀-values were higher for thiram subjected to interaction with silybin than the effect of alone thiram action. The interaction mode between the studied compounds shown by combination index (CI) represented an antagonistic or an additive nature and was depended on thiram concentration, type of the cells and the assay used. Moreover, the morphology changes were dependent on silybin presence in the cell cultures subjected to thiram impact at the same time. Staining with Hoechst 33342 and propidium ioidium revealed the apoptosis cell death in the incubation cultures. Definitely, the results have shown a potential of silybin to protect the cultured cells in course of cytotoxicity induced by thiram. However, future studies taking into account other endpoints of thiram cytotoxicity pathways including species differences and the cytoprotection efficacy could be of interest.

Traumatic Acid Reduces Oxidative Stress and Enhances Collagen Biosynthesis in Cultured Human Skin Fibroblasts

Traumatic acid (TA) is a plant hormone (cytokinin) that in terms of chemical structure belongs to the group of fatty acids derivatives. It was isolated from Phaseolus vulgaris. TA activity and its influence on human cells and organism has not previously been the subject of research. The aim of this study was to examine the effects of TA on collagen content and basic oxidative stress parameters, such as antioxidative enzyme activity, reduced glutathione, thiol group content, and lipid peroxidation in physiological conditions. The results show a stimulatory effect of TA on tested parameters. TA caused a decrease in membrane phospholipid peroxidation and exhibited protective properties against ROS production. It also increases protein and collagen biosynthesis and its secretion into the culture medium. The present findings reveal that TA exhibits multiple and complex activity in fibroblast cells in vitro. TA, with its activity similar to unsaturated fatty acids, shows antioxidant and stimulatory effects on collagen biosynthesis. It is a potentially powerful agent with applications in the treatment of many skin diseases connected with oxidative stress and collagen biosynthesis disorders.

Adverse effects of thiram-treated seed ingestion on the reproductive performance and the offspring immune function of the red-legged partridge

Pesticide research traditionally has focused on compounds with high acute toxicity or persistence, but the adverse sublethal effects of pesticides with different properties also may have important consequences on exposed wildlife. The authors studied the effects of thiram, a fungicide used for seed coating with known effects as endocrine disruptor. Red-legged partridges (Alectoris rufa; n = 15 pairs per treatment group) were fed wheat treated with 0%, 20%, or 100% of the thiram application rate used in autumn (25 d) and late winter (10 d) to mimic cereal sowing periods. The authors studied the effects on reproductive performance, carotenoid-based ornamentation and cellular immune responsiveness of adult partridges, and their relationship with changes in oxidative stress biomarkers and plasma biochemistry. The authors also studied the effect of parental exposure on egg antioxidant content and on the survival, growth, and cellular immune response of offspring. Exposure to thiram-coated seeds delayed egg laying, reduced clutch size, and affected egg size and eggshell thickness. Partridges exposed to the 20% thiram dose exhibited reduced egg fertility and brood size (55% and 28% of controls, respectively). Chick survival was unaffected by parental exposure to treated seeds, but adverse effects on their growth rate and cellular immune response were apparent. These effects on reproduction and immune function may have important demographic consequences on farmland bird populations.

Thiram activates NF-kappaB and enhances ICAM-1 expression in human microvascular endothelial HMEC-1 cells

Thiram (TMTD) is a fungicidal and bactericidal agent used as antiseptic, seed disinfectant and animal repellent. In the light of known properties, thiram is considered to be used as an inhibitor of angiogenesis and/or inflammation. Since angiogenesis requires the growth of vascular endothelial cells we have used microvascular endothelial cell line HMEC-1 to elucidate the effect of thiram on normal and stimulated cells. We cultured HMEC-1 cells in the presence of thiram at low concentration (0.5 µg/mL or 2 µg/mL) (0.2 µM or 0.8 µM) or TNF-α (10 ng/mL) alone, and thiram together with TNF-α. TNF-α was used as a cytokine that triggers changes characteristic for inflammatory state of the cell. We carried out an in vitro study aimed at assessing generation of reactive oxygen species (ROS), activation of NF-κB, and expression of cell adhesion molecules ICAM-1, VCAM-1, PECAM-1. It was found that TMTD produced ROS and activated NF-κB. Activation of NF-κB was concurrent with an increase in ICAM-1 expression on the surface of HMEC-1 cells. ICAM-1 reflects intensity of inflammation in endothelial cell milieu. The expression of VCAM-1 and PECAM-1 on these cells was not changed by thiram. It was also found that stimulation of the HMEC-1 cells with the pro-inflammatory cytokine TNF-α caused activation of ICAM-1 and VCAM-1 expression with concomitant decrease of PECAM-1 cell surface expression above the control levels. Treatment with thiram and TNF-α changed cellular response compared with effects observed after treatment with TNF-α alone, i.e. further increase of ICAM-1 expression and impairment of the TNF-α effect on PECAM-1 and VCAM-1 expression. This study demonstrated that thiram acts as a pro-oxidant, and elicits in endothelial cell environment effects characteristic for inflammation. However, when it is present concurrently with pro-inflammatory cytokine TNF-α interferes with its action.

Sphaerophysa kotschyana, an endemic species from Central Anatolia: antioxidant system responses under salt stress

Sphaerophysa kotschyana is a Turkish endemic and endangered plant that grows near Salt Lake, in Konya, Turkey. However, little is known about the ability of this plant to generate/remove reactive oxygen species (ROS) or its adaptive biochemical responses to saline environments. After exposure of S. kotschyana to 0, 150, and 300 mM NaCl for 7 and 14 days, we investigated (1) the activities and isozyme compositions of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), and glutathione reductase (GR); (2) the oxidative stress parameters NADPH oxidase (NOX) activity, lipid peroxidation (MDA), total ascorbate (tAsA) content, and total glutathione content (tGlut); and (3) ROS levels for superoxide anion radical (O 2 (·-) ), hydrogen peroxide (H2O2), hydroxyl radicals (OH·), and histochemical staining of O 2 (·-) and H2O2. H2O2 content increased after 14 days of salt stress, which was consistent with the results from histochemical staining and NOX activity measurements. In contrast, oxidative stress induced by 150 mM NaCl was more efficiently prevented, as indicated by low malondialdehyde (MDA) levels and especially at 7 days, by increased levels of SOD, POX, APX, and GR. However, at 300 mM NaCl, decreased levels of protective enzymes such as SOD, CAT, POX, and GR, particularly with long-term stress (14 days), resulted in limited ROS scavenging activity and increased MDA levels. Moreover, at 300 mM NaCl, the high H2O2 content caused oxidative damage rather than inducing protective responses against H2O2. These results suggest that S. kotschyana is potentially tolerant to salt-induced damage only at low salt concentrations.

Experimental exposure of red-legged partridges (Alectoris rufa) to seeds coated with imidacloprid, thiram and difenoconazole

Pesticide coated seeds are commonly used in agriculture, and may be an important source of food for some birds in times of scarcity, as well as a route of pesticide ingestion. We tested the lethal and sub-lethal effects of treated seed ingestion by the red-legged partridge (Alectoris rufa), a game bird of high socio-economic value in Spain. One year-old partridges (n = 42 pairs) were fed for 10 days in spring (prior to breeding) with wheat treated with difenoconazole (fungicide), thiram (fungicide) or imidacloprid (insecticide), using two doses for each pesticide (the one recommended, and its double to represent potential cases of abuse of pesticides). We investigated the direct and indirect effects on the body condition, physiology, immunology, coloration and subsequent reproduction of exposed partridges. For the latter, eggs were collected, measured and incubated and the growth and survival of chicks were monitored. Thiram and imidacloprid at high exposure doses produced mortalities of 41.6 and 58.3 %, respectively. The first death was observed at day 3 for imidacloprid and at day 7 for thiram. Both doses of the three pesticides caused sublethal effects, such as altered biochemical parameters, oxidative stress and reduced carotenoid-based coloration. The high exposure doses of imidacloprid and thiram also produced a decrease in cellular immune response measured by the phytohemagglutinin test in males. Bearing in mind the limitation of the small number of surviving pairs in some treatments, we found that the three pesticides reduced the size of eggs and imidacloprid and difenoconazole also reduced the fertilization rate. In addition, both thiram and imidacloprid reduced chick survival. These experiments highlight that the toxicity of pesticide-treated seeds is a factor to consider in the decline of birds in agricultural environments.

Chromosomal aberrations in cultured human lymphocytes treated with the fungicide, Thiram

In vitro effects of different concentrations of Thiram were tested on human lymphocytes to determine, by means of the chromosome aberrations (CAs) assay, whether this fungicide could induce clastogenic damage. Evidences of the effect of Thiram on human lymphocytes were limited to sister chromatid exchange, micronuclei formation, and comet assays. We evaluated 0.01, 0.1, 1.2, and 12.0 μg/mL of Thiram, where 0.01 μg/mL represent the acceptable daily intake dose set by the World Health Organization and the Food and Agriculture Organization for fruit and vegetables, whereas 0.1, 1.2, and 12.0 μg/mL are its multiple values. Results indicated that human lymphocytes treated in vitro with Thiram at concentrations of 1.20 and 12.0 μg/mL significantly increased CAs frequency, compared with the negative control, whereas at lower concentrations (0.01 and 0.1 μg/mL), this effect was not observed. However, Thiram showed a clastogenic effect also at the concentration value of 1.2 μg/mL that represents a lower value with respect to the residue limits found in Italy for grapes, strawberries, potatoes, tobacco, and other fruits and vegetables. Finally, according to some evidence obtained from the study of other fungicides, Thiram produced a significant reduction in the mitotic index with increasing concentration.

Regulation of hypoxia inducible factor-1α expression by the alteration of redox status in HepG2 cells

Hypoxia inducible factor-1 (HIF-1) has been considered as a critical transcriptional factor in response to hypoxia. It can increase P-glycoprotein (P-Gp) thus generating the resistant effect to chemotherapy. At present, the mechanism regulating HIF-1α is still not fully clear in hypoxic tumor cells. Intracellular redox status is closely correlated with hypoxic micro-environment, so we investigate whether alterations in the cellular redox status lead to the changes of HIF-1α expression. HepG2 cells were exposed to Buthionine sulphoximine (BSO) for 12 h prior to hypoxia treatment. The level of HIF-1α expression was measured by Western blot and immunocytochemistry assays. Reduce glutathione (GSH) concentrations in hypoxic cells were determined using glutathione reductase/5,5^'-dithiobis-(2-nitrob-enzoic acid) (DTNB) recycling assay. To further confirm the effect of intracellular redox status on HIF-1α expression, N-acetylcysteine (NAC) was added to culture cells for 8 h before the hypoxia treatment. The levels of multidrug resistance gene-1 (MDR-1) and erythropoietin (EPO) mRNA targeted by HIF-1α in hypoxic cells were further determined with RT-PCR, and then the expression of P-Gp protein was observed by Western blotting. The results showed that BSO pretreatment down-regulated HIF-1α and the effect was concentration-dependent, on the other hand, the increases of intracellular GSH contents by NAC could partly elevate the levels of HIF-1α expression. The levels of P-Gp (MDR-1) and EPO were concomitant with the trend of HIF-1α expression. Therefore, our data indicate that the changes of redox status in hypoxic cells may regulate HIF-1α expression and provide valuable information on tumor chemotherapy.

Protective effect of N-acetyl-L-cysteine against disulfiram-induced oxidative stress and apoptosis in V79 cells

This work investigated the effect of N-acetyl-L-cysteine (NAC) on disulfiram (DSF) induced oxidative stress in Chinese hamster fibroblast cells (V79). An increase in oxidative stress induced by DSF was observed up to a 200 μM concentration. It was evidenced by a statistically significant increase of both GSH(t) and GSSG levels, as well as elevated protein carbonyl (PC) content. There was no increase in lipid peroxidation (measured as TBARS). DSF increased CAT activity, but did not change SOD1 and SOD2 activities. Analysis of GSH related enzymes showed that DSF significantly increased GR activity, did not change Se-dependent GPx, but statistically significantly decreased non-Se-dependent GPx activity. DSF showed also pro-apoptotic activity. NAC alone did not produce any significant changes, besides an increase of GSH(t) level, in any of the variables measured. However, pre-treatment of cells with NAC ameliorated DSF-induced changes. NAC pre-treatment restored the viability of DSF-treated cells evaluated by Trypan blue exclusion assay and MTT test, GSSG level, and protein carbonyl content to the control values as well as it reduced pro-apoptotic activity of DSF. The increase of CAT and GR activity was not reversed. Activity of both GPx was significantly increased compared to their values after DSF treatment. In conclusion, oxidative properties are at least partially attributable to the cellular effects of disulfiram and mechanisms induced by NAC pre-treatment may lower or even abolish the observed effects. These observations illustrate the importance of the initial cellular redox state in terms of cell response to disulfiram exposure.

Cytotoxicity and chromosomal aberrations induced by acrylamide in V79 cells: role of glutathione modulators

Acrylamide (AA) is a suspected human carcinogen found to be generated during the heating of carbohydrate-rich foodstuffs. AA exhibits 'Michael-type' reactivity towards reduced glutathione (GSH), resulting in vivo in the urinary excretion of mercapturic acid conjugates. GSH is a key factor for mammalian cell homeostasis, with diverse functions that include, among others, the conjugation of electrophilic compounds and the detoxification of products generated by oxidative stress. Therefore, studies focusing on the modulation of GSH are of great importance for the understanding of the mechanisms of AA-induced toxicity. This report addresses this issue by analyzing cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) reduction assay) and clastogenicity (chromosomal aberrations) as endpoints in V79 cells after exposure to AA. The experiments described herein include the evaluation of the effect of buthionine sulfoximine (BSO), an effective inhibitor of GSH synthesis, GSH-monoethyl ester (GSH-EE), a compound that is taken up by cells and intracellularly hydrolysed to GSH, and also GSH exogenously added to culture medium. Pre-treatment with BSO increased the cytotoxicity and the frequency of aberrant cells excluding gaps (ACEG) induced by AA. While pre-treatment with GSH-EE did not modify the cytotoxicity or the frequency of ACEG induced by AA, co-treatment with AA and GSH decreased both parameters, rendering the cells less prone to the toxic effects of AA. In vitro studies in a cell-free system, using monochlorobimane (MCB), a fluorescent probe for GSH, were also performed in order to evaluate the role of AA in GSH depletion. The results show that spontaneous conjugation of AA with GSH in the extracellular medium is involved in the protection given by GSH. In summary, these results reinforce the role of GSH in the modulation of the cytotoxic and clastogenic effects induced by AA, which may be relevant in an in vivo exposure scenario.