Loss of membrane integrity and inhibition of type-I iodothyronine 5'-monodeiodinase activity by fenvalerate in female mouse

Pyrethroids and developmental neurotoxicity - A critical review of epidemiological studies and supporting mechanistic evidence

BACKGROUND

Pyrethroid metabolites are widely detectable in urine from the general population, including pregnant women and children. Pyrethroids are neurotoxic and suggested endocrine disruptors. Exposure during vulnerable developmental time windows may have long-term impacts on neurodevelopment.

OBJECTIVE

To evaluate the epidemiological evidence for neurodevelopmental effects related to prenatal and childhood pyrethroid exposure in a systematic review and to assess biological plausibility by evaluating mechanistic evidence.

METHODS

We searched PubMed and Web of Science up to September 1, 2021 and included original studies published in English in which pyrethroid exposure was measured or estimated during pregnancy or childhood and associations with neurodevelopmental outcomes in the children were investigated. The Navigation Guide Systematic Review Methodology was used to evaluate the epidemiological evidence. For mechanistic evidence, we focused on relevant key events (KEs) suggested in Adverse Outcome Pathways (AOPs) using the OECD-supported AOP-wiki platform. A systematic search combining the KEs with pyrethroids, including 26 individual compounds, was performed in the ToxCast database.

RESULTS

Twenty-five epidemiological studies met the inclusion criteria, 17 presented findings on prenatal exposure, 10 on childhood exposure and two on both exposure windows. The overall body of evidence was rated as "moderate quality" with "sufficient evidence" for an association between prenatal pyrethroid exposure and adverse neurodevelopment. For childhood exposure, the overall rating was "low quality" with "limited evidence" because of cross-sectional study design. Regarding mechanistic evidence, we found that pyrethroids are able to interfere with neurodevelopmental KEs included in established AOPs for adverse neurodevelopmental. The evidence was strongest for interference with thyroid hormone (TH) function.

CONCLUSION

Pyrethroids are probably human developmental neurotoxicants and adverse impacts of pyrethroid exposure on neurodevelopment are likely at exposure levels occurring in the general population. Preventive measures to reduce exposure among pregnant women and children are warranted.

Key role of mitochondrial mutation Leu107Ser (COX1) in deltamethrin resistance in salmon lice (Lepeophtheirus salmonis)

The pyrethroid deltamethrin (DTM) is used to treat Atlantic salmon (Salmo salar) against salmon louse (Lepeophtheirus salmonis) infestations. However, DTM resistance has evolved in L. salmonis and is currently common in the North Atlantic. This study aimed to re-assess the association between DTM resistance and mitochondrial (mtDNA) mutations demonstrated in previous reports. Among 218 L. salmonis collected in Scotland in 2018–2019, 89.4% showed DTM resistance in bioassays, while 93.6% expressed at least one of four mtDNA single nucleotide polymorphisms (SNPs) previously shown to be resistance associated. Genotyping at further 14 SNP loci allowed to define three resistance-associated mtDNA haplotypes, named 2, 3 and 4, occurring in 72.0%, 14.2% and 7.3% of samples, respectively. L. salmonis strains IoA-02 (haplotype 2) and IoA-10 (haplotype 3) both showed high levels (~ 100-fold) of DTM resistance, which was inherited maternally in crossing experiments. MtDNA haplotypes 2 and 3 differed in genotype for 17 of 18 studied SNPs, but shared one mutation that causes an amino acid change (Leu107Ser) in the cytochrome c oxidase subunit 1 (COX1) and was present in all DTM resistant while lacking in all susceptible parasites. We conclude that Leu107Ser (COX1) is a main genetic determinant of DTM resistance in L. salmonis.

Oxidative Stress-induced Toxicity and DNA Stability in Some Agri-field Based Livestock/Insect by Widely used Pesticides

AIM AND OBJECTIVE

Humans continuously use pesticides in the field to control the pest population and weeds for considerable agricultural productivity. Side-by species like grazinganimals, insects and other species are adversely affected by or become resistant to pesticides. Insects, birds and cattle are highly abundant dwellers of the agriculture-field and represent three distinct phyla having versatile physiological features. Besides higher agricultural-productivity, protection to several species will maintain ecological/environmental balance. Studies on the effect of widely used pesticides on their DNA-stability and important enzymatic-activities are insufficient.

MATERIALS AND METHODS

Antioxidant-activity (Superoxide-dismutase; SOD/Catalase- by gelzymogram- assay) and DNA-stability (fragmentation-assay) in hepatic/gut tissues were studied after in vitro exposure of Chlorpyrifos, Fenvalerate, Nimbecidine or Azadirachtin to goat/cow/poultry-hen/insect.

RESULTS

In general, all pesticides were found to impair enzymatic-activities. However, lower organisms were affected more than higher vertebrates by azadirachtin-treatment. DNA fragmentation was found more in insects/poultry-birds than that of the cattle in hepatic/gut tissues. Inversely, toxicity/antioxidant marker-enzymes were more responsive in insect gut-tissues. However, mitochondrialtoxicity revealed variable effects on different species. It has been noticed that chlorpyrifos is the most toxic pesticide, followed by Fenvalerate/Nimbecidine (Azadirachtin, AZT). Nevertheless, AZT revealed its higher DNA-destabilizing effects on the field-insects as compared to the other animals.

CONCLUSION

Field-insects are highly integrated into the ecosystem and the local bio-geo-chemical cycle, which may be impaired. Pesticides may have toxic effects on higher vertebrates and may sustain in the soil after being metabolized into their different derivatives. Some of the sensitive biochemical parameters of this organism may be used as a biomarker for pesticide toxicity.

Urinary metabolites of non-persistent pesticides and serum hormones in Spanish adolescent males

OBJECTIVE

To assess the relationship of urinary concentrations of ethylenethiourea (ETU), the main degradation product of ethylene bis-dithiocarbamate fungicides, 3-phenoxybenzoic acid (3-PBA), a common metabolite of many pyrethroids, and 1-naphthol (1N), a metabolite of the carbamate insecticide carbaryl, with hormone concentrations in adolescent males; and to examine interactions between pesticide metabolites and polymorphisms in xenobiotic metabolizing enzymes, including CYP2C19 and CYP2D6, in relation to hormone concentrations.

METHODS

A cross-sectional study was conducted in 134 males from the Spanish Environment and Childhood (INMA)-Granada cohort. Urine and serum samples were collected from participants during the same clinical visit at the age of 15-17 years. First morning urine void was analyzed for concentrations of ETU, 3-PBA, and 1N. Serum was analyzed for concentrations of reproductive hormones (testosterone, 17β-estradiol [E₂], dehydroepiandrosterone sulfate [DHEAS], sex hormone binding globulin [SHBG], luteinizing hormone [LH], follicle stimulating hormone [FSH], anti-Müllerian hormone [AMH], and prolactin), thyroid hormones (free thyroxine [FT4], total triiodothyronine [TT3], and thyroid stimulating hormone [TSH]), insulin growth factor 1 (IGF-1), adrenocorticotropic hormone (ACTH), and cortisol. CYP2C19 G681A and CYP2D6 G1846A polymorphisms were determined in blood from 117 participants. Multiple linear regression, interaction terms, and stratified analyses were performed.

RESULTS

Urinary ETU was detected in 74.6% of participants, 1N in 38.1%, and 3-PBA in 19.4%. Positive associations between detectable 3-PBA and TT3 and between detectable 1N and DHEAS were found, and marginally-significant associations of 1N with reduced E₂ and FSH were observed. Poor CYP2C19 and CYP2D6 metabolizers (GA and AA genotype carriers) showed a greater increase in DHEAS for detected versus undetected 1N compared with GG genotype carriers. Poor CYP2D6 metabolizers (1846 GA and AA genotypes) evidenced increased cortisol for detected versus undetected ETU.

CONCLUSIONS

The associations observed between urinary pesticide metabolites and altered thyroid and reproductive hormones are novel and should be verified in studies with larger sample size. Further research on gene-environment interactions is warranted to establish individual susceptibility to pesticides and the risk of adverse health effects.

Effect of Nigella sativa and Foeniculum vulgare seeds extracts on male mice exposed to carbendazim

The increasing prevalence of environmental pollutants such as pesticides is a major global problem that affects living organisms. Exposure to environmental pollutants remains a major source of health risk throughout the world. The potential health benefits of various medicinal plants and natural products in relation to protect various diseases are currently receiving considerable attention. A current approach is to develop a new biological compound from natural products that inhibits pain. Ethnopharmacological surveys have been found to be one of the most reliable tools for the discovery of the natural and semi-synthetic drug. The present study was performed to investigate the hematological and biochemical changes induced by carbendazim (CBZ) and the potential protective effect of seeds extracts of Nigella sativa (NSSE) and Foeniculum vulgare (FVSE) against CBZ toxicity in male mice. Mice were distributed into 6 groups. Mice of group 1 were served as control. Group 2 was exposed to CBZ. Group 3 was supplemented with NSSE and exposed to CBZ. Group 4 was treated with FVSE and CBZ. Normal mice of group 5 and 6 were subjected to NSSE and FVSE respectively. Body weight gain was significantly decreased in mice of group 2. In mice of group 2, significant declines of RBC, HB, Hct, WBC, total protein, FSH, LH, testosterone, T4, T3, CAT and SOD were observed. Moreover, the levels of ALT, AST, ALP, total bilirubin, creatinine, BUN, uric acid, glucose, cholesterol, CK, LDH, MDA and GSH were significantly enhanced. Treatment with NSSE and FVSE showed attenuation effects against CBZ induced hematological and biochemical changes. The results suggest that the attenuation effects of NSSE and FVSE attributed to their antioxidant properties.

The possible ameliorative effect of Olea europaea L. oil against deltamethrin-induced oxidative stress and alterations of serum concentrations of thyroid and reproductive hormones in adult female rats

This study aimed to verify whether Olea europaea L. (olive) oil (OEO) exerted a protective effect against oxidative stress induced by deltamethrin (DM) and alterations of pituitary, thyroid and gonadal hormones in adult female rats. DM (0,00256 g/kg body weight),OEO (0,6 g/kg body weight) and DM with OEO were administered to rats orally for 28 days. Volatile compounds present in olive oil were analysed by GC-MS. Estradiol (E₂), Thyroxine (T4),Thyroid Stimulating Hormone (TSH), Triiodothyronine (T3), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Progesterone (Pg) were measured in serum using Chemiluminescent Microparticle Immunoassay (CMIA). Lipid peroxidation (LPO), protein carbonyls (PCs), reduced glutathione (GSH) levels along with superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were determined in thyroid and ovarian tissues. Sesquiterpenes, (E,E)-α-farnesene (16.45%) and α-copaene (9,86%), were analysed as the main volatile compounds of OEO. The relative weight of ovaries and thyroid and body weight significantly decreased in rats treated with DM. DM caused significant alterations in TSH, T4, FSH, Pg and E₂ levels while T3 and LH concentrations remained unchanged when compared to control. DM also increased significantly LPO and PCs levels. In addition, GSH reserves as well as CAT, GPx, SOD and GST activities were suppressed in DM-received rats. The presence of OEO with DM returned the levels of oxidative stress markers, thyroid and reproductive hormones at the control values. Our results indicate that OEO is a powerful agent able to protect against DM oxidative stress and endocrine changes.

Thyroid-disrupting chemicals and brain development: an update

This review covers recent findings on the main categories of thyroid hormone-disrupting chemicals and their effects on brain development. We draw mostly on epidemiological and experimental data published in the last decade. For each chemical class considered, we deal with not only the thyroid hormone-disrupting effects but also briefly mention the main mechanisms by which the same chemicals could modify estrogen and/or androgen signalling, thereby exacerbating adverse effects on endocrine-dependent developmental programmes. Further, we emphasize recent data showing how maternal thyroid hormone signalling during early pregnancy affects not only offspring IQ, but also neurodevelopmental disease risk. These recent findings add to established knowledge on the crucial importance of iodine and thyroid hormone for optimal brain development. We propose that prenatal exposure to mixtures of thyroid hormone-disrupting chemicals provides a plausible biological mechanism contributing to current increases in the incidence of neurodevelopmental disease and IQ loss.

Selenium nanoparticles prevents lead acetate-induced hypothyroidism and oxidative damage of thyroid tissues in male rats through modulation of selenoenzymes and suppression of miR-224

Selenium nanoparticles (Se-NPs) are customizable drug delivery vehicles that show good bioavailability, higher efficacy and lower toxicity than ordinary Se. Pre-treatment of male rats with these NPs has been recently shown to exert a protective effect against chromium-induced thyroid dysfunction. This study, therefore, aimed to investigate and characterize the potential protective mechanism of Se-NPs against lead (Pb) acetate-induced thyrotoxicity. We found that prophylactic and concurrent treatment of Pb acetate-exposed rats with Nano-Se (0.5 mg/kg, i.p) for 15 wk significantly alleviated the decrease in free triiodothyronine (fT3) and free thyroxine (fT4) levels as well as fT3/fT4 ratio% and the increase in thyroid stimulating hormone (TSH) levels to approach control values. This was accompanied by a reduction in the accumulation of Pb in serum and thyroid tissues as well as maintenance of thyroidal pro-oxidant/antioxidant balance and iodothyronine deiodinase type 1 (ID1), an essential enzyme for metabolizing of T4 into active T3, gene expression. Surprisingly, miR-224, a direct complementary target of ID1 mRNA, expression in the thyroid tissues was significantly down-regulated in Nano-Se-pre- and co-treated Pb acetate intoxicated animals. Such changes in miR-224 expression were negatively correlated with the changes in ID1 gene expression and serum fT3 level. These results suggest that Se-NPs can rescue from Pb-induced impairment of thyroid function through the maintenance of selenoproteins and down-regulation of miR-224.

mTOR inhibition by rapamycin protects against deltamethrin-induced apoptosis in PC12 Cells

The autophagy pathway can be induced and upregulated in response to intracellular reactive oxygen species (ROS). In this study, we explored a novel pharmacotherapeutic approach involving the regulation of autophagy to prevent deltamethrin (DLM) neurotoxicity. We found that DLM-induced apoptosis in PC12 cells, as demonstrated by the activation of caspase-3 and -9 and by nuclear condensation. DLM treatment significantly decreased dopamine (DA) levels in PC12 cells. In addition, we observed that cells treated with DLM underwent autophagic cell death, by monitoring the expression of LC3-II, p62, and Beclin-1. Exposure of PC12 cells to DLM led to the production of ROS. Treatment with N-acetyl cysteine (NAC) effectively blocked both apoptosis and autophagy. In addition, mitogen-activated protein kinase (MAPK) inhibitors attenuated apoptosis as well as autophagic cell death. We also investigated the modulation of DLM-induced apoptosis in response to autophagy regulation. Pretreatment with the autophagy inducer, rapamycin, significantly enhanced the viability of DLM-exposed cells, and this enhancement of cell viability was partially due to alleviation of DLM-induced apoptosis via a decrease in levels of cleaved caspase-3. However, pretreatment of cells with the autophagy inhibitor, 3-methyladenine (3MA), significantly increased DLM toxicity in these cells. Our results suggest that DLM-induced cytotoxicity is modified by autophagy regulation and that rapamycin protects against DLM-induced apoptosis by enhancing autophagy. Pharmacologic induction of autophagy by rapamycin may be a useful treatment strategy in neurodegenerative disorders. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 109-121, 2017.

PPAR-γ activation attenuates deltamethrin-induced apoptosis by regulating cytosolic PINK1 and inhibiting mitochondrial dysfunction

Central events in the mitochondrial-dependent cell death pathway include the disruption of mitochondrial membrane potential, which causes the release of apoptogenic molecules leading to cell death. Based on the cytotoxic mechanism of deltamethrin (DLM), we examined the neuroprotective mechanisms of rosiglitazone (RGZ), which is against DLM-induced neuronal cell death. In this study, we found that DLM induces apoptosis in SH-SY5Y cells as demonstrated by the activation of caspase-3 and nuclear condensation. In addition, neuronal cell death in response to DLM was due to mitochondrial dependent-apoptosis pathways since DLM increased cytochrome c release into the cytosol and activated caspase-9. DLM exposure reduced PINK1 expression, and pretreatment with RGZ significantly reduced cytochrome c release and caspase-9 activation. RGZ also attenuated the reduction of complex I activity, mitochondrial membrane potential, and ATP levels. Pretreatment with RGZ significantly enhanced PINK1 expression in DLM-exposed cells. In addition, RGZ increased cytosolic PINK1 by inhibiting mitochondrial translocation of PINK1. Interestingly, RGZ fails to rescue DLM-induced mitochondrial dysfunction both in PINK1 knockdown and PPAR-γ antagonist treated cells. Results from this study suggest that RGZ exerts anti-apoptotic effects against DLM-induced cytotoxicity by attenuation of mitochondrial dysfunction through cytosolic PINK1-dependent signaling pathways.

Exposure to non-persistent pesticides and thyroid function: A systematic review of epidemiological evidence

Numerous pesticides are recognized for their endocrine-disrupting properties. Non-persistent pesticides such as organophosphates, dithiocarbamates and pyrethroids may interfere with thyroid function as suggested by animal studies. However, the influence of chronic exposure to these compounds on thyroidal functions in humans remains to be determined. The present study aimed to review epidemiological evidence for an association between exposure to non-persistent pesticides and circulating levels of thyroid hormones (thyroxin [T4] and triiodothyronine [T3]) and thyroid-stimulating hormone (TSH). A systematic review was conducted using MEDLINE, SCOPUS and Virtual Health Library (BVS) databases. Articles were limited to original studies and reports published in English, Portuguese or Spanish. Nineteen epidemiological studies were identified, 17 of which were cross-sectional, 14 were of occupationally exposed workers and 11 used exposure biomarkers. Fungicides and organophosphates (OP) insecticides were the most studied pesticides. Although methodological heterogeneity between studies was noted, particularly regarding study design, exposure assessment, and control of confounding, most of them showed associations with changes in T3 and T4, and/or TSH levels, while results from a few of these are consistent with experimental data supporting the findings that non-persistent pesticide exposure exerts hypothyroid-like effects. However, reporting quality was moderate to poor in 50% of the studies, particularly regarding method of selection of participants and discussion of external validity. Overall, current knowledge regarding the impact of non-persistent pesticides on human thyroid function is still limited. Given the widespread use of pesticides, future research should assess effects of exposure to currently-used pesticides in cohort studies combining comprehensive questionnaire-based assessment and biomarkers. Investigators need to pay particular attention to exposure during critical windows of brain development and exposure in agricultural populations.

The ameliorating effects of vitamin E on hepatic antioxidant system and xenobiotic-metabolizing enzymes in fenvalerate-exposed iodine-deficient rats

This study investigated the effects of vitamin E (VE) on hepatic antioxidant system and drug-metabolizing enzymes in fenvalerate (FEN)-exposed iodine-deficient (ID) Wistar rats. ID was produced by perchlorate containing drinking water. VE was introduced by a loading dose of 100 mg/kg/d, i.g. for the first three days in the last week of feeding period; then with a single maintenance dose of 40 mg/kg on the 4th day. During last week, FEN groups (F) received 100 mg/kg/d, i.p. FEN. VE alone did not significantly affect thyroid hormones and antioxidant parameters; however, significantly increased total cytochrome P450 (38%) and cytochrome b5 levels (36%). In all ID groups, plasma thyroid-stimulating hormone (TSH) levels increased markedly, but remained at control level in vitamin E plus FEN receiving iodine-deficient group (IDVF) group. Glutathione peroxidase activity showed marked increases in F (19%) and FEN-exposed iodine-deficient group (IDF, 48%) groups. FEN treatment significantly increased total cytochrome P450 (28%) and thiobarbituric acid reactive substance levels (36%), as well as 7-ethoxyresorufin O-deethylase (120%), 7-penthoxyresorufin O-deethylase (139%) and glutathione S-transferase (15%) activities and decreased total glutathione concentrations (28%) versus control. Overall results suggest that vitamin E has ameliorating effects on the measured parameters in ID and/or FEN exposure.

Monitoring of deiodinase deficiency based on transcriptomic responses in SH-SY5Y cells

Iodothyronine deiodinase types I, II, and III (D1, D2, and D3, respectively), which constitute a family of selenoenzymes, activate and inactivate thyroid hormones through the removal of specific iodine moieties from thyroxine and its derivatives. These enzymes are important in the biological effects mediated by thyroid hormones. The expression of activating and inactivating deiodinases plays a critical role in a number of cell systems, including the neuronal system, during development as well as in adult vertebrates. To investigate deiodinase-disrupting chemicals based on transcriptomic responses, we examined differences in gene expression profiles between T3-treated and deiodinase-knockdown SH-SY5Y cells using microarray analysis and quantitative real-time RT-PCR. A total of 1,558 genes, consisting of 755 upregulated and 803 downregulated genes, were differentially expressed between the T3-treated and deiodinase-knockdown cells. The expression levels of 10 of these genes (ID2, ID3, CCL2, TBX3, TGOLN2, C1orf71, ZNF676, GULP1, KLF9, and ITGB5) were altered by deiodinase-disrupting chemicals (2,3,7,8-tetrachlorodibenzo-p-dioxin, polychlorinated biphenyls, propylthiouracil, iodoacetic acid, methylmercury, β-estradiol, methimazole, 3-methylcholanthrene, aminotriazole, amiodarone, cadmium chloride, dimethoate, fenvalerate, octylmethoxycinnamate, iopanoic acid, methoxychlor, and 4-methylbenzylidene-camphor). These genes are potential biomarkers for detecting deiodinase deficiency and predicting their effects on thyroid hormone production.

Oxidative stress, hematological and biochemical alterations in farmers exposed to pesticides

In this study, a cohort of farmers from the Mateur region in the North of Tunisia, were interviewed and examined for the biochemical effects of pesticides. We studied their haematological profile, lipid parameters, serum markers of nephrotoxicity and hepatotoxicity. We also evaluated the activities of Butyrylcholinesterase (BChE), Acetylcholinesterase (AChE) and thiolactonase-paroxonase (PON). Moreover, lipid peroxidation and activities of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were determined. The duration of pesticide use and the farmers' age were considered in the analysis. Our results revealed significant differences in some haematological parameters, in liver and kidney functions, in the lipidic status of the pesticide-exposed group. We also reported an increase in the index of incidence of cardiovascular risk in farmer populations. A significant decrease in AChE, BChE and PON levels was found among farmers. Lipid peroxidation, however, increased. The activities of SOD and CAT were remarkably elevated in farmer populations. There was a significant relation between changes in biological markers, the duration of pesticide use and the farmers' age. This study indicates that a long-term exposure to pesticides may play an important role in the development of vascular diseases via metabolic disorders of lipoproteins, lipid peroxidation and oxidative stress, inhibition of BChE and decrease in thiolactonase-PON levels.

Protective effect of naringenin against lead-induced oxidative stress in rats

Oxidative stress is thought to be involved in lead-induced toxicity. The aim of this study was to investigate the possible protective role of naringenin on lead-induced oxidative stress in the liver and kidney of rats. In the present investigation, lead acetate (500 mg Pb/L) was administered orally for 8 weeks to induce hepatotoxicity and nephrotoxicity. The levels of hepatic and renal markers such as alanine aminotransferase, aspartate aminotransferase, urea, uric acid, and creatinine were significantly (P < 0.05) increased following lead acetate administration. Lead-induced oxidative stress in liver and kidney tissue was indicated by a significant (P < 0.05) increase in the level of maleic dialdehyde and decreased levels of reduced glutathione, superoxide dismutase, catalase, and glutathione peroxidase. Naringenin markedly attenuated lead-induced biochemical alterations in serum, liver, and kidney tissues (P < 0.05). The present study suggests that naringenin shows antioxidant activity and plays a protective role against lead-induced oxidative damage in the liver and kidney of rats.

Effect of continuous inhalation of allethrin-based mosquito coil smoke in the male reproductive tract of rats

OBJECTIVES

Continuous inhalation of allethrin-based mosquito coil smoke may affect fertility, an aspect that has not received much attention. In this study, we attempt to understand the harmful effects on the male reproductive system caused by continuous exposure to allethrin-based mosquito coil smoke.

METHODS

Adult Wistar rats were allowed to inhale mosquito coil smoke for 15-180 days, and male reproductive tract tissues (caput, cauda, and testes) were collected. Using standard biochemical techniques, changes in oxidative stress (lipid peroxidation) and antioxidant status was measured. Histopathological analyses were carried out to assess pathomorphological damage in the caput, cauda, and testis. Real-time polymerase chain reaction was carried out to determine the expression pattern of the stress-response gene, p53, and the spermatogenic factors c-Kit, Scf, and Tgf-β1.

RESULTS

In rats exposed to allethrin-based mosquito coil smoke for 15-180 days, compared to the unexposed controls, lipid peroxidation was increased in the cauda and testes. The activity of antioxidant enzymes remained largely unchanged in the all the tissues analyzed. Histopathological analyses revealed loss of tubule architecture, epithelial cell disruption, increase in lumen size, interstitial edema, and presence of dead spermatozoa. p53 gene expression was differentially altered in the epididymis and testes. The expression of spermatogenic factors, namely, stem cell factor and its ligand c-Kit was unaltered though decreased levels of Tgf-β1 were observed.

CONCLUSION

Results of this study demonstrate that prolonged exposure to allethrin-based mosquito coil smoke could lead to oxidative stress and compromise germ cell production.

Fenvalerate induced hepatic oxidative stress in selenium- and/or iodine-deficient rats

Considering the potential adverse effects of selenium and iodine deficiencies, and frequency of intensive but improper use of insecticides, this study was designed to evaluate the effects of a pyrethroid insecticide, fenvalerate, on the oxidant/antioxidant status of liver using a rat model of iodine and/or selenium deficiency. The study was conducted on eight groups of 3-week old Wistar rats. Iodine and/or selenium deficiency was introduced by feeding the animals with a diet containing <0.005 mg selenium/kg and/or supplying with 1% sodium perchlorate containing drinking water for a period of 7 weeks. Fenvalerate exposure (100 mg/kg/d, i.p., for the last 7 days) in normal rats increased hepatic glutathione peroxidase activity and lipid peroxidation, decreased glutathione content, but did not change the activities of catalase or any of the superoxide dismutase forms; in iodine-deficient animals caused only the elevation of lipid peroxidation; in selenium-deficient animals and in combined iodine/selenium deficiency decreased glutathione peroxidase, increased catalase activities and lipid peroxidation, and decreased all the forms of superoxide dismutase activity only in combined deficiency. These results suggested that fenvalerate is an oxidant stress inducer in rat liver, and its potential effects on pro-oxidant/antioxidant balance may also be important for human populations, particularly with iodine and/or selenium deficiencies.

Protective effect of curcumin on cypermethrin-induced oxidative stress in Wistar rats

The aim of present study was to investigate the protective effect of curcumin on cypermethrin-induced changes in blood biochemical markers and tissue antioxidant enzyme in rats. Rats were divided into six groups of six each: group I used as control and II and III groups were used as vehicle control. While, groups IV, V and VI were orally treated with curcumin (100 mg/kg body weight), cypermethrin (25 mg/kg body weight) and cypermethrin plus curcumin, respectively for 28 days. Serum biochemical markers were measured in the serum, and the levels of lipid peroxidation and antioxidant enzyme activity were determined in the liver, kidney and brain. Cypermethrin administration caused elevated level of blood biochemical markers in serum and lipid peroxidation in liver, kidney and brain. While the activities of non-enzymatic and enzymatic antioxidants levels were decreased except superoxide dismutase in liver, kidney and brain tissues. The presence of curcumin with cypermethrin significantly decreased the blood biochemical markers and lipid peroxidation but significantly increased the reduced glutathione, catalase and glutathione peroxidase level and preserved the normal histological architecture of the liver, kidney and brain. Our results indicate that curcumin can be potent protective agent against cypermethrin-induced biochemical alterations and oxidative damage in rats.

Fenvalerate exposure alters thyroid hormone status in selenium- and/or iodine-deficient rats

Considering the potential adverse effects of selenium and iodine deficiencies, and taking into account the widespread but often careless use of pyrethroid insecticides and their possible endocrine-disrupting effects, this study was undertaken to investigate the effects of fenvalerate on thyroid hormone parameters in both healthy and selenium- and/or iodine-deficient rats. Fenvalerate exposure had no effect on the TT4 levels of healthy controls but caused significant increases both in iodine deficiency (ID) and selenium plus iodine deficiency (ISeD), and a significant decrease in selenium deficiency (SeD). Dramatic increases in TT3 of all groups were observed by fenvalerate. Moreover, it caused insignificant decrease of thyroid stimulating hormone in healthy controls, no effect in SeD, and significant elevation in ID and ISeD. These results, thus, showed that the widely used pyrethroid insecticide fenvalerate has the potential to change significantly thyroid hormone parameters both in normal and deficiency states, and consequences of its thyroid status modifying effect might be of critical importance particularly in sensitive individuals and patients with thyroid dysfunction.

Protective Role of Tinospora cordifolia against Lead-induced Hepatotoxicity

The importance of Tinospora cordifolia stem and leaves extract was investigated for its possible hepatoprotective effect in Swiss albino male mice against lead nitrate induced toxicity. Oral administration of plant extracts prevented the occurrence of lead nitrate induced liver damage. The decreased level of tissue enzymes, i.e., superoxide dismutase (SOD), catalase (CAT) and increased level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and acid phosphatase (ACP) were observed in mice treated with lead. Administration of aqueous stem extract (400 mg/kg body weight, orally) and aqueous leaves extract (400 mg/kg body weight, orally) along with the lead nitrate (5 mg/kg body weight, i.p. for 30 days) increased the activities of SOD and CAT and decreased the levels of AST, ALT, ALP, and ACP enzymes in mice. These biochemical observations were supplemented by histopathology/histological examinations of liver section. Results of this study revealed that plant extract could afford protection against lead-induced hepatic damage.

Protective effect of Aquilegia vulgaris (L.) against lead acetate-induced oxidative stress in rats

Oxidative stress has been proposed as a possible mechanism involved in lead toxicity. The current study was carried out to evaluate the antioxidant activity of the ethanol extract of Aquilegia vulgaris (L.) against lead acetate (LA)-induced oxidative stress in male rats. Tested animals were treated orally with A. vulgaris extract (100 ppm) in combination with, before, or after LA treatment (20 ppm). The results indicated that the extract alone did not induce any significant changes in body weight gain, food intake, serum biochemical chemistry or the histological picture of the liver and kidney. However, it increased significantly the level of Glutathione (GSH). On the other hand, LA decreased food intake, body weight gain and induced oxidative stress as indicated by the significant changes in serum biochemical parameters and histological picture of liver and kidney and increased lipid peroxide and reduces GSH levels in liver tissues. The extract succeeded to improve the histological pictures of liver and kidney and the biochemical parameters towards the normal values of the control. Moreover, this improvement was pronounced in the animals treated with the extract after LA intoxication.

NF-E2 Related Factor 2 Activation and Heme Oxygenase-1 Induction by tert-Butylhydroquinone Protect against Deltamethrin-Mediated Oxidative Stress in PC12 Cells

Recent findings suggest that oxidative stress caused by pyrethroid pesticides could be closely involved in the neurotoxicity. tert-Butylhydroquinone ( tBHQ) is a known inducer of Nrf2-mediated transcription, and treatment of cells with tBHQ can confer protection against H 2O 2 and 6-hydroxydopamine (6-OHDA). In this study, we investigated the neuroprotective effect of tBHQ against deltamethrin (DM)-induced oxidative stress using rat PC12 adrenal pheochromocytoma cells. The pretreatment of PC12 cells with tBHQ significantly reduced DM-induced generation of reactive oxygen species (ROS) and increased intracellular ionized calcium ([Ca (2+)] i). We also observed that DM or tBHQ induced the expression of NF-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), a Nrf2-regulated gene. In addition, the Nrf2 antioxidant responsive element (ARE) pathways activated by tBHQ caused a partial inhibition of the DM-induced Nrf2 and HO-1 expression. Altogether, our data clearly indicate that an activation of Nrf2/ARE pathways in PC12 cells by tBHQ treatment protects cells from DM-induced oxidative stress and regulates DM- mediated adaptive responses in PC12 cells via translocation of Nrf2.

ANTIHYPERGLYCAEMIC AND ANTIPEROXIDATIVE ROLES OF ACARBOSE IN TYPE 2 DIABETES MELLITUS ARE POSSIBLY MEDIATED THROUGH CHANGES IN THYROID FUNCTION

1. The aim of the present study was to reveal the possible involvement of thyroid hormones in the antihyperglycaemic and antiperoxidative effects of acarbose. 2. The effects of acarbose on changes in serum concentration of thyroid hormones, insulin and glucose in dexamethasone-induced type 2 diabetic mice were investigated. Simultaneously, changes in lipid peroxidation (LPO), reduced glutathione (GSH) content and the activity of associated endogenous anti-oxidant enzymes, such as superoxide dismuatase (SOD) and catalase (CAT), were investigated in renal and cardiac tissues, which are commonly affected in diabetes mellitus. 3. Although administration of dexamethasone (1.0 mg/kg, i.m., for 22 days) caused hyperglycaemia with a parallel increase in serum insulin and tissue LPO, it decreased thyroid hormone concentrations and the activity of SOD and CAT. 4. When dexamethasone-induced hyperglycaemic mice were treated with acarbose (10 mg/kg per day, p.o., for 15 days), levels of thyroid hormones were increased and most of the abnormalities, including serum insulin and glucose levels, tissue LPO, SOD and CAT activity and GSH content, were reversed. 5. These findings suggest the involvement of thyroid hormones in the mode of action of acarbose in amelioration of type 2 diabetes mellitus.

CAR and PXR: xenosensors of endocrine disrupters?

The pregnane X-receptor (PXR) and the constitutive androstane receptor (CAR) are orphan nuclear receptors activated by a variety of ligands. Currently it remains uncertain whether these receptors have a high-affinity ligand or instead function as more generalized steroid/xenobiotic sensors. Both receptors are important regulators of several steroid and xenobiotic detoxification enzymes and transporters (phases I-III) in the liver and intestine and thus are important regulators of adaptation to chemical stress. The detoxification proteins induced are responsible for the metabolism, deactivation and transport of bile acids, thyroid and steroid hormones, numerous environmental chemicals, and several drugs. PXR and CAR received their names because of steroid ligands that activate and inhibit their transcriptional activity, respectively. Interestingly, some steroids and steroid mimics activate one or both receptors, including several endocrine disrupting chemicals. Environmental estrogens, such as the pesticides methoxychlor, endosulfan, dieldrin, DDT, and the plasticizer nonylphenol activate either PXR or both PXR and CAR. Because PXR and CAR are activated by numerous steroids and endocrine disrupters, it appears that these receptors protect the integrity of the endocrine system. They recognize an increase in steroid-like chemicals and, in turn, induce detoxification. Furthermore, PXR and CAR induce enzymes, such as the CYP2B and CYP3A family members, responsible for the metabolism of steroid and thyroid hormones and this may alter their normal physiological function. This review summarizes the available data on the activity of endocrine disrupters and endocrine active chemicals on PXR and CAR, examines the role of PXR and CAR in protection from these chemicals, and evaluates potential adverse physiological consequences of PXR and CAR activation.

Combined efficacies of lipoic acid and 2,3-dimercaptosuccinic acid against lead-induced lipid peroxidation in rat liver

Oxidative stress with subsequent lipid peroxidation has been postulated as one mechanism for lead toxicity. Hence in assessing the protective effects of lipoic acid (LA) and meso 2,3-dimercaptosuccinic acid (DMSA) on lead toxicity, they were tested either separately or in combination for their effects on selected indices of hepatic oxidative stress. Elevated levels of lipid peroxides were accompanied by altered antioxidant defense systems. Lead acetate (Pb - 0.2%) was administered in drinking water for five weeks to induce toxicity. LA (25 mg kg(-1) body wt. day(-1) i.p) and DMSA (20 mg kg(-1) body wt. day(-1) i.p) were administered individually and also in combination during the sixth week. Lead damage to the liver was evident in the decreases in hepatic enzymes alanine transaminase (-38%), aspartate transaminase (-42%) and alkaline phosphatase (-43%); increases in lipid peroxidation (+38%); decreases in the antioxidant enzymes catalase (-45%), superoxide dismutase (-40%), glutathione peroxidase (-46%) and decreases in glutathione (-43%) and decreases in glutathione metabolizing enzymes, glutathione reductase (-59%), glucose-6-phosphate dehydrogenase (-27%) and glutathione-S-transferase (-42%). In combination LA and DMSA completely ameliorated the lead induced oxidative damage. Either compound alone was however only partially protective against lead damage.

Protective role of melatonin and a combination of vitamin C and vitamin E on lung toxicity induced by chlorpyrifos-ethyl in rats

The ameliorating effects of melatonin and vitamin C plus vitamin E were examined histologically and biochemically in lung tissues in rats exposed to chlorpyriphos-ethyl (CE). Experimental groups were as follows: Control group (C), CE treated group (CE), vitamin C plus vitamin E treated group (Vit), melatonin treated group (Mel), vitamin C plus vitamin E plus CE treated group (Vit + CE), and melatonin plus CE treated group (Mel + CE). Vitamin E and vitamin C were administered intramuscularly at the rates of 150 and 200 mg per kg body weight, respectively, in Vit and Vit + CE groups, once a day for 6 consecutive days. Melatonin was administered intramuscularly at the rate of 10 mg per kg body weight in Mel and Mel + CE groups, once a day for 6 consecutive days. At the end of the fifth day, the rats of CE, Vit + CE and Mel + CE groups were treated orally with CE dissolved in corn oil with two equal doses of 41 mg CE per kg body weight at zero and twenty-first hours. Tissue samples of lungs were taken by using appropriate techniques for biochemical and histological examinations under anesthesia at the twenty-fourth hours of CE administration, at the end of the sixth day of the experiment. In tissue homogenates, the level of thiobarbituric acid reactive substances (TBARS), antioxidant potential (AOP), and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined. TBARS was significantly high (p < 0.05) in CE group compared to control group, while TBARS was found to significantly decrease (p < 0.05) with Vit and Mel groups compared to control. On the other hand, TBARS was seen to significantly decrease (p < 0.05) in both groups of Vit + CE and Mel + CE compared to CE group. In comparison with CE group, SOD activity was significantly high (p < 0.05) with the groups of Vit, Mel, Vit + CE and Mel + CE. GSH-Px activity was found to significantly decrease (p < 0.05) with CE group, compared with both C and Vit groups. AOP was significantly lower (p < 0.01) in CE group than C group. Although there was an increased AOP with Vit + CE and Mel + CE groups compared to CE group, the increase in AOP was only seen to be significant (p < 0.05) in Mel + CE group. In comparison with C group, AOP significantly (p < 0.05) increased with Vit group. There was also a significant (p < 0.05) increase in AOP with Mel + CE group, compared with CE group. Additionally, AOP was significantly lower (p < 0.05) in Vit + CE group than Mel + CE group. Lungs were examined histologically at the end of sixth day. There were remarkable changes in the histomorphology of peribronchial and perivascular area in the lung of rats treated with CE. These were infiltration of mononuclear cells (such as lymphocytes, plasmocytes, macrophages), hyperplasia of type II pneumocyte, and thickened and increased connective tissue. Damage to the lung tissue such as increased inflammatory mononuclear cells in peribronchial and perivascular areas were more pronounced for the CE group than Vit + CE and Mel + CE groups in which these changes were higher than C, Vit and Mel groups. These results suggest that CE increases lipid peroxidation and decreases antioxidant enzymes activities and AOP due to increasing oxidative stress induced by CE, and high doses of vitamin C plus vitamin E and melatonin considerably reduce CE toxicity in lung tissues of rats.

Cypermethrin-induced plasma membrane perturbation on erythrocytes from rats: reduction of fluidity in the hydrophobic core and in glutathione peroxidase activity

The effects of treatment with the synthetic insecticide cypermethrin on plasma membrane fluidity, lipid peroxidation and antioxidant status in rat erythrocytes were investigated. Rats were treated by gavage with a low dose (12.5 mg/kg body weight per day) of cypermethrin in corn oil for 60 days. DPH and TMA-DPH fluorescence anisotropy experiments show that cypermethrin treatment, compared with controls, induced a significant decrease in erythrocyte membrane fluidity measured by DPH, while no changes were observed using TMA-DPH. Cypermethrin treatment also induced a significant increase in the lipid peroxidation, measured by the formation of conjugated dienes. The increased oxidative stress resulted in a significant decrease in the activity of glutathione peroxidase. The results are discussed in terms of preferential localization of cypermethrin in the hydrophobic core of the membrane, where it increases lipid packing and consequently decreases membrane fluidity.

Plasma and RBCs antioxidant status in occupational male pesticide sprayers

A total of forty-one (n=41) male, healthy agricultural sprayers, exposed to pesticides for 5 years, were compared with twenty one (n=21) controls matched for age and economic status with respect to free radical generation, lipid peroxidation, antioxidant status and concentration of cellular enzymes were determined. Significantly increased TBARS (thiobarbituric acid reactive substances) were observed (P<0.001) in sprayer populations when compared to controls. The concentration of antioxidants such as glutathione (GSH), alpha-tocopherol, ascorbic acid and ceruloplasmin were significantly altered when compared to controls, and the activities of antioxidant enzymes were remarkably elevated (P<0.001) in sprayer populations, when compared to controls.

Glutathione S-transferases as antioxidant defence agents confer pyrethroid resistance in Nilaparvata lugens

Selection of a laboratory colony of the brown planthopper Nilaparvata lugens with the pyrethroids permethrin and lambda-cyhalothrin increased its resistance to both insecticides. Biochemical analysis and synergistic studies with metabolic inhibitors indicated that elevated glutathione S-transferases (GSTs) with a predominant peroxidase activity conferred resistance to both pyrethroids, whereas esterases conferred part of the resistance to permethrin. Purified esterases hydrolysed permethrin at a slow rate, but incubation of either pyrethroid or their primary metabolites with partially purified GSTs had no effect on the metabolic profile. Although GSTs were sensitive to inhibition by both pyrethroids, they did not serve as binding proteins, as previously hypothesized [Grant and Matsumura (1988) Insect Biochem. 18, 615-622]. We demonstrate that pyrethroids, in addition to their neurotoxic effect, induce oxidative stress and lipid peroxidation in insects. Pyrethroid exposure induced lipid peroxides, protein oxidation and depleted reduced glutathione. Elevated GSTs in the resistant strains attenuated the pyrethroid-induced lipid peroxidation and reduced mortality, whereas their in vivo inhibition eliminated their protective role. We therefore hypothesize that the main role of elevated GSTs in conferring resistance in N. lugens is through protecting tissues from oxidative damage. Our study extends the GSTs' range of efficacy to pyrethroid insecticides and possibly explains the role of elevated GSTs in other pyrethroid-resistant insects.

Achyranthes aspera elevates thyroid hormone levels and decreases hepatic lipid peroxidation in male rats

A study was made to evaluate the role of Achyranthes aspera on the changes in serum thyroid hormone concentrations and glucose levels in male rats. An attempt was also made to establish the relationship between hepatic lipid peroxidation and extract induced changes in thyroid hormone concentration, if any. Adult male Wistar rats were orally administered with the aqueous leaf extract of Achyranthes aspera at a dose of 200 mg/kg b. wt./day for 7 days. The effects of the extract on body weight, hepatic protein content, lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activities and on serum triiodothyronine (T3), thyroxine (T4) and glucose levels were evaluated. The extract exhibited significant prothyroidic activity as it enhanced the levels of both the thyroid hormones along with an increase in serum glucose concentration, body weight and hepatic protein content. On the other hand, it decreased hepatic LPO without altering the activities of the two antioxidant enzymes, SOD and CAT significantly, suggesting a direct free radical scavenging activity of the extract. It appears that the Achyranthes aspera leaf extract is both prothyroidic and antiperoxidative in nature.

Withania somnifera root extract in the regulation of lead-induced oxidative damage in male mouse

The importance of Withania somnifera root extract in the regulation of lead toxicity with special reference to lipid peroxidative process has been investigated in liver and kidney tissues. While lead treatment (0.5 mg kg(-1)body wt. day(-1)for 20 days) enhanced hepatic and renal lipid peroxidation (LPO), administration of plant extract in the doses of 0.7 g kg(-1)and 1.4 g kg(-1)body wt. day(-1)along with equivalent doses of lead acetate for 20 days significantly decreased LPO and increased the activities of antioxidant enzymes, viz., superoxide dismutase (SOD) and catalase (CAT), thus retaining normal peroxidative status of the tissues. We suggest that the ameliorating role of root extract of W. somnifera in the lead intoxicated mice could be the result of its antiperoxidative action.

Role of Moringa oleifera leaf extract in the regulation of thyroid hormone status in adult male and female rats

The role of Moringa oleifera aqueous leaf extract in the regulation of thyroid hormone status, was studied in adult Swiss rats. Other than the thyroid hormone concentrations, hepatic lipid peroxidation (LPO) and the activities of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) were evaluated. In the first experiment, effects of the leaf extract (175 mg kg(-1)body wt. day(-1)for 10 days) were studied both in male and female animals. Following the administration of the extract, serum triiodothyronine (T(3)) concentration and hepatic LPO decreased with a concomitant increase in the serum thyroxine (T(4)) concentration, in female rats, while in males no significant changes were observed, suggesting that Moringa oleifera leaf extract is more effective in females than in the males. To evaluate the impact of a higher dose, in the second experiment, the study was repeated in female rats, with 350 mg kg(-1)body wt. day(-1)for the same duration. Almost similar reduction in the serum T(3)concentration (approx. 30%) and an increase in the T(4)concentration were observed suggesting the inhibiting nature of Moringa oleifera leaf extract in the peripheral conversion of T(4)to T(3), the principal source of the generation of latter hormone. As the antiperoxidative effects were exhibited only by the lower dose and percent decrease in T(3)concentration was nearly the same by both the doses, it is suggested that the lower concentration of this plant extract may be used for the regulation of hyperthyriodism. 2000 Academic Press@p$hr

Inhibition of triiodothyronine production by fenugreek seed extract in mice and rats

The effects of fenugreek seed extract on the alterations in serum thyroid hormone concentrations were studied in adult male mice and rats. Simultaneously, hepatic lipid peroxidation (LPO) and the activities of the antioxidant enzymes, viz superoxide dismutase (SOD) and catalase (CAT) were examined. Administration of methi seed extract (0.11 g kg body wt.(-1) day(-1) for 15 days) to both mice and rats significantly decreases serum triiodothyronine (T(3)) concentration and T(3)/T(4) ratio, but increases thyroxine (T(4)) levels and body weight. While hepatic LPO and CAT activities were not altered, a significant decrease in SOD activity was observed in both the animal models. These findings suggest that fenugreek seed extract induced inhibition in T(4)to T(3) conversion is not peroxidation-mediated and the inhibition in SOD activity could be the result of a decrease in the protein anabolic hormone, T3.

Gugulu (Commiphora mukul) induces triiodothyronine production: possible involvement of lipid peroxidation

An investigation was made to find out the importance of gugulu (Commiphora mukul) in thyroid function of mice and to reveal the possible involvement of lipid peroxidation (LPO), if any. While no marked change in the concentrations of serum thyroxine (T4) was observed, triiodoth yronine (T3) concentration and T3/T4 ratio were enhanced following the administration of gugulu extract (0.2 g/kg b. wt./d for 15 days). A concomitant decrease in LPO was also noticed in liver, the principal site of T3 generation, suggesting that gugulu induced increase in T3 concentration is LPO mediated.

Lipid peroxidative damage on pyrethroid exposure and alterations in antioxidant status in rat erythrocytes: a possible involvement of reactive oxygen species

Pyrethroid pesticides are used preferably over organochlorines and organophosphates due to their high effectiveness, low toxicity to non-target organisms and easy biodegradibility. However, it is possible that during the pyrethroid metabolism, there is generation of reactive oxygen species (ROS) and pyrethroids may produce oxidative stress in intoxicated rats. The present study was therefore, undertaken to determine pyrethroid-induced lipid peroxidation (LPO) and to show whether pyrethroid intoxication alters the antioxidant system in erythrocytes. A single dose of cypermethrin and/or fenvalerate (0.001% LD50) was administered orally to rats and the animals were sacrificed at 0, 1, 3, 7 and 14 days of treatment. The results showed that lipid peroxidation (LPO) in erythrocytes increased within 3 days of pyrethroid treatment. The increased oxidative stress resulted in an increase in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). The increase in reduced glutathione (GSH) content in erythrocytes may probably be an initial adaptive response to increased oxidative stress in pyrethroid intoxicated rats. Erythrocytes and serum acetylcholinesterase (AChE) activity was measured in pyrethroid-induced oxidative stress as it may mimic inhibition in target tissues such as muscle and brain. The inhibition in erythrocytes and serum AChE activity was partially relieved over a period of time indicating recovery from pyrethroid intoxication. The increase in erythrocyte LPO correlated with the inhibition in erythrocyte AChE activity and so erythrocyte AChE can be a marker enzyme in pyrethroid toxicity. The results show oxidative stress and alteration in antioxidant enzymes in erythrocytes of pyrethroid intoxicated rats.

Endocrine, immune, and behavioral effects of aldicarb (carbamate), atrazine (triazine) and nitrate (fertilizer) mixtures at groundwater concentrations

This paper describes the results of 5 years of research on interactive effects of mixtures of aldicarb, atrazine, and nitrate on endocrine, immune, and nervous system function. The concentrations of chemicals used were the same order of magnitude as current maximum contaminant levels (MCLs) for all three compounds. Such levels occur in groundwater across the United States. Dosing was through voluntary consumption of drinking water. We used fractional and full factorial designs with center replicates to determine multifactor effects. We used chronic doses in experiments that varied in duration from 22 to 103 days. We tested for changes in thyroid hormone levels, ability to make antibodies to foreign proteins, and aggression in wild deer mice, Peromyscus maniculatus, and white outbred Swiss Webster mice, Mus musculus, ND4 strain. Endocrine, immune, and behavior changes occurred due to doses of mixtures, but rarely due to single compounds at the same concentrations. Immune assay data suggest the possibility of seasonal effects at low doses. We present a multiple-level model to help interpret the data in the context of human health and biological conservation concerns. We discuss six testing deficiencies of currently registered pesticides, and suggest areas of human health concerns if present trends in pesticide use continue.

Protective effects of vitamin E against lead-induced deterioration of membrane associated type-I iodothyronine 5'-monodeiodinase (5'D-I) activity in male mice

The protective role of vitamin E (vit E) on lead-induced thyroid dysfunction with special reference to type-I iodothyronine 5'-monodeiodinase (5'D-I) activity in mice liver was investigated. Daily intraperitoneal (i.p.) injection of lead acetate (0.5 mg/kg body weight) for 30 days significantly decreased serum 3,3',5-triiodothyronine (T3) concentration and hepatic 5'D-I activity. Furthermore, lead significantly increased peroxidative reactions involving membrane components (lipid peroxidation, LPO) while the activities of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) were decreased in mouse liver. Simultaneous administration of vit E (5 mg/kg body weight) and 0.5 mg/kg body weight of lead restored thyroid function in mice by maintaining normal hepatic 5'D-I activity and serum thyroid hormone concentrations. It also prevented increase in LPO and inhibition of SOD and CAT activities in liver. We suggest that the intact membrane structure is a must for 5'D-I activity and the administration of vit E may prevent the lead induced thyroid dysfunction by maintaining membrane architecture.

Dimethoate inhibits extrathyroidal 5'-monodeiodination of thyroxine to 3,3',5-triiodothyronine in mice: the possible involvement of the lipid peroxidative process

The effects of daily administration of dimethoate (2, 4 and 8 mg/kg body weight for 30 days) on thyroid function in mice were investigated. While serum triiodothyronine (T3) concentration was decreased significantly, serum thyroxine (T4) was increased in the medium and highest dose treated groups. However, the serum concentration of thyrotropin was unaltered. Hepatic type-I iodothyronine 5'-monodeiodinase (5'-D) enzyme activity was depressed by the two higher doses of dimethoate. These observations suggest that dimethoate-induced alterations in thyroid function are not mediated through the hypophyseal thyroid axis, but through the changes in extrathyroidal conversion of T4 to T3. To correlate the lipid peroxidation (LPO) with 5'-D activity, hepatic LPO and the activity of antioxidant enzymes, i.e. superoxide dismutase (SOD) and catalase (CAT), were studied. The pesticide increased the activity of SOD and CAT along with hepatic lipid peroxidation. The possible involvement of the lipoperoxidative process in the inhibition of 5'-D activity has been suggested.