Effects of single and repeated administration of endosulfan on behaviour and its interaction with centrally acting drugs in experimental animals: a mini review

Endosulfan induces reproductive & genotoxic effect in male and female Swiss albino mice

BACKGROUND

Toxicity by pesticide has become a global health issue and leaves a harmful impact on human health via various ways. The people exposed to pesticides in the rural population get affected by the harmful effects of it as they enter the human body system through skin, inhalation, oral administration, food chain and many more ways. The present work is designed to study the toxic effect of endosulfan in male (n=30) and female (n=30) Swiss albino mice. Endosulfan was administered by oral gavage (oral administration) method, at the dose of 3.5 mg/Kg body weight daily for period of 3 weeks, 5 weeks and 7 weeks. After the completion of the treatment, the mice were sacrificed and their ovary and testis tissues were dissected out to check the degeneration. The blood was collected for karyotyping, biochemical and hormonal analysis of pesticide induced genotoxicity. After 7 weeks of administration with Endosulfan, various abnormalities were observed in male and female mice.

RESULTS

Treatment with endosulfan at the dose of 3.5 mg/Kg body weight caused a higher degree of degeneration in the reproductive organ of Swiss albino mice . Treatment by this pesticide generated degeneration in long duration of dosage for 3,5 and 7 weeks. Ovaries of endosulfan administered groups showed degenerated germinal epithelium, Graffian follicles and corpus luteum. In testis of endosulfan treated mice, microscopic examination showed that there is significant damage and reduction in the tissue of seminiferous tubules and primordial germ cells. High degree of degeneration caused the disarrangement and deformation of spermatogonia with the decrease in the number of Sertoli cells. Biochemical and hormonal properties was also affected by endosulfan treatment. There was significant 5 folds decrease in the testosterone value of endosulfan in 7 weeks treated mice in comparison to control (p < 0.0001) and similarly there was significant elevation in the estrogen levels found in 7th week endosulfan treated mice. It also influenced the level of free radicals as there was significant decrease (p < 0.0001) in the value in catalase levels in 7 weeks endosulfan treated male and female mice, while significant (p < 0.0001) increase in the values of lipid peroxidation levels as 8 folds and 10 folds in 7 weeks endosulfan treated male and female Swiss albino mice respectively. This study hence speculates that the endosulfan exposed population are at the risk of reproductive health hazards.

CONCLUSIONS

The present study thus concludes that, endosulfan after 7 weeks of exposure caused significant reproductive damage to both male and female Swiss albino mice groups. Moreover, the karyotyping study also correlated the genotoxic damage in the mice.

Exposure to endosulfan can cause long term effects on general biology, including the reproductive system of mice

Increased infertility in humans is attributed to the increased use of environmental chemicals in the last several decades. Various studies have identified pesticides as one of the causes of reproductive toxicity. In a previous study, infertility was observed in male mice due to testicular atrophy and decreased sperm count when a sublethal dose of endosulfan (3 mg/kg) with a serum concentration of 23 μg/L was used. However, the serum concentration of endosulfan was much higher (up to 500 μg/L) in people living in endosulfan-exposed areas compared to the one used in the investigation. To mimic the situation in an experimental setup, mice were exposed to 5 mg/kg body weight of endosulfan, and reproductive toxicity and long-term impact on the general biology of animals were examined. HPLC analysis revealed a serum concentration of ∼50 μg/L of endosulfan after 24 h endosulfan exposure affected the normal physiology of mice. Histopathological studies suggest a persistent, severe effect on reproductive organs where vacuole degeneration of basal germinal epithelial cells and degradation of the interstitial matrix were observed in testes. Ovaries showed a reduction in the number of mature Graafian follicles. At the same time, mild vacuolation in liver hepatocytes and changes in the architecture of the lungs were observed. Endosulfan exposure induced DNA damage and mutations in germ cells at the molecular level. Interestingly, even after 8 months of endosulfan exposure, we observed increased DNA breaks in reproductive tissues. An increased DNA Ligase III expression was also observed, consistent with reported elevated levels of MMEJ-mediated repair. Further, we observed the generation of tumors in a few of the treated mice with time. Thus, the study not only explores the changes in the general biology of the mice upon exposure to endosulfan but also describes the molecular mechanism of its long-term effects.

Protective effect of Catharanthus roseus plant extracts against endosulfan and its isomers induced impacts on non-targeted insect model, Drosophila melanogaster and live brain cell imaging

Endosulfan has been recognized as a highly controversial pesticide due to its acute toxicity, potential bioaccumulation, persistency, and long-range atmospheric transport. Several plant extracts act as antioxidant agents against wide-range of pesticide toxicity hazards through the free radicals scavenging properties. Plants' secondary metabolites are considered as efficient protective agents against various cellular toxic injuries. Understanding these properties of botanicals, several researchers currently focused on the detoxification and ameliorative potency of plant extracts against highly toxic chemicals. In our studies, we focused on the endosulfan total and its isomers (alpha and beta) induced changes on Drosophila melanogaster and their ameliorative effects by co-administrated with methanolic and aqueous extracts of Catharanthus roseus whole plant. We selected the 1/5th EC₅₀ concentration of alpha-endosulfan, beta-endosulfan, and endosulfan (total) and co-administrated with 1/50th EC₅₀ concentration of aqueous and methanolic extracts and evaluated their ameliorative effects, in terms of verifying the life stage activities, protein profiling and also by using live brain cells imaging. We finally concluded that, the methanolic and aqueous extracts inhibit the toxic impacts caused by endosulfan and its isomers and also increasing the survival rate of the test organism.

Remedial potential of bacterial and fungal strains (Bacillus subtilis, Aspergillus niger, Aspergillus flavus and Penicillium chrysogenum) against organochlorine insecticide Endosulfan

Endosulfan, an organochlorine insecticide, is known to cause detrimental effects to the environment and human health due to its excessive usage. Its highly toxic nature calls for an environmental-friendly approach for its detoxification. Environmental transformation of Endosulfan was assessed through biodegradation by isolated and cultured soil microbes (Bacillus subtilis (BS), Aspergillus niger (AN), Aspergillus flavus (AF) and Penicillium chrysogenum (PC)). Degradation of 10 mg/L Endosulfan was determined in aqueous solution at regular time intervals and analysed by gas chromatography-mass spectrometry for 35 days. BS and AN displayed substantial potential to degrade Endosulfan and subsequently transform it into its daughter products (95 and 77%, respectively). Endosulfan transformation followed first-order reaction kinetics. Chromatogram peaks revealed less toxic metabolites by Endosulfan transformation (Endosulfan diol, Endosulfan ether, Endosulfan hydroxyether and Endosulfan lactone). Half-life of Endosulfan obtained by various strains utilised in the experiments was in the order, PC (69) > AF (34.6) > AN (17.3) > BS (11.5) days. Statistical analysis was performed in MINITAB to evaluate the significance of results. Bioaugmentation of contaminated sites with such efficient microbes can facilitate rapid pesticide transformation and decontamination of the environment.

Mechanistic Interplay Between Autophagy and Apoptotic Signaling in Endosulfan-Induced Dopaminergic Neurotoxicity: Relevance to the Adverse Outcome Pathway in Pesticide Neurotoxicity

Chronic exposure to pesticides is implicated in the etiopathogenesis of Parkinson's disease (PD). Previously, we showed that dieldrin induces dopaminergic neurotoxicity by activating a cascade of apoptotic signaling pathways in experimental models of PD. Here, we systematically investigated endosulfan's effect on the interplay between apoptosis and autophagy in dopaminergic neuronal cell models of PD. Exposing N27 dopaminergic neuronal cells to endosulfan rapidly induced autophagy, indicated by an increased number of autophagosomes and LC3-II accumulation. Prolonged endosulfan exposure (>9 h) triggered apoptotic signaling, including caspase-2 and -3 activation and protein kinase C delta (PKCδ) proteolytic activation, ultimately leading to cell death, thus demonstrating that autophagy precedes apoptosis during endosulfan neurotoxicity. Furthermore, inhibiting autophagy with wortmannin, a phosphoinositide 3-kinase inhibitor, potentiated endosulfan-induced apoptosis, suggesting that autophagy is an early protective response against endosulfan. Additionally, Beclin-1, a major regulator of autophagy, was cleaved during the initiation of apoptotic cell death, and the cleavage was predominantly mediated by caspase-2. Also, caspase-2 and caspase-3 inhibitors effectively blocked endosulfan-induced apoptotic cell death. CRISPR/Cas9-based stable knockdown of PKCδ significantly attenuated endosulfan-induced caspase-3 activation, indicating that the kinase serves as a regulatory switch for apoptosis. Additional studies in primary mesencephalic neuronal cultures confirmed endosulfan's effect on autophagy and neuronal degeneration. Collectively, our results demonstrate that a functional interplay between autophagy and apoptosis dictate pesticide-induced neurodegenerative processes in dopaminergic neuronal cells. Our study provides insight into cell death mechanisms in environmentally linked neurodegenerative diseases.

Different effects of α-endosulfan, β-endosulfan, and endosulfan sulfate on sex hormone levels, metabolic profile and oxidative stress in adult mice testes

In the environment, endosulfan persists in forms of two isomers (α and β) and a toxic metabolite, endosulfan sulfate. The toxicity of endosulfan on various mammalian tissues has been investigated, but whether the different isomers and metabolites of endosulfans affect mammalian reproductive function remains unclear. This study is aimed to elucidate the different toxicological effects of α-endosulfan, β-endosulfan, and endosulfan sulfate on adult mice testes. We found that the three endosulfans (α endosulfan, β endosulfan and endosulfan sulfate) altered serum sex steroid hormone levels, and changed expression of steroidogenesis genes. By comparing results of ¹H-NMR and LC-MS/MS metabolomics between samples treated with different endosulfans, we found that endosulfans changed levels of metabolites involved in energy metabolism and oxidative stress, and these were associated with the imbalance of sex sterol hormone synthesis. Moreover, endosulfan isomers and sulfate metabolite treatment disrupted the mice testicular antioxidant systems and caused an increase in lipid peroxidation. Interestingly, the three endosulfans tested in this study each yielded different effects on serum sex hormone levels and testicular metabolic profiles in the adult mice. Beta-endosulfan exposure caused the strongest disturbance in the testes compared to the other endosulfans, with significantly higher testosterone levels and more pronounced changes to endogenous metabolites. Taken together, we identified the different effects of endosulfans on the testis by exposing mice to α endosulfan, β endosulfan and endosulfan sulfate, and we found that changes in sex sterol hormone levels induced by treatment with endosulfans were correlated to changes in endogenous metabolites. These findings provide new insight into mechanism of endosulfan-induced testicular toxicity.

Discrepant effects of α-endosulfan, β-endosulfan, and endosulfan sulfate on oxidative stress and energy metabolism in the livers and kidneys of mice

Endosulfan, an organochloride pesticide, has been used for many commercial purposes. Endosulfan is composed of two isomers, α-endosulfan and β-endosulfan. In biological and soil systems, endosulfan is metabolized into endosulfan sulfate. In this study, the different toxicological effects of α-endosulfan, β-endosulfan, and endosulfan sulfate on the livers and kidneys of mice were comprehensively investigated. The results demonstrated that both endosulfan isomers and endosulfan sulfate disturbed the hepatic and renal antioxidant systems. Furthermore, ¹H NMR metabolomics analysis revealed that endogenous metabolites involved in oxidative stress and energy metabolism were altered after exposure to these compounds. In the liver, the changes in hepatic endogenous metabolites and the induction of hepatic CYP450 mRNA isoforms were similar among mice treated with the three compounds, and the sulfate metabolite was the exclusive exogenous compound detected. Therefore, the metabolism of α- and β-endosulfan to endosulfan sulfate is likely the main cause of toxicological effects in the livers of mice. However, in kidneys, the changes in the metabolome and in CYP450 mRNA expression induced by α-endosulfan and β-endosulfan were stereoselective. Additionally, endosulfan sulfate, which induced a significant increase of renal Cyp3a11, showed a more robust disturbance of renal metabolites than either of the two isomers. These findings revealed that more attention should be given to the toxicological evaluation of endosulfan sulfate in the future.

Endosulfan Degradation by Selected Strains of Plant Growth Promoting Rhizobacteria

Sixty endosulfan tolerant bacterial strains were isolated from pesticide stressed agricultural soils. Five most tolerant strains were tested for plant growth promoting (PGP) activities and endosulfan degradation under different optimizing conditions in broth and soil. The strains PRB101 and PRB77 were the most efficient in terms of endosulfan degradation and PGP activities and showed solubilization indexes of 3.3 and 3.1 mm, indole acetic acid production of 71 and 68 μg mL^-1, siderophore zones of 13 mm each at the recommended dosage, respectively. Hydrogen cyanide and ammonia production remained unaffected in the presence of endosulfan. PRB101 and PRB77 strains were able to degrade 74% and 70% of endosulfan in broth and 67% and 63% in soil, respectively. Based on 16S rDNA analysis, the strains PRB101 and PRB77 exhibited 99% homology with Bacillus sp. KF984414 and Bacillus sp. LN849696, respectively.

Use of Ca-alginate immobilized Pseudomonas aeruginosa for repeated batch and continuous degradation of Endosulfan

The current investigation is taken up with the aim of studying repeated batch and continuous degradation of Endosulfan, using Ca-alginate immobilized cells of Pseudomonas aeruginosa isolated from an agricultural soil. The work involves the study of genes and enzymes involved in the degradation of the pesticide and was carried out with an objective of reducing the toxicity of Endosulfan by degrading it to less toxic metabolites. The long-term stability of Endosulfan degradation was studied during its repeated batch degradation, carried out over a period of 35 days. Immobilized cells of Ps. aeruginosa were able to show 60 % degradation of Endosulfan at the end of the 35th cycle with a cell leakage of 642 × 10⁴ Cfu/mL. During continuous treatment, with 2 % concentration of Endosulfan, 100 % degradation was recorded up to 100 mL/h flow rate and with 10 % concentration of the Endosulfan, and 100 and 85 % degradation was recorded at 20 mL/h flow rate and 100 mL/h flow rate, respectively. After degradation of Endosulfan, products were extracted from a large amount of spent medium using two volumes of ethyl acetate and subjected to the LC–MS analysis. Endosulfan lactone and Endosulfan ether were the products of degradation detected by the LCMS analysis. Plasmid curing experiments indicated that genes responsible for the degradation of Endosulfan are present on the chromosome and not on the plasmid, as growth of Ps. aeruginosa was observed on modified non-sulfur medium with Endosulfan after the plasmid was cured with ethidium bromide. The results of PCR indicated that there is no amplified product of ~1350 bp expected for esd gene, in Ps. aeruginosa, although there were some non-specific bands. Enzymatic degradation studies indicated that the enzymes involved in the degradation of Endosulfan are intracellular. With this investigation, it was indicated that immobilized cells of Ps.aeruginosa have the potential to be used in the bioremediation of water contaminated with Endosulfan.

Gamma radiolytic decomposition of endosulfan in aerated solution: the role of carbonate radical

The present study elaborates the removal of endosulfan, an emerging water pollutant and potential carcinogenic, in aerated solution. The influence of Cl(-), NO3 (-), NO2 (-), CO3 (2-), HCO3 (-), SO3 (2-), and humic acid was assessed on the radiolytic degradation of endosulfan. A strong inhibition on the radiolytic degradation of endosulfan was observed in the presence of NO3 (-), NO2 (-), and SO3 (2-). Instead, a slight increase in the removal efficiency of endosulfan was observed at high concentrations of CO3 (2-) and HCO3 (-). The formation of CO3 (•-) in radiolytic degradation of endosulfan in the presence of CO3 (2-) and HCO3 (-) was demonstrated by adding SO3 (2-) that rapidly react with CO3 (•-). The results indicate that CO3 (•-) formed from the reactions of CO3 (2-) and HCO3 (-) and commonly found in natural water can play an important role in the degradation of endosulfan and other sulfur containing electron-rich compounds. The study showed faster degradation of endosulfan at lower concentration compared to high concentration and removal was found to follow pseudo-first-order kinetic. Endosulfan ether was found as the main degradation product and degradation pathway was found to be initiated at the S=O bond of endosulfan. The efficiency of gamma irradiation in the removal of endosulfan was examined in terms of formation of short chain organic acids and chloride ion accumulation.

Endosulfan Induces CYP1A1 Expression Mediated through Aryl Hydrocarbon Receptor Signal Transduction by Protein Kinase C

CYP1A1 is a phase I xenobiotic-metabolizing enzyme whose expression is mainly driven by AhR. Endosulfan is an organochlorine pesticide used agriculturally for a wide range of crops. In this study, we investigated the effect of endosulfan on CYP1A1 expression and regulation. Endosulfan significantly increased CYP1A1 enzyme activity as well as mRNA and protein levels. In addition, endosulfan markedly induced XRE transcriptional activity. CH-223191, an AhR antagonist, blocked the endosulfan-induced increase in CYP1A1 mRNA and protein expression. Moreover, endosulfan did not induce CYP1A1 gene expression in AhR-deficient mutant cells. Furthermore, endosulfan enhanced the phosphorylation of calcium calmodulin (CaM)-dependent protein kinase (CaMK) and protein kinase C (PKC). In conclusion, endosulfan-induced up-regulation of CYP1A1 is associated with AhR activation, which may be mediated by PKC-dependent pathways.

Integrative genomic and proteomic profiling of human neuroblastoma SH-SY5Y cells reveals signatures of endosulfan exposure

Endosulfan, an organochlorine pesticide, is known to induce multiple disorders/abnormalities including neuro-degenerative disorders in many animal species. However, the molecular mechanism of endosulfan induced neuronal alterations is still not well understood. In the present study, the effect of sub-lethal concentration of endosulfan (3 μM) on human neuroblastoma cells (SH-SY5Y) was investigated using genomic and proteomic approaches. Microarray and 2D-PAGE followed by MALDI-TOF-MS analysis revealed differential expression of 831 transcripts and 16 proteins in exposed cells. A gene ontology enrichment analysis revealed that the differentially expressed genes and proteins were involved in variety of cellular events such as neuronal developmental pathway, immune response, cell differentiation, apoptosis, transmission of nerve impulse, axonogenesis, etc. The present study attempted to explore the possible molecular mechanism of endosulfan induced neuronal alterations in SH-SY5Y cells using an integrated genomic and proteomic approach. Based on the gene and protein profile possible mechanisms underlying endosulfan neurotoxicity were predicted.

Role of aqueous electron and hydroxyl radical in the removal of endosulfan from aqueous solution using gamma irradiation

The removal of endosulfan, an emerging water pollutant, from water was investigated using gamma irradiation based advanced oxidation and reduction processes (AORPs). A significant removal, 97% of initially 1.0 μM endosulfan was achieved at an absorbed dose of 1020 Gy. The removal of endosulfan by gamma-rays irradiation was influenced by an absorbed dose and significantly increased in the presence of aqueous electron (eaq(-)). However, efficiency of the process was inhibited in the presence of eaq(-) scavengers, such as N2O, NO3(-), acid, and Fe(3+). The observed dose constant decreased while radiation yield (G-value) increased with increasing initial concentrations of the target contaminant and decreasing dose-rate. The removal efficiency of endosulfan II was lower than endosulfan I. The degradation mechanism of endosulfan by the AORPs was proposed showing that reductive pathways involving eaq(-) started at the chlorine attached to the ring while oxidative pathway was initiated due to attack of hydroxyl radical at the SO bond. The mass balance showed 95% loss of chloride from endosulfan at an absorbed dose of 1020 Gy. The formation of chloride and acetate suggest that gamma irradiation based AORPs are potential methods for the removal of endosulfan and its by-products from contaminated water.

Uptake and accumulation of endosulfan isomers and its metabolite endosulfan sulfate in naturally growing plants of contaminated area

Endosulfan isomers (α+β) and its main metabolite endosulfan sulfate were analyzed in naturally growing vegetation of pesticide contaminated area in Ghaziabad, India. Seven species of dominating plants were collected at different locations within the contaminated area. Endosulfan residues from plant parts and soil were extracted and determined by a gas chromatograph equipped with 63Ni electron capture detector (GC-ECD). Endosulfan isomers and endosulfan sulfate were present in almost all soil and plant samples. The concentration of total endosulfan in plant and soil samples analyzed ranged from 14 to 343ng g(-1) and 13 to 938ng g(-1) respectively. Out of seven plant species studied, Vetiveria zizanioides (Khus Khus) and Sphenoclea zeylamica (Chikenspike) showed the highest and lowest accumulation respectively, with a significant difference at p<0.01 level. Vetiveria zizanioides and Digitaria longiflora (Crab grass) could accumulate considerable levels of endosulfan isomers (α+β) (343 and 163ng g(-1) respectively) and endosulfan sulfate (21 and 2ng g(-1), respectively). The outcomes of the study reflect the value of test species in monitoring purposes and their potential for remediation of contaminated sites.

Development and characterization of a new gill cell line from air breathing fish Channa striatus (Bloch 1793) and its application in toxicology: direct comparison to the acute fish toxicity

A new cell line, Channa striatus gill (CSG), derived from the gill tissue of murrel, was established and characterized. The CSG cell line was maintained in Leibovitz's L-15 supplemented with 10% fetal bovine serum and has been subcultured more than 92 times. This cell line was able to grow in a range of temperatures from 22 to 32°C with optimal growth at 28°C. The plating efficiency was very high (52.21%) and doubling time was approximately 37h. The gill cell line was cryopreserved at different passage levels and revived successfully with 85% survival. Polymerase chain reaction amplification of mitochondrial 16S rRNA using primer specific to C. striatus confirmed the origin of this cell line from murrel. The cell line was further characterized by immunocytochemical analysis, chromosome number, transfection and mycoplasma detection. The cytotoxicity of endosulfan was assessed in CSG cell line using apoptosis assay, comet assay, mitochondrial alteration and five other endpoints such as Rhodamine 123 uptake, 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, neutral red assay, Alamar Blue assay and Methylene Blue protein assay. Acute toxicity study on fish was conducted by exposing murrel for 96h to endosulfan under static conditions. Statistical analysis revealed good correlation with r(2)=0.972-0.997 among the five endpoints. Linear correlations between the in vivo lethal concentration 50 (LC50) and each in vitro effective concentration 50 (EC50) were highly significant. The present study highlights the development of a new gill cell line from an air breathing fish that could be used as an alternative in vitro tools for studying pesticide toxicity in fish.

Mycoremediation of endosulfan and its metabolites in aqueous medium and soil by Botryosphaeria laricina JAS6 and Aspergillus tamarii JAS9

Microbial degradation offers an efficient and ecofriendly approach to remove toxicants from the contaminated environments. Botryosphaeria laricina JAS6 and Aspergillus tamarii JAS9 were capable of degrading endosulfan and their metabolites which were isolated through enrichment technique. Both the strains were able to withstand an exposure of 1300 mg/L and showed luxuriant growth at 1000 mg/L of endosulfan. The change in pH in the culture broth was from 6.8 to 3.4 and 3.8 during growth kinetic studies of JAS6 and JAS9 strains, respectively upon biological degradation of endosulfan. The degradation of endosulfan by JAS6 and JAS9 strains were examined by HPLC. The biodegradation rate constant (k) and the initial concentration were reduced by 50% (DT50) which was determined by first and pseudo first order kinetic models. In the present investigation it has been revealed that Botryosphaeria laricina JAS6 and Aspergillus tamarii JAS9 possessing endosulfan degrading capability are being reported for the first time. These findings confirm the degradation of endosulfan by JAS6 and JAS9 strains which were accompanied by significant reduction in the toxicity and could be used as remedial measure in contaminated environments.

Reductive transformation of endosulfan in aqueous phase using magnesium-palladium bimetallic systems: a comparative study

The efficiencies of reductive transformation of endosulfan by bimetallic systems consisting of zerovalent magnesium (Mg(0)) as the electron donor and three forms of palladium as the catalyst (Pd(0)-alumina, Pd(0)-carbon and Pd-K(2)PdCl(6)) were compared in this investigation. Results revealed that both Pd(0)-alumina and Pd(0)-carbon were able to remove 90 and 93% of 10 mg L(-1) of endosulfan, respectively in 30 min with the concomitant accumulation of trace concentrations of partially chlorinated compounds in the reaction medium. Removal of endosulfan followed first-order kinetics and the rate constant (k(obs)) value was computed to be 0.2 min(-1) for both Pd(0)-alumina and Pd(0)-carbon. Pd(0)-carbon was relatively more stable and reusable in comparison to Pd(0)-alumina. More than 99% of 10 mg L(-1) endosulfan was converted to hydrocarbon end product by Pd-K(2)PdCl(6) system within 6 min of reaction. The formation of hydrocarbon end product suggested desulfurization and complete dechlorination of endosulfan. The efficiencies of removal of α and β endosulfan isomers were nearly the same in reaction media containing acetone or Tween 80 as the pesticide solubilizing agents. Results obtained in this study suggest the possibility of developing a reactor containing immobilized palladium for the treatment of water contaminated with endosulfan.

Enrichment and isolation of endosulfan-degrading microorganism from tropical acid soil

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the enrichment and isolation of a microbial culture capable of degrading endosulfan with minimal production of endosulfan sulfate, the toxic metabolite of endosulfan, from tropical acid soil. Enrichment was achieved by using the insecticide as sole sulfur source. The enriched microbial culture, SKL-1, later identified as Pseudomonas aeruginosa, degraded up to 50.25 and 69.77 % of alpha and beta endosulfan, respectively in 20 days. Percentage of bioformation of endosulfan sulfate to total formation was 2.12% by the 20th day of incubation. Degradation of the insecticide was concomitant with bacterial growth reaching up to an optical density of 600 nm (OD600) 2.34 and aryl sulfatase activity of the broth reaching up to 23.93 microg pNP/mL/hr. The results of this study suggest that this novel strain is a valuable source of potent endosulfan-degrading enzymes for use in enzymatic bioremediation. Further, the increase in aryl sulfatase activity of the broth with the increase in degradation of endosulfan suggests the probable involvement of the enzyme in the transformation of endosulfan to its metabolites.

Endosulfan acute toxicity in Bufo bufo gills: ultrastructural changes and nitric oxide synthase localization

Endosulfan is an organochlorine pesticide used in agriculture for a wide range of crops. Endosulfan concentrations of up to 0.7 mg/L can be found in ponds and streams near sprayed agricultural fields. We investigated the short-term toxicity of endosulfan in common toad (Bufo bufo) tadpoles after 24, 48, and 96 h of exposure. Acute toxicity was evaluated at nominal concentrations ranging from 0.01 to 0.6 mg/L: concentrations that could be found after the application of pesticide. Our results show that 0.43 mg/L of endosulfan caused 50% mortality (LC(50)). The effects of a sublethal endosulfan concentration (0.2mg/L) on gill apparatus morphology were evaluated by scanning and transmission electron microscopy. Immunohistochemical methods were also applied to detect the expression pattern of the inducible isoform of nitric oxide synthase (iNOS) in the gills using the confocal laser scanner microscope. Exposure to 0.2mg/L of endosulfan caused an apparent increase in mucus production, the occurrence of secretory vesicles and lamellar bodies, a widening of intercellular spaces and additionally there was evidence of an inflammatory response in the gill apparatus. The morphological alterations occurred after 24h and were more pronounced after 48 and 96 h of exposure. Altered morphology and increased mucus secretion indicate impaired gas exchange and osmoregulation in the gills. In addition, there was an increase of iNOS expression after 24 and 48 h which may reflect hypoxia and inflammation in the gill epithelium. Our results clearly indicate that short-term exposure to a sublethal concentration of endosulfan, near the high end of the environmental range, disrupts gill morphology and function in B. bufo tadpoles.

Studies on the genotoxicity of endosulfan in different tissues of fresh water fish Mystus vittatus using the comet assay

Endosulfan, a widely used organochlorine pesticide, is readily bio-accumulative in fishes and can be indirectly harmful to human populations. Limited efforts have been made to study long-term genotoxic effects of endosulfan in different tissues of fish using gentoxicity biomarkers. Therefore, the current investigation was undertaken to detect single-cell DNA strand breaks induced by endosulfan in the fresh water teleost fish Mystus vittatus using the comet assay. The LC(50) value of technical grade endosulfan was first determined for the fish species in a semistatic system, and on the basis of the LC(50) value, the sublethal and nonlethal concentrations were determined. The DNA damage was measured in gill, kidney, and erythrocytes as the percentage of DNA in comet tails of fish specimens exposed to the sublethal and nonlethal concentrations of endosulfan. In general, significant effects (p < 0.01) from both concentration and time of exposure were observed in exposed fishes. It was found that all the tissues at all concentrations exhibited the highest DNA damage on day 1, after which there was a nonlinear decline in the percentage of tail DNA. The comparison of DNA damage among the tissues at different concentrations could not show the sensitivity of particular tissue to endosulfan. The current study explored the utility of the comet assay for in vivo laboratory studies using fish species to screen the genotoxic potential of chemical agents.

Inflammatory effect of endosulfan via NF-κB activation in macrophages

Macrophages are essential for the inflammatory response process because they release a wide variety of proinflammatory mediators. Endosulfan is extremely toxic to invertebrates and has been implicated in various mammalian toxicities. However, its influence on production of cytokine or on the functions of macrophages is unclear. This study examined the effects of endosulfan on the production of nitric oxide (NO) and proinflammatory cytokines (IL-1beta, IL-6, TNF-alpha), and examined the molecular mechanism in macrophages. Exposing macrophages to endosulfan induced the production of NO and proinflammatory cytokines and the expression of these genes. The transient transfection and electrophoretic mobility shift assays with the NF-kappaB binding sites showed that the NF-kappaB transcription factor mediated the endosulfan-induced increase in the expression levels of iNOS and proinflammatory cytokines. These results show that endosulfan stimulates the production of NO and proinflammatory cytokines and can up-regulate the gene expression levels through NF-kappaB transactivation. Overall, these results suggest that endosulfan has inflammatory potential.

Biodegradation of α- and β-endosulfan by soil bacteria

Extensive applications of persistent organochlorine pesticides like endosulfan on cotton have led to the contamination of soil and water environments at several sites in Pakistan. Microbial degradation offers an effective approach to remove such toxicants from the environment. This study reports the isolation of highly efficient endosulfan degrading bacterial strains from soil. A total of 29 bacterial strains were isolated through enrichment technique from 15 specific sites using endosulfan as sole sulfur source. The strains differed substantially in their potential to degrade endosulfan in vitro ranging from 40 to 93% of the spiked amount (100 mg l(-1)). During the initial 3 days of incubation, there was very little degradation but it got accelerated as the incubation period proceeded. Biodegradation of endosulfan by these bacteria also resulted in substantial decrease in pH of the broth from 8.2 to 3.7 within 14 days of incubation. The utilization of endosulfan was accompanied by increased optical densities (OD(595)) of the broth ranging from 0.511 to 0.890. High performance liquid chromatography analyses revealed that endosulfan diol and endosulfan ether were among the products of endosulfan metabolism by these bacterial strains while endosulfan sulfate, a persistent and toxic metabolite of endosulfan, was not detected in any case. The presence of endosulfan diol and endosulfan ether in the bacterial metabolites was further confirmed by GC-MS. Abiotic degradation contributed up to 21% of the spiked amount. The three bacterial strains, Pseudomonas spinosa, P. aeruginosa, and Burkholderia cepacia, were the most efficient degraders of both alpha- and beta-endosulfan as they consumed more than 90% of the spiked amount (100 mg l(-1)) in the broth within 14 days of incubation. Maximum biodegradation by these three selected efficient bacterial strains was observed at an initial pH of 8.0 and at an incubation temperature of 30 degrees C. The results of this study may imply that these bacterial strains could be employed for bioremediation of endosulfan polluted soil and water environments.

DNA damage and mutagenicity induced by endosulfan and its metabolites

Endosulfan is a widely used broad-spectrum organochlorine pesticide, which acts as a contact and stomach poison. Nontarget species, such as cattle, fish, birds, and even humans, are also affected. Studies on the genotoxicity and mutagenicity of endosulfan have been inconsistent and nothing is known about the genotoxicity of its metabolites. In the present study, endosulfan (as a commercial isomeric mixture and as the alpha- and beta-isomers), and metabolites of endosulfan (the sulfate, lactone, ether, hydroxyether, and diol derivatives) were assayed for their ability to induce DNA damage in Chinese hamster ovary (CHO) cells and human lymphocytes using the Comet assay and were assayed for their mutagenicity using the Salmonella reversion assay (Ames test with TA98, TA97a, TA102, TA104, and TA100, with and without S9 activation). The compounds produced statistically significant (P < 0.01), concentration-dependent (0.25-10 microM) increases in DNA damage in both CHO cells and human lymphocytes. Endosulfan lactone caused the most DNA damage in CHO cells, while the isomeric mixture of endosulfan produced the greatest response in lymphocytes. The test compounds also were mutagenic in Salmonella strains at concentrations of 1-20 mug/plate (P < 0.05), with TA98 being the most sensitive strain and the diol and hydroxyether metabolites producing the highest responses. The results indicate that exposure to sublethal doses of endosulfan and its metabolites induces DNA damage and mutation. The contribution of the metabolites to the genotoxicity of the parent compound in Salmonella and mammalian cells, however, is unclear, and the pathways leading to bacterial mutation and mammalian cell DNA damage appear to differ.

Isolation of a soil bacterium capable of biodegradation and detoxification of endosulfan and endosulfan sulfate

Endosulfan, an endocrine disrupting chemical, is a widely used cyclodiene organochlorine pesticide worldwide, and it blocks neuronal GABA(A)-gated chloride channels in mammals and aquatic organisms. Endosulfan and its metabolites, such as endosulfan sulfate, are persistent in environments and are considered as toxic chemicals. For bioremediation of endosulfan, in this study, an attempt was made to isolate an endosulfan and endosulfan sulfate degrading bacterium from endosulfan-polluted agricultural soil. Through repetitive enrichment and successive subculture using endosulfan or endosulfan sulfate as the sole carbon source, a bacterium KS-2P was isolated. The KS-2P was identified as Pseudomonas sp. on the basis of the results of a 16S rDNA sequencing analysis and MIDI test. The degradation ratios for endosulfan or endosulfan sulfate in minimal medium containing endosulfan (23.5 microg mL(-1)) or endosulfan sulfate (21 microg mL(-1)) were 52% and 71%, respectively. Our results suggest that Pseudomonas sp. KS-2P has potential as a biocatalyst for endosulfan bioremediation.

Pesticides and Parkinson's disease--is there a link?

Parkinson's disease (PD) is an idiopathic disease of the nervous system characterized by progressive tremor, bradykinesia, rigidity, and postural instability. It has been postulated that exogenous toxicants, including pesticides, might be involved in the etiology of PD. In this article we present a comprehensive review of the published epidemiologic and toxicologic literature and critically evaluate whether a relationship exists between pesticide exposure and PD. From the epidemiologic literature, there does appear to be a relatively consistent relationship between pesticide exposure and PD. This relationship appears strongest for exposure to herbicides and insecticides, and after long durations of exposure. Toxicologic data suggest that paraquat and rotenone may have neurotoxic actions that potentially play a role in the development of PD, with limited data for other pesticides. However, both the epidemiology and toxicology studies were limited by methodologic weaknesses. Particular issues of current and future interest include multiple exposures (both pesticides and other exogenous toxicants), developmental exposures, and gene-environment interactions. At present, the weight of evidence is sufficient to conclude that a generic association between pesticide exposure and PD exists but is insufficient for concluding that this is a causal relationship or that such a relationship exists for any particular pesticide compound or combined pesticide and other exogenous toxicant exposure.

Development of a pressurized liquid extraction and clean-up procedure for the determination of α-endosulfan, β-endosulfan and endosulfan sulfate in aged contaminated Ethiopian soils

Pressurized liquid extraction (PLE) was investigated for the extraction of two endosulfan isomers and their metabolite from two real contaminated soil samples. PLE for 3x10min at 100 degrees C was proven to be more exhaustive than Soxhlet extraction (SOX) in one soil sample. On the other soil sample investigated the method was found to be equally exhaustive as SOX. The use of hazardous organic solvents such as n-hexane, toluene, and diethyl ether has been avoided in PLE and clean-up. Instead less toxic solvents have been used both at the extraction step (acetone/n-heptane) and clean-up step (ethyl acetate/n-heptane). A column Florisil clean-up procedure that consumes relatively low solvent volumes has been optimized and applied to purify soil extracts. The developed analytical procedure was validated by applying it to a certified reference soil material (CRM811-050). A recovery of 103% total endosulfan residue was obtained versus certified values.

Uptake and bioavailability of persistent organic pollutants by plants grown in contaminated soil

This paper assesses the uptake of persistent organic pollutants (POP's) into plants. In particular, uptake of alpha-endosulfan, beta-endosulfan and endosulfan sulfate from lettuce. The lettuce plants were grown on compost that had previously been contaminated at 10 and 50 microg g(-1) per POP. The soil was slurry spiked by adding the appropriate amount of POP in acetone in an approximate ratio of 1 ratio 2, w/v soil ratio solvent. The solvent was left to evaporate at ambient temperature for 24 hours. Lettuce plants were grown under artificial daylight for 12 hours a day. The influence of soil ageing on the recovery of POP's from spiked soil samples was also assessed. The average recovery of endosulfan compounds from slurry spiked soil (10, 20 and 40 microg g(-1)) was consistent (92.9 +/- 4.4% for n= 9). However, ageing of endosulfan compounds on the slurry spiked soil resulted in lower recoveries (average losses were 12.5% after 14 days ageing of slurry spiked soil). The uptake of POP's was assessed by measuring the amount of endosulfan compounds in roots and leaves from lettuce plants after 10, 20 and 33 days. In addition, control plants grown in uncontaminated soil were monitored and analysed. It was found that endosulfan compounds were present in the roots of all lettuce plants irrespective of soil spike level or age of plant. In the 33 day lettuce plants where the soil was spiked at the highest level (50 microg g(-1)) endosulfan compounds were determined in the leaves. The root to leaf ratio was found to be 3.1 for alpha-endosulfan, 46.0 for beta-endosulfan, and 24.3 for endosulfan sulfate. Spiked lettuce samples were subjected to in vitro gastrointestinal extraction to assess the bioavailability of endosulfan compounds. No detectable endosulfan compounds were determined in the gastric extracts while small quantities (range 0.06-0.12 microg g(-1)) were found in the intestinal extraction. All samples (soil and lettuce) were extracted using pressurised fluid extraction and analysed using gas chromatography with mass selective detection.

Toxicity and residues of endosulfan isomers

The continued availability of endosulfan is desirable for the production of cotton, and various other crops, because of its particular suitability for use in IPM and resistance management strategies. However, ongoing residue problems threaten the availability of the insecticide. Data described here suggest a beta-enriched insecticide is worthy of investigation as a useful alternative organochloride insecticide, having the advantages of reduced environmental and health concerns. The alpha-isomer of endosulfan is an order of magnitude more volatile than the beta-isomer, which is reflected in its initial rapid disappearance in the field. Approximately 70% of endosulfan is lost within 2 d of application due to volatilization. Based on volatilization kinetics, the volatilization of a beta-endosulfan formulation would be less than 5% that of commercial endosulfan. However, while it has been established that endosulfan vapor does lead to contamination of the riverine environment, this contamination is below residue levels recorded in rivers during the cotton growing season and, as such, reducing the volatility of the insecticide will only partially alleviate residue problems. Initial field trial results suggest that beta-endosulfan insecticide can achieve equivalent efficacy to commercial endosulfan at half the recommended label application rate; presumably this is a reflection of its containment on site in comparison to the more volatile commercial mix of isomers. An insecticide composed primarily of the beta-isomer would have reduced volatility and equivalent efficacy at lower application rates compared to the commercial mix of isomers, reducing offsite endosulfan residues. An important advantage of a beta-enriched insecticide would be its potential to minimize endosulfan residues in locally grown production animals. The predominant endosulfan residue in animal fat is endosulfate, accumulated after the animal ingests the metabolite while grazing on pastures contaminated by endosulfan spray drift. As the beta-isomer is oxidized on the surface of plants and by microbes at much lower rates than the alpha-isomer, endosulfate levels would be lower as a result of a contamination event with a beta-endosulfan-based insecticide compared to the commercial mix. Finally, acute toxicity against mammals of the alpha-isomer is more than three times that of the beta-isomer, and the neurotoxicity of the insecticide has been attributed to the alpha-isomer. Therefore, a beta-enriched insecticide will be less acutely and chronically toxic to agricultural workers than the commercially available insecticide. In conclusion, these properties suggest that the alpha-isomer contributes more significantly to the residue problems associated with the insecticide than the beta-isomer and that the use of a beta-isomer-based insecticide would reduce residue problems yet retain the advantages to IPM and resistant management strategies unique to the current endosulfan formulation.

Biodegradation kinetics of endosulfan by Fusarium ventricosum and a Pandoraea species

Endosulfan, classified as an organochlorine pesticide, is rated by the U.S. EPA as a Category 1 pesticide with extremely high acute toxicity. This study describes the biodegradation kinetics of endosulfan and the metabolic pathway utilized by Fusarium ventricosum and a Pandoraea sp. Complete disappearance of both alpha- and beta-endosulfan was observed during 12 days of incubation with F. ventricosum in flasks containing 100 mg L(-)(1) of endosulfan. The rate constants (k) for biodegradation of alpha- and beta-endosulfan by F. ventricosum using zero-order kinetics were 14.22 and 6.60 mg L(-)(1) day(-)(1), respectively. The Pandoraea sp. degraded about 95 and 100% of alpha- and beta-endosulfan, respectively, in 18 days of incubation in flasks spiked with 100 mg L(-)(1) of endosulfan. The rate constants (k) for biodegradation of alpha- and beta-endosulfan by the Pandoraea sp. were 8.19 and 3.78 mg L(-)(1) day(-)(1), respectively. Both fungal and bacterial strains formed less toxic endosulfan diol and endosulfan ether as metabolites during metabolism of endosulfan. The results of this study suggest that these novel strains may be used for the bioremediation of endosulfan-contaminated sites.

Enrichment and isolation of endosulfan-degrading microorganisms

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the isolation and identification of enriched microorganisms, capable of degrading endosulfan. Enrichment was achieved by using the insecticide as either the sole source of carbon or sulfur in parallel studies. Two strains each of fungi (F1 and F4) and bacteria (BF2 and B4) were selected using endosulfan as a sole carbon source. A Pandoraea species (Lin-3) previously isolated in our laboratory using lindane (gamma-HCH) as a carbon source was also screened for endosulfan degradation. F1 and F4 (Fusarium ventricosum) degraded alpha-endosulfan by as much as 82.2 and 91.1% and beta-endosulfan by 78.5 and 89.9%, respectively, within 15 d of incubation. Bacterial strains B4 and Lin-3 degraded alpha-endosulfan up to 79.6 and 81.8% and beta-endosulfan up to 83.9 and 86.8%, respectively, in 15 d. Among the bacterial strains isolated by providing endosulfan as a sulfur source, B4s and F4t degraded alpha-endosulfan by as much as 70.4 and 68.5% and beta-endosulfan by 70.4 and 70.8%, respectively, after 15 d. Degradation of the insecticide occurred concomitant with bacterial growth reaching an optical density (OD600) of 0.366 and 0.322 for B4 and Lin-3, respectively. High OD600 was also noted with the other bacterial strains utilizing endosulfan as a sulfur source. Fungal and bacterial strains significantly decreased the pH of the nutrient culture media while growing on endosulfan. The results of this study suggest that these novel strains are a valuable source of potent endosulfan-degrading enzymes for use in enzymatic bioremediation.

The effects of endosulfan and variable water temperature on survivorship and subsequent vulnerability to predation in Litoria citropa tadpoles

The effects of short-term exposure of stage 25 Litoria citropa tadpoles to sublethal concentrations of endosulfan in combination with either a stable or a variable temperature cycle (20+/-2 vs. 21+/-7.5 degrees C) were investigated. Both exposure to 0.8 microg/l endosulfan and the wider temperature range over 96 h had significant adverse effects on survivorship. In addition, variable water temperatures at the time of endosulfan exposure increased tadpoles' vulnerability to predation by odonates 24 days later, but only if they had also been exposed to endosulfan. This effect occurred despite maintenance of all tadpoles at 19+/-1 degrees C during the intervening 24 days. Correlates of fitness such as this represent a move towards more biologically relevant experimental endpoints. This is an important step if we are to gain an understanding of how exposure to agricultural chemicals may affect frog populations in the natural environment. The results indicate that a short, pulsed exposure to a sublethal concentration of endosulfan and extremes in temperature may then have long-term impacts on fitness.

Enrichment of an endosulfan-degrading mixed bacterial culture

An endosulfan-degrading mixed bacterial culture was enriched from soil with a history of endosulfan exposure. Enrichment was obtained by using the insecticide as the sole source of sulfur. Chemical hydrolysis was minimized by using strongly buffered culture medium (pH 6.6), and the detergent Tween 80 was included to emulsify the insecticide, thereby increasing the amount of endosulfan in contact with the bacteria. No growth occurred in control cultures in the absence of endosulfan. Degradation of the insecticide occurred concomitant with bacterial growth. The compound was both oxidized and hydrolyzed. The oxidation reaction favored the alpha isomer and produced endosulfate, a terminal pathway product. Hydrolysis involved a novel intermediate, tentatively identified as endosulfan monoaldehyde on the basis of gas chromatography-mass spectrometry and chemical derivatization results. The accumulation and decline of metabolites suggest that the parent compound was hydrolyzed to the putative monoaldehyde, thereby releasing the sulfite moiety required for growth. The monoaldehyde was then oxidized to endosulfan hydroxyether and further metabolized to (a) polar product(s). The cytochrome P450 inhibitor, piperonyl butoxide, did not prevent endosulfan oxidation or the formation of other metabolites. These results suggest that this mixed culture is worth investigating as a source of endosulfan-hydrolyzing enzymes for use in enzymatic bioremediation of endosulfan residues.